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At wits end Pages: 12Last

ascalise on Tue July 23, 2013 10:01 PM User is offline

Year: 2006
Make: Chevrolet
Model: Silverado 2500HD
Engine Size: 6.6L
Refrigerant Type: R134a
Ambient Temp: 95
Country of Origin: United States

Where to start? This is going to be a difficult and maybe confusing read since I'm not the best at writing. Let me first start by saying I am no A/C expert but have been successfully working on/fixing automotive ac's for myself and friend for about 12 years with nothing but success.

Now on to my problems that I can't seem to fix after 2 months and lots of money spent. About a year ago I bought this truck and the a/c worked perfectly fine up until about 2 months ago. I was coming home from a fishing lodge that I visit on the weekends and noticed that the compressor was cycling too often at highway speeds. As soon as I got home I found a leaky seal on my compressor. I figured, no big deal, I'll swap it out tomorrow and get it going again. So, the next day I run to the dealer, grab a compressor, and orifice tube. Was not able to pick up an accumulator at the dealer since they were out of stock. So, I visited a local 1-800Radiator location and picked up a Chinese unit. On the way home I stopped at Oreilly and grabbed a seal kit, 2 quarts of flush, 8oz of oil, and 3 cans of straight 134. As soon as I got home I tore the system apart and THOROUGHLY flushed everything. Once I had determined that everything was as clean as it was going to get I proceeded to replacing all seals (had been soaking in new fresh oil) in the system. I added what I thought was enough oil to replace what was lost in the old compressor and accumulator and buttoned everything up. I then hooked up the vac pump to the system and evacuated for about 30 minutes. I turned off the pump and waited about another 15 minutes just to make sure that I didn't lose any vacuum which would lead me to think there might have been a leak. I then began to charge using cans. I know, I know, not a good idea but it is 100* here during the summer and wanted a/c for work the next day. My system capacity is 25.6 ounces. I figure I lose about an ounce or so in every can when I purge hoses. I emptied two cans in to the system and a tad bit of the third. I put everything away and went for a ride and enjoyed ICE cold air. (About 39-40* at the vents on recirc 2 notches down from full fan speed on my automatic ac controls) All was perfect.

Fast forward to two weeks later:
I decided to put a power steering cooler on my truck to eliminate some obnoxious PS pump sounds. While I was working on that, I noticed that HUGE bolt had broken and come through my grill and proceeded to bury itself in my condenser. It was late, about 8:00 on friday so sourcing parts from the dealer over the weekend was out of the questions. I decided (big mistake) to buy a condenser at Advance Auto Parts. I brought it home, installed it (noticed it had much bigger tanks on the sides), flushed everything out again, replaced seals, etc etc, same as before. When it came time to charge it the A/C never cooled as quickly as it normally would while charging. It took almost 4 cans (48oz) nearly double the capacity of my system before I got decent vent temps. Now, I figured this had everything to do with the size of the tanks on the sides of the condenser. I didn't like this one bit. I drove it around for a couple of days like this while I had my factory condenser repaired at a local radiator shop. I picked up the repaired factory condenser, brought it home along with another new factory accumulator from the dealer, flushed, replaced seals, (by now I'm sure you know the routine) and charged 2 full cans then a tad of the third. The A/C never cooled well during charging or after from this day on.

Performance was as follows:
Took about 15 minutes to kinda cool the cab, where as it would usually be cooled in a matter of a few minutes.
Vent temps were consistently 55* unless truck has been running for 30 minutes or more.
Compressor would cycle as soon as engine hit 1500rpm or so at around 33psi on the low side.
Coldest vent temps were about 46 after cooling cab and letting truck idle for extended periods of time.
As soon as I was under way vent temps would rise to as high as 57*
Fresh (outside) air performance was/is worthless. Temp rises 10-15* on outside air. I understand it will be a little warmer due to weather but in the past it has always been within 5* or so in town and a couple degrees on the road.

Luckily for me my best friend has an identical truck only with manual a/c controls which are essentially the same thing but with knobs and sliders instead of knobs and buttons. It still has the same under dash HVAC box with the same evap and all electronics. Anyway, i asked to borrow his truck for a bit and brought it home and parked it next to mine and let them both cool down for over 4 hours. I put a set of gauges on both trucks and fired them up at the same time. (Here is where I am confused) His truck pulls the low side down to 35-40 within seconds whereas mine takes a very long time. Mine would hover around 60-70psi and VERY SLOWLY come down if the engine was revved. His high side pressure at the time was higher than mine was. His cabin cooled nearly immediately and mine was just a step below mediocre. Within 3-4 minutes his vent temp was about 40* and mine about 57* So, based off mine findings I figured maybe I had received a defective compressor and exchanged it the next day at the dealer for another new one. Came home, swapped compressor, started the routine, buttoned up, and charged. I ended up with the exact same symptoms. At this point, I was pretty pissed

I waited a few days then took it a mechanic with a recovery machine wanting it evacuated and charged to exactly factory spec. He examined the performance of the a/c system under the hood and said all was working perfectly fine and that my problem was inside. I told him there was nothing wrong inside (let's backup a step here) since i have visually checked function of all blend door actuators and even had the dealership reflash my a/c control module. He asked if he could check the function of all the blend door actuators with his scanner and I said sure, but I'm not going to pay for it. He ended up checking them anyway and verified that they were all working properly. He then proceeded to evac the system and charge to exactly 25.6oz. He said I had 1 ounce too much in the system. When I left there I think my vent temps had dropped about 2* across the board depending on conditions. So, still not fixed.

At this point, I decided I have to see/feel the evap and decided to cut a hole in the box and do the cabin filter retrofit mod while i was in there. Turns out evap was not very dirty except for in one corner there was very little mud. It was not very cold to touch after running for 15-20 minutes. Installed some filters and sealed/closed it up.

About 2 weeks later (getting hotter outside) I dug into again. Went ahead and decided I'm going to replace EVERYTHING minus the compressor. I called my buddy at the dealer and ordered a condenser, all hoses and lines, an accumulator, an orifice tube, and an evaporator core. I know, a stupid idea to replace everything but at this point i'm desperate for properly functioning air conditioning. Also thought it wouldnt hurt to visually inspect everything inside the HVAC box for proper sealing and blend door function. So last wednesday I began to tear the interior and dash out of my truck. Parts came in thursday. Around 8:55pm I opened the box the evap came in and noticed it was the wrong one. I about panicked. I knew the dealer would not have the correct one in stock and could not be without my truck for another week or waiting on an evap. I hauled ass to advance auto parts and picked one up. While, it is not 100% identical, it is close enough and there is no reason why it wouldn't work properly (unlike the condenser I had purchased there a month ago) By 2:30am friday morning I had it all back together dash and all. And guess what? SAME DAMN THING! I decided to bypass the low pressure switch and sit in the truck and hold it at 1500rpm. Like this it will get damn cold. 41-42* after a while (still not as quickly as it used to) but will freeze up the suction line and accumulator. It still does not cool well or quickly at all and cycles as soon as you get moving ~1500rpm and higher. Starts to cool off again at idle. At that point I didn't care anymore and when new truck shopping saturday. I quickly decided I wasn't going to go that route. I prefer my truck and my payments. So, I'm stuck. I did however today decide to get my original compressor resealed and tested to the tune of $60. That is now sitting here and i'm wondering if I should give that a try. I'm torn though. Like i said, when it has been sitting off a while it will take too long to bring the low side down but the High side is fine and the discharge line off the compressor will burn you if touch it within 20 seconds of starting up.

Anyway gentleman, I am desperate to find my problem. I have exhausted all of my options and put more money and time into this that I should have. I have no idea where to go from this point. I would most certainly appreciate any help or guidance. Also, i'm sure there were a few little things I left out as this has been a 2 month ordeal. Feel free to ask me any questions if there is something I may have left out. Sorry for the ridiculously long post. I've been contemplating posting here for a long while about these issues but don't usually like to bother people with my problems.

Thanks in advance,
Aaron Scalise

ascalise on Tue July 23, 2013 10:04 PM User is offline

Already realized I left something out. I bypassed heater core to make absolutely certain no hot air was in the box. Did this a couple days ago.

GM Tech on Tue July 23, 2013 10:15 PM User is offline

Is the orifice tube on an 06 still in condenser outlet? if so- are you using a condenser out designed OT- they are different from evap in OTs...Is it seated right?

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

ascalise on Tue July 23, 2013 10:16 PM User is offline

Yes it is in the line that comes off the condenser located right before the accumulator. I am using the factory condenser. Just replaced with another factory one last week. It is seated yes.


Edited: Tue July 23, 2013 at 10:17 PM by ascalise

GM Tech on Wed July 24, 2013 8:49 AM User is offline

Can C/K trucks still be plumbed backwards? or are there manifolds there- I've been away a few years-- if condenser is plumbed backwards- you get what OP is getting....funky results.

Make sure high side line from compressor feed TOP of condenser..to work right.

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

ascalise on Wed July 24, 2013 11:21 AM User is offline

I am assuming you mean the condenser being backwards, as in upside down. It can only be mounted one way. The high side line from the compressor goes to the top of the condenser.

webbch on Wed July 24, 2013 12:40 PM User is offlineView users profile

I think he means swapping the inlet/outlet connections on the condenser. In that case, flow direction would be reversed, which would mess up how the orifice tube functions. On my 90 Silverado, it's possible to plumb it in reverse because both ports are the same size, and close enough together that it wouldn't be difficult to accidentally reverse the connections.

An identical situation would occur if the OT was installed backwards, OR if it was installed into the wrong port on the condenser (again, not sure that would even be possible)

Edited: Wed July 24, 2013 at 1:49 PM by webbch

ascalise on Wed July 24, 2013 4:21 PM User is offline

The lines are not backwards. They are rigid aluminum lines and only go one way.

ascalise on Wed July 24, 2013 4:23 PM User is offline

Also the orifice tube is located nowhere near the condenser. It is in the line right before the accumulator and is inserted the right way.

iceman2555 on Wed July 24, 2013 7:16 PM User is offlineView users profile

The statement about the discharge line 'burning' after a period of time tends to work toward a restricted condenser. This could be the result of debris produced by the OE compressor when operated with an insufficient refrigerant level. This would also produce the less than cool evap and of course, lack of cabin cooling performance.

The Chinese accumulator from Advance could also be a contributing factor. We have encountered imported accumulators that do not flow the same amount of refrigerant as the OE units. The 'J' tube located inside the accumulator are not the same internal diameter as the OE unit and when the tube is bent to form the bottom of the "J" the tube actually severely restricts the flow of refrigerant. This reduces cooling efficiency but also reduces the amount of lubricant flowing thru the system....resulting in possible debris formulations....equals a restricted condenser. Also, did the post not indicate that the OE condenser was repaired. How as the unit repaired and in what location. The modern condenser is a diminishing flow unit and if tubes were removed or sealed, this could severely restrict the unit. Once more this restriction could result in loss of cooling efficiency.

If we assume (?) the system is properly charged, and the temperature of the discharge line does indeed increase in temperature...then the first test would be a temp drop test for the condenser. Typical drop should be in the high20's to low 30 degree. Max Air, High Blower ,Idle speed, Doors open. Allow to operate for 5-7 minutes prior to performing test. Also the statement that the compressor cycles when operated at high ways speeds.....this could also indicate a restricted condenser. The compressor (Denso) has a HPCO switch located in the rear head of the unit. Let me rephrase that...some of these units have a HPCO switch located in the compressor...others do not. Check to insure this. While there...check the Pressure Relief Valve to insure that it has not purged.

Can truly understand the frustration that comes from an extensive repair and then have the system not function as it should.

What type flush was used for this system? Curious to know? How was it removed from the system?

What type lubricant was added to the system and how much?

First thoughts would be toward a restricted condenser. If so, then this will need to be replaced.....and now the hard part. What damage has already occurred to the newly installed compressor and possible contamination to other components. One must decided at this point to continue to add/replace parts and hope for the best outcome or bite the bullet and completely repair the system and replace all parts necessary to insure a successful repair. My vote would be to perform the repair to insure a successful repair. Trying to replace this part...that part...and wishing for a performing system normally does not produce the desired effect.

Test the condenser....post back results and let's look at the system from that point. The discharge line (compressor to condenser) should not be so hot as to be uncomfortable to touch. Test the liquid line...should be warm....if near ambient temp....or cooler.....got a flow problem. Remove the plastic cover over the radiator and condenser. This will allow for easier access to the discharge line as it enters the condenser.

Let us know.


-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

ascalise on Wed July 24, 2013 8:12 PM User is offline

Quote
Originally posted by: iceman2555
The statement about the discharge line 'burning' after a period of time tends to work toward a restricted condenser. This could be the result of debris produced by the OE compressor when operated with an insufficient refrigerant level. This would also produce the less than cool evap and of course, lack of cabin cooling performance.



The Chinese accumulator from Advance could also be a contributing factor. We have encountered imported accumulators that do not flow the same amount of refrigerant as the OE units. The 'J' tube located inside the accumulator are not the same internal diameter as the OE unit and when the tube is bent to form the bottom of the "J" the tube actually severely restricts the flow of refrigerant. This reduces cooling efficiency but also reduces the amount of lubricant flowing thru the system....resulting in possible debris formulations....equals a restricted condenser. Also, did the post not indicate that the OE condenser was repaired. How as the unit repaired and in what location. The modern condenser is a diminishing flow unit and if tubes were removed or sealed, this could severely restrict the unit. Once more this restriction could result in loss of cooling efficiency.



If we assume (?) the system is properly charged, and the temperature of the discharge line does indeed increase in temperature...then the first test would be a temp drop test for the condenser. Typical drop should be in the high20's to low 30 degree. Max Air, High Blower ,Idle speed, Doors open. Allow to operate for 5-7 minutes prior to performing test. Also the statement that the compressor cycles when operated at high ways speeds.....this could also indicate a restricted condenser. The compressor (Denso) has a HPCO switch located in the rear head of the unit. Let me rephrase that...some of these units have a HPCO switch located in the compressor...others do not. Check to insure this. While there...check the Pressure Relief Valve to insure that it has not purged.



Can truly understand the frustration that comes from an extensive repair and then have the system not function as it should.



What type flush was used for this system? Curious to know? How was it removed from the system?



What type lubricant was added to the system and how much?



First thoughts would be toward a restricted condenser. If so, then this will need to be replaced.....and now the hard part. What damage has already occurred to the newly installed compressor and possible contamination to other components. One must decided at this point to continue to add/replace parts and hope for the best outcome or bite the bullet and completely repair the system and replace all parts necessary to insure a successful repair. My vote would be to perform the repair to insure a successful repair. Trying to replace this part...that part...and wishing for a performing system normally does not produce the desired effect.



Test the condenser....post back results and let's look at the system from that point. The discharge line (compressor to condenser) should not be so hot as to be uncomfortable to touch. Test the liquid line...should be warm....if near ambient temp....or cooler.....got a flow problem. Remove the plastic cover over the radiator and condenser. This will allow for easier access to the discharge line as it enters the condenser.



Let us know.


The discharge off the compressor will burn you immediately. As far as the accumulator goes it is a factory part, not from advance. The evap is from advance. As far as the condenser goes, yes it was repaired and put back into service. Keep in mind though EVERYTHING is new as of now. No flush has been done as it wasnt necessary. Last time i checked (the day after i had it all backtogether) there is about a 15* drop across the condenser. My compressor does not have a HPCO switch on it. The HPCO is a 3 wire unit that is on the discharge line directly off the compressor about 3" away on the discharge line. I used pag 46 oil in this sytem 8 oz total capacity.


Thanks,
Aaron

iceman2555 on Wed July 24, 2013 8:38 PM User is offlineView users profile

Was not able to pick up an accumulator at the dealer since they were out of stock. So, I visited a local 1-800Radiator location and picked up a Chinese unit.

This is the accumulator I spoke of.

I stopped at Oreilly and grabbed a seal kit, 2 quarts of flush, 8oz of oil, and 3 cans of straight 134.

This was the reason for the flush question.

From your statement...all the parts currently installed are new...except for the compressor.....correct. Were all these parts replaced at one time....or were they replaced at different intervals.

If the discharge line is extremely hot....there is a restriction in the inlet side of the condenser. This could account for both the cycling condition and the lack of proper cooling. Excuse my feeble mind...but is this a new GM/Delco condenser, the repaired OE condenser, or a condenser supplied by the dealer that may have been purchased from another source.

The condenser temp difference is a bit low. This is typical of a undercharged system or a cooling system problem. Does the temp of the liquid line appear to be the same as the discharge line....how was the difference of 15 degrees determined? What type tool was utilized?

Test with your fingers....determine if the two temps are about the same...as indicated...or the discharge is much cooler.

All this is, of course, dependent upon the system being completely recharged. The lubricant type and amount are correct.

Thanks for the info....just a bit more...should be able to ascertain the root cause. Two conflicting issues....the extreme temp of the discharge line....and the lack of temp drop across the condenser....both point in two different directions....but persistence will prevail.





-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

ascalise on Wed July 24, 2013 8:47 PM User is offline

Quote
Originally posted by: iceman2555
Was not able to pick up an accumulator at the dealer since they were out of stock. So, I visited a local 1-800Radiator location and picked up a Chinese unit.



This is the accumulator I spoke of.

This accumulator was installed when the original compressor leaked and was replaced.



I stopped at Oreilly and grabbed a seal kit, 2 quarts of flush, 8oz of oil, and 3 cans of straight 134.

This was done every time i messed with the system except for last week when all everything was replaced by the compressor.


This was the reason for the flush question.



From your statement...all the parts currently installed are new...except for the compressor.....correct. Were all these parts replaced at one time....or were they replaced at different intervals.

Correct. I replaced the compressor, accumulator, seals, and orifice tube the very first time.

If the discharge line is extremely hot....there is a restriction in the inlet side of the condenser. This could account for both the cycling condition and the lack of proper cooling.

It is hot, but not as hot as my buddies truck which cools perfectly.

Excuse my feeble mind...but is this a new GM/Delco condenser

Yes from the dealer. I even exchanged it a couple of weeks after i installed it thinking something could've been wrong with it.

the repaired OE condenser, or a condenser supplied by the dealer that may have been purchased from another source.

Yes I am currently running a brand new factory OE condenser.

Last Thursday I replaced absolutely everything in the system except for the 2 week old compressor. I drained the oil out of it and it looked the same as the day it went in. Absolutely perfect.



The condenser temp difference is a bit low. This is typical of a undercharged system or a cooling system problem. Does the temp of the liquid line appear to be the same as the discharge line....

Where would you like these measurements taken from?


how was the difference of 15 degrees determined? What type tool was utilized?

Infrared thermometer same distance away from each port on the condenser.


Test with your fingers....determine if the two temps are about the same...as indicated...or the discharge is much cooler.



All this is, of course, dependent upon the system being completely recharged. The lubricant type and amount are correct.



Thanks for the info....just a bit more...should be able to ascertain the root cause. Two conflicting issues....the extreme temp of the discharge line....and the lack of temp drop across the condenser....both point in two different directions....but persistence will prevail.


Thanks again,
Aaron

ascalise on Wed July 24, 2013 8:58 PM User is offline

Just realized I made a mistake. The compressor was replaced twice from the dealer. The condenser was replaced last Thursday with a factory unit.

iceman2555 on Wed July 24, 2013 9:07 PM User is offlineView users profile

How was the system prepared for these two new compressors? Where they flushed at that time? How much lubricant was added to the system with each compressor installation? What was the condition of the orifice tube and was it replaced or serviced with each new compressor? Was the accumulator replaced each time also?
Thanks

-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

ascalise on Wed July 24, 2013 9:09 PM User is offline

It was flushed and all seals were replaced along with the orifice tube. Oil was measured and replaced. Orifice tubes were all perfect when they came out. Accumulator was replaced all but when the new compressor was replaced with another new one.

How about we forget about everything prior to replacing the entire system if that makes anything easier?
I just don't see how at this point it makes any difference.

iceman2555 on Wed July 24, 2013 11:08 PM User is offlineView users profile

The discharge line should not be so hot as to burn you immediately or after an period of operational time.
Infra-red are prone for erroneous readings. Underhood temps can affect them drastically. Please post the actual temperatures recorded for each location. What were the vehicle test conditions? Difference in engine rpm/doors open/closed can make a large difference.

There are several options available at this time...unfortunately they both require time....others require time and cash....let's try the time only for now.

Insure that the system is totally and fully charged. No cans....the system should be charged with a J2788 machine or a weigh scale.

Start the vehicle....allow to operate for 5-7 minutes.....BOTH CABIN DOORS OPEN....MAX AIR....HIGH BLOWER....ENGINE AT IDLE.

Measure the inlet and outlet temps of the evaporator. After the orifice tube (cold side) and the outlet (before the accumulator). Record and post info. These two temps should be the same....exact...or within 3-5 degrees of each other. The outlet temp indicates the actual evap core temp within a few degrees and this can be compared to actual vent temps to determine system operations.

Measure the condenser inlet and outlet temps as close to the inlet as possible. Post info.

Measure the temp drop across the orifice tube. Post info.

Measure the center vent temperature and the temperature (ambient) approximately 12 inches in front of the condenser.

If possible post pressures...but temps will work as well.

Once this info is collected....repeat with the engine at 1500 PRM/MAX COOL/DOORS CLOSED/LOW OR SECOND BLOWER SPEED.

Let's see the info furnished by these components.

This is not an insurmountable event. We simply need to establish a time line for repairs....and operational conditions. Certain events must occur for a AC system to perform....we just need to determine the location of the 'glitch'.





-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson



Edited: Wed July 24, 2013 at 11:14 PM by iceman2555

ascalise on Wed July 24, 2013 11:42 PM User is offline

Quote
Originally posted by: iceman2555
The discharge line should not be so hot as to burn you immediately or after an period of operational time.

Infra-red are prone for erroneous readings. Underhood temps can affect them drastically. Please post the actual temperatures recorded for each location.

I understand this, especially in areas around airflow. Unfortunately I do not have a thermocouple.

What were the vehicle test conditions?

I am working on it as we speak. I evacuated once again and charged exactly 25.6oz with a new quality refrigerant scale just now. Ambient temp is 86*, cabin is 45.5 on recirc doors closed, engine idling. This is as cold as it will get with the low pressure switch plugged in. It cycles off about 28PSI low side. As of right now this instant gauges read 29/160. As soon as engine is revved anything above idle it just cycles more often.

Difference in engine rpm/doors open/closed can make a large difference.

There are several options available at this time...unfortunately they both require time....others require time and cash....let's try the time only for now.

Insure that the system is totally and fully charged. No cans....the system should be charged with a J2788 machine or a weigh scale.

See above.

Start the vehicle....allow to operate for 5-7 minutes.....BOTH CABIN DOORS OPEN....MAX AIR....HIGH BLOWER....ENGINE AT IDLE.

Truck has been running for 30+ minutes now since charged.

Measure the inlet and outlet temps of the evaporator. After the orifice tube (cold side) and the outlet (before the accumulator). Record and post info. These two temps should be the same....exact...or within 3-5 degrees of each other. The outlet temp indicates the actual evap core temp within a few degrees and this can be compared to actual vent temps to determine system operations.


Liquid side of orifice tube is 109* gas side is 68*
Evap inlet is 61 and evap outlet is 64
All measured with infrared.

Measure the condenser inlet and outlet temps as close to the inlet as possible. Post info.
Inlet 99
Outlet 88




Measure the temp drop across the orifice tube. Post info.
See above


Measure the center vent temperature and the temperature (ambient) approximately 12 inches in front of the condenser.
45* Vent with regular probe thermometer.
86* ambient


If possible post pressures...but temps will work as well.
29/175


Once this info is collected....repeat with the engine at 1500 PRM/MAX COOL/DOORS CLOSED/LOW OR SECOND BLOWER SPEED.
Can't run this test as the compressor will cycle constantly.


Let's see the info furnished by these components.




I very much appreciate your help. I'm hoping we can get this nailed.
This is not an insurmountable event. We simply need to establish a time line for repairs....and operational conditions. Certain events must occur for a AC system to perform....we just need to determine the location of the 'glitch'.

ascalise on Thu July 25, 2013 12:12 AM User is offline

It turns out I do have a thermocouple in my multimeter set.

Temps are as follows right now. I shut the truck off earlier and started back up 3 minutes ago and checked temps.

Evap inlet 47
Evap outlet 48

Gas side orifice tube temp 48
Liquid side 116


pressures right this second
35/200

ac on on recirc doors closed cabin temp 47* ambient 85*

ascalise on Thu July 25, 2013 12:17 AM User is offline

While we are at it the lines on the compressor are
61* low
135* high

Condenser in 134*
condenser out 115*
All measured with thermocouple until temps stabilized. Hope this helps

Pressures 30/190

Dougflas on Thu July 25, 2013 7:38 AM User is offline

Condenser appears to be doing its job. 20* drop in temp across it. Problem appears to be at orfice tube. You need lower temps at evaporator. I like to see mis 30's here. So let's think about it. Could some refrigerant be leaking by orfice? Wrong sized orfice tube? DEFECTIVE orfice tube with opening out of tolerance?

Remember, the evap's refrigerant will pick up heat from the air moving across it. If the temp of the evap is 47 or 48, The air going thru it can not be less than that amount.

I am suspecting a problem here. I do not have access to service bulletins but by any chance, was there a production change to the size of the orfice tube?

ascalise on Thu July 25, 2013 11:32 AM User is offline

There are no leaks. Orifice tube is fine. There is an updated design but requires a different line as the diameter is much larger.

iceman2555 on Thu July 25, 2013 3:31 PM User is offlineView users profile

Damnit....hate when I touch the wrong key and delete my post.

First, the statement about the tech and his recovery process indicating a 1 oz over charge. It is highly doubtful that this 'over charge' would be indicated by a modern recovery machine....secondly, 1 oz will not effect the operation of the system (at least this system) adversely.

The orifice tube used in this vehicle should be the 'black' unit...correct? GM has a replacement unit...it is a yellow/gold unit. It was originally produced for Caddy's and was to aid in low rpm cooling issues. It has a slightly smaller orifice and should increase cooling efficiency a bit. Not drastically but a bit. GM also has another orifice tube use on some models...do not recall it being utilized on this vehicle...it is larger..much large diameter and has a material similar to 'glass beads' on the tip. These beads are both the filter and the orifice itself. It does require a different hose to accommodate the extra diameter.

Back to your vehicle. Were these temperatures taken with the vehicle is a high heat load...MAX AIR...HIGH BLOWER....CABIN DOORS OPEN....IDLE SPEED....if so, then the system appears to be working. Although the pressures could be a bit low for an ambient temp of 85 degrees...esp with the doors open. What part of the US are you located....humidity concerns. If in the post...sorry missed it.

The posted temp drop for the condenser should be considered a bare minimum. This is typically a starting point for OE development. At this point, they would adjust charge levels...increase cooling/air flow...to arrive at a acceptable point. Normally on this vehicle...considering the size of the condenser, air flow restriction etc.....a temp drop more in the mid to high 20's would be more in line. I drive a 06 Sierra, 5.3 with the Denso compressor, OE condenser....dual electric fans and this unit generally stay in the 26-29 degree drop.

Is this vehicle equipped with a fan clutch or electric fans. Consider the age....could the vehicle need a new fan clutch. If electric fans...insure that the fans are truly operational

From the posted temps....and awaiting confirmation of operational test conditions, the system appears to be functioning. Ambient temp of 85 a vent of 47 equals a drop of 38 degrees. This should be considered a valid temp drop. However, this also goes back to the operational temp test conditions. This factor can change procedures drastically.

The temp drop across the orifice tube is normal....consider 65-75 degrees. The discharge temps/pressures are normal. And do not present a serious concern.

Compare the evap outlet temp to vent temps. The evap core is essentially 47=48 degrees...normal heat gain would be 5-7 degrees. This would equal a vent temp of 54-55 degrees.

Once more...dependent upon test conditions....all hinges on the conditions.. and charge rates.....if the condenser drop could be increase....this would increase cooing (vent temps) drastically. Drop the orifice liquid outlet temps and the evap will be cooler and the vent temps will be cooler.

If these test were made with the doors open....once the cabin is closed....and begins to cool...the vent temps should drop drastically. Consider that the inlet air temp to vent temp drop is 38 degrees....once the cabin temp drops to....say.....75 degrees.....75-38 = 37 degrees. This would be a cold vent temp.

One other issue....encountered this last summer. 2006 Chevy 1500...a very similar condition...except this unit would not cool as well....after a bit of testing we determined that the 'recir' door was not closing completely. It would move with the motor...could hear what appeared to be the sound of closing, but then door stayed open a few degrees.....and of course, this allowed for heat contamination to enter into the cool chamber of the system.

Let us know about the test conditions....it is important....however, it appears your system is functioning....perhaps a bit of 'tweaking'....but it is working.



-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson



Edited: Thu July 25, 2013 at 3:43 PM by iceman2555

ascalise on Thu July 25, 2013 5:00 PM User is offline

Quote
Originally posted by: iceman2555
Damnit....hate when I touch the wrong key and delete my post.



First, the statement about the tech and his recovery process indicating a 1 oz over charge. It is highly doubtful that this 'over charge' would be indicated by a modern recovery machine....secondly, 1 oz will not effect the operation of the system (at least this system) adversely.

I figured it wouldn't have made any difference.



The orifice tube used in this vehicle should be the 'black' unit...correct?
Correct Black and white

GM has a replacement unit...it is a yellow/gold unit. It was originally produced for Caddy's and was to aid in low rpm cooling issues. It has a slightly smaller orifice and should increase cooling efficiency a bit. Not drastically but a bit.
The ones i've been buying are the latest part for my truck by vin at the dealer.

GM also has another orifice tube use on some models...do not recall it being utilized on this vehicle...it is larger..much large diameter and has a material similar to 'glass beads' on the tip. These beads are both the filter and the orifice itself. It does require a different hose to accommodate the extra diameter.

Yes I have seen these, this is the "2nd design" that shows up everywhere in parts catalogs but will not fit my line.

Back to your vehicle. Were these temperatures taken with the vehicle is a high heat load...MAX AIR...HIGH BLOWER....CABIN DOORS OPEN....IDLE SPEED....if so, then the system appears to be working. Although the pressures could be a bit low for an ambient temp of 85 degrees...esp with the doors open. What part of the US are you located....humidity concerns. If in the post...sorry missed it.

They were taken with max air high blower doors CLOSED at idle speed. With doors open temps won't get anywhere near where they were. I am located in McAllen, TX. Southernmost tip of texas. It was 86* last night all night and about 75% humidity.



The posted temp drop for the condenser should be considered a bare minimum. This is typically a starting point for OE development. At this point, they would adjust charge levels...increase cooling/air flow...to arrive at a acceptable point. Normally on this vehicle...considering the size of the condenser, air flow restriction etc.....a temp drop more in the mid to high 20's would be more in line. I drive a 06 Sierra, 5.3 with the Denso compressor, OE condenser....dual electric fans and this unit generally stay in the 26-29 degree drop.



Is this vehicle equipped with a fan clutch or electric fans. Consider the age....could the vehicle need a new fan clutch. If electric fans...insure that the fans are truly operational

The diesels have a giant fan blade with a fan clutch which is working properly.


From the posted temps....and awaiting confirmation of operational test conditions, the system appears to be functioning. Ambient temp of 85 a vent of 47 equals a drop of 38 degrees. This should be considered a valid temp drop. However, this also goes back to the operational temp test conditions. This factor can change procedures drastically.

I agree that 47* is a reasonable temp but like i said it takes entirely too long to get there. Even last night at 86* it took forever. During the day temps wont get below 55* And again, all it takes is a touch of the go pedal and the compressor cycles constantly. Temp will go up 5-7 degrees within 1 minute sitting still or driving down the road.



The temp drop across the orifice tube is normal....consider 65-75 degrees. The discharge temps/pressures are normal. And do not present a serious concern.



Compare the evap outlet temp to vent temps. The evap core is essentially 47=48 degrees...normal heat gain would be 5-7 degrees. This would equal a vent temp of 54-55 degrees.



Once more...dependent upon test conditions....all hinges on the conditions.. and charge rates.....if the condenser drop could be increase....this would increase cooing (vent temps) drastically. Drop the orifice liquid outlet temps and the evap will be cooler and the vent temps will be cooler.



If these test were made with the doors open....once the cabin is closed....and begins to cool...the vent temps should drop drastically. Consider that the inlet air temp to vent temp drop is 38 degrees....once the cabin temp drops to....say.....75 degrees.....75-38 = 37 degrees. This would be a cold vent temp.

This system up until 2 months ago could cool to 39-40* in the heat of the day and would not take long to get there.



One other issue....encountered this last summer. 2006 Chevy 1500...a very similar condition...except this unit would not cool as well....after a bit of testing we determined that the 'recir' door was not closing completely. It would move with the motor...could hear what appeared to be the sound of closing, but then door stayed open a few degrees.....and of course, this allowed for heat contamination to enter into the cool chamber of the system.

When i had the box out of the truck i looked at this. At the very end of the range (recirc door) closed there are standoffs on the frame that hold it open about 1/4" The recirc does operate as it should. To verify this I covered up the top of that with a plastic bag with no change.



Let us know about the test conditions....it is important....however, it appears your system is functioning....perhaps a bit of 'tweaking'....but it is working.

Cycling is my biggest concern right now. I can not get the compressor to run long enough to take the heat out of the cab unless it is idling. With the proper charge and measured temps and pressures it should not be cycling as soon/often as it is. This reminds me, I failed to mention in the first post that the low pressure switch has been replaced with every drier and even one from the auto parts store just to rule that out. I also replaced the pigtail going to the low pressure switch.

iceman2555 on Thu July 25, 2013 5:31 PM User is offlineView users profile

The question has been asked....how was the system tested....max heat load...or minimal load (doors closed). This makes a vast difference with temp testing.

Cycling rapid is typically the result of LPCO....typical of a undercharged system....HPCO ...typical of a restriction in the discharge side or a possible over heating condition.

The system should not cycle due to low pressure issues if the system is under high heat loads...doors open.

Disconnect the LPCO switch to determine if this is the root cause....if the cycling stops...check the HPCO switch.

Also, is this not an Automatic AC Climate system....if so...try these test with the system in manual mode. See if the conditions repeat.

How was the system recharged....it is know that at one time it was in a shop....is this still being done...or is an attempted being made to charge the system by hand. One of the post indicated that the charge rate was increased to enhance cooling efficiency.....this charge rate is critical and should be accomplished with a charge machine or a weighted scale. Another unanswered question is the age of the recovery machine, if one is being used. Older machines....tend to be less accurate...due to age and lack of maintenance.

We have moved from a mechanical problem to a control problem.

For the temperature test to be determined accurate...need to know the system test conditions.



-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

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