Automotive Air Conditioning Information Forum (Archives)

lesrwoody on Sat August 07, 2010 12:58 PM

Year: 2004
Make: chevy
Model: avalanche
Engine Size: 5.3
Refrigerant Type: 134
Ambient Temp: 90
Pressure Low: 55
Pressure High: 300
Country of Origin: United States

still haveing problems with ac. ok i know my sys is low but thats the only way i can get it to cool,not cold just cool with fan on high.turn fan to low speed and yes it will get cold but at a little over 2000 rpms the low press switch kicks out the compressor. like i said i know its low but i want to knoe why the low side press wnot come down when the engine is started? i know low side should read about 40 psi @1500 rpm so why is the low side staying high all the time?even when i start the engine?

TRB on Sat August 07, 2010 1:16 PM

Too much oil or a air flow across the condenser could cause this issue. Plugged passages in the condenser would also cause this. Need more information on what has been done to help further.

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When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

lesrwoody on Sat August 07, 2010 1:24 PM

started to noitce that it wasnt cooling well,took sys down replace orfis tube,white was in they gave me a black one,vac and charge sys with good vac pump.still wouldnt cool.

iceman2555 on Sat August 07, 2010 1:28 PM

If the posted pressures are relative to an undercharged system....there may be a serious issue with your vehicle.
This vehicle measures high side liquid pressures and low side liquid (vapor) pressures. It is highly doubtful that the low side on this vehicle will indicate a low side pressure in YOUR desired area. One must forget the idea of an ideal pressure....the system should be charged correct and all engine cooling system components working properly.....the resultant pressures will simply be the operational pressures of that particular system.
Operation of an undercharged system will result in a complete compressor failure and on this vehicle....this may mean a total system failure. There are several characteristics of this system that may make repairs quite expensive.
A suggestion would be to have the system serviced....properly recharged utilizing the correct equipment and then post the resultant pressures. Considering the location of the low side service port on this vehicle....the expectations of a low pressure that meets you demands is almost impossible, given your ambient temperature range....and not knowing the heat index of your location. One must understand the operation of the system....the state of refrigerant at any given point in the system and the location of the service ports.
Do not maintain operation of this vehicle in a seriously undercharged mode....the benefit out weights the consequences.


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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

lesrwoody on Sat August 07, 2010 1:45 PM

i don't want to operate my truck in this state i want to figure out the problem,i don't drive this truck very often maybe one time on the weekend. im in lagrange georgia and yes its hot here i understand that, i was just thinking that low reading should get down to about 40psi at 1500 rpms. if it stays around 55,60 its not cooling very well. im just seeking some info thanks. oh also when my sys is full charged i get a rattle from under the hood when i accelerate

Edited: Sat August 07, 2010 at 1:57 PM by lesrwoody

mk378 on Sat August 07, 2010 4:01 PM

The problem starts from the high side being too high. The compressor is really straining to pump against all that pressure, so it can't bring down the low side. Like the others said, consider poor condenser airflow, too much oil, or blockage in the condenser.

lesrwoody on Sat August 07, 2010 6:51 PM

thank you all for the answers you all have been a big help!i pulled out the orfis filter and found some little rubber chips i will try blowing the condensor out with shop air.

chris142 on Sat August 07, 2010 7:53 PM

That wont do a thing. You either need to replace it with a new one or use Hecats flusher on it.

TRB on Sat August 07, 2010 8:04 PM

Debris in the orifice tube could mean blocked passages in the condenser and a compressor issue. To truly determine what is going on you will need to pull the accumulator. Drill a hole in the bottom and capture that oil . Then cut the accumulator in half using a hacksaw. Only cut the canister do not cut all the way through it. You need to inspect the desiccant bag.

-------------------------

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

iceman2555 on Sun August 08, 2010 1:13 AM

Dang it...hate when I hit the wrong key and erase all.

Not sure what vent temps are expected from this vehicle. Consider that the heat index in LaGrange, GA today was about 140. (97 and humidity of 94%). This is a serious heat load.
The posted pressures.....300 psi is not far out of range...considering the temp and rpm. Not sure why one would wish to operate at 2000 rpm...considering the vehicle....this would equate to an operational speed of app 70 mph. It is highly doubtful that the fan clutch can mimic the air flow experienced at this speed.
Why not try a heavy heat load test...max air...high blower....doors open...engine at idle....allow the system to operate for 5-10 minutes...then measure the inlet and outlet temps of the evap...should be equal....3-5 degrees variance.... Test the condenser inlet and outlet temps....should see a drop....25-28--30 degrees.....excessive drop indicates a possible restriction.....low drop may be a charge issue or fan clutch operation. Considering the age of the vehicle...the fan clutch would be a prime candidate for replacement.....in conjunction with having the system professionally recharged. It is almost impossible to adequately recharge the vehicle using cans and attempting a perceived pressure.

Measure ambient temp....about a foot in front of the condenser....compare this temp to center vent of your vehicle....should see a drop....25-30 degrees. Post results.

The question concerning the high low pressure readings at start up can be contributed to the head load on the system when the evap is exposed to this excessive heat. The system should be allowed to operate for a few minutes and allow the evap to cool prior to conducting pressure/temp test. Considering the excessive heat load of this season...this could be several minutes.

We have seen an abundance of tech calls this year concerning issues similar to this concern. Keep in mind that this has been an exceptional summer...with many regions experiencing heat ranges that have not been experienced for years.

The first and foremost diagnosis procedure is to insure that the system is totally recharged....and unfortunately....charging with cans may often not be the most advantageous method to accomplish this. Have the system served by a professional who has the correct and updated equipment to accomplish this task.


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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

TRB on Sun August 08, 2010 1:20 AM

If you're writing that much info. Do it in a text editor and cut & paste my friend. Text editor is free with all OS software. So don't give me your corporate card is maxed out.

-------------------------

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

lesrwoody on Sun August 08, 2010 10:44 AM

to answer ice man 2555, i have changed the fan clutch, i do belive it has a possible restriction in the sys , due to the rubber found in the filter. do you guys think their is any way it made it into the evap? i hope not. like i said i do know it is hot in georgia and humid as i have lived here all my life,but i also know my ac is not working properly i also know heat affects pressure. vent temp is 65* i also know you guys know a lot more than i do but like i said its not working right,the ac in my other car is working good with a vent temp of about 53* so i can tell the deference . oh yea and my truck has a 4.10 gear so at 2000 rpm im runing bout 65 mph .

Edited: Sun August 08, 2010 at 11:02 AM by lesrwoody

iceman2555 on Sun August 08, 2010 2:31 PM

The best beginning is a proper recharge....then diagnosis the system.
Yes, it could be a restriction in the condenser...but that is easy to check.....once the system is properly recharged. Inlet and outlet temps tell a great deal.
The high side service port on this vehicle is located on the downstream flow of refrigerant from the compressor thru the condenser. The high side pressure normally at this point would not be as excessive as indicated....IF the condenser were restricted.

It can not be stressed enough that the system must be properly recharged to properly diagnosis a system performance issue

Your compressor is capable of pumping 300 psi....this normally indicates a functional compressor....esp when these pressures are on the liquid side. If we were measuring discharge pressures...then the excessive pressure could be the result of a restricted condenser. A restricted condenser, normally located in the inlet side) will result in an elevated discharge pressure. The restriction acts as an orifice and the result is a possible decrease in liquid line pressures. You liquid line pressure is high...not abnormally so for the rpm range and temperature.

The mph calculations were made considering a 3.73 gear set, which was standard for your vehicle that year. It makes no difference...the fan clutch can not produce that amount of air flow.
You stated the fan clutch had been changed....could I ask where your purchased your clutch and if possible supply the part number. Would like to do a bit of research. A new fan clutch could still be 'slipping' an excessive amount and the result would be a situation similar to yours.

However, all test must be made on a fully charged system....and from information supplied...this is not the case here.

Charging by cans is a 'hit and miss' for a seasoned tech and almost an impossibility for a DIYer. There have been several studies conducted utilizing this procedure....and all have shown that this procedure leaves a lot to be desired....it is a very difficult procedure to accomplish and accomplish correctly. 134a is so charge sensitive that 1 or 2 oz can make or break a system....longevity and performance. Operational pressures indicated in a service manual are precedence on the fact that a system is charged properly...these are not meant to be a gauge for how much refrigerant to add to a system until a perceived acceptable pressure is obtained.

We see it each day......a call from a tech that is having serious issues.....parts or performance.....and inevitably the shop does not have a recovery/recharge machine and 'hand' charges. Follow up with shops that seem to contribute the majority of returns reinforces this issue part installation problems.

It is understandable that your system is not performing to your expectations...but one must look at what those expectations are....the ability of the system to meat those expectations....and the first step is get the darn thing charged properly.

There were several test suggested in a previous post....try these....they work....and can assist in removing some of the questions concerning this system. There is not straight forward answer to a system performance issue similar to yours....there are steps to follow....and all lead to a conclusion.....it is up to you to accomplish these steps. We can supply answers....but the information needs to be based on solid evidence.

Yes, I know....the free program thing, TRB.....just laziness on my part !!!!

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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

lesrwoody on Sun August 08, 2010 4:36 PM

lets just say for the heck of it the sys is full charge,would the pressures be with in range?i got the fan from advanced auto,now i know some people must have oem parts but it had an oem part on it before i changed the fan clutch and it was doing the same thing. also the rubber peices in the filter mean nothing? i checked inlet and outlet of condenser with a lazer temp gun and found in temp i think was 126 out at the bottom was 99* but i did find a place that was 157 *i was thinking this may be a singe of a blockage? also it must be common for the high side to be 330 psi? i always was told the high side should never get over 250 psi ? if so their is a problem. i don't have much faith in local shops cuz the first thing they want to do is replace the compressor,then part after part.i can throw money at it just as well as them,cuz i will look for cheaper parts.not go to the dealer. think i will just redo the whole sys. compressor , condenser,drier. heck to get warranty i have to buy all this any way. oh i found the fan clutch part# 215152 advance auto, also the old one has a number on it to but dont know if this is a part mumber?3c3oe2? the new one is made by it says imperial automotive products. also let me state the 65 psi is at idel not 1500 rpm. and that is about the vent temp. i would think i should be able to see at least 55* at the vents. also the code in the glove box say g80 and gt5 witch indacates 410 gear set with locker.

Edited: Sun August 08, 2010 at 5:08 PM by lesrwoody

iceman2555 on Sun August 08, 2010 5:10 PM

The fan clutch is an old Imperial number. The clutch is now produced by Hayden. Hayden at one time was a independent company located in CA. Now it is owned by Four Seasons. The clutch is listed as a 'severe' duty unit. This is normally an upgrade from the 'original OE' unit. Personally trusted Hayden more when it was independent.
The issue with the condenser.....the temp range appears to be within specifications...except for the note concerning the 'hot 157' area. Measurements should not be taken at the 'top and bottom'...this does not follow the flow patter of this unit. Measure the temp of the line entering the condenser and the line that exits the condenser. This is the inlet and outlet.
But once more, this temperature is affected by the amount of refrigerant in the system.

The idea that a system must operate at no more than 250 psi is believed by many...however, it has no validity. Check this chart. It from an older tech manual but does indicate some pressure/temperature adjustments relative to humidity.

Since it is evident that you posses a temp measurement tool...why not check the inlet and outlet temps of the evap.....this will give an idea of the possible charge of the system. Refer to previous post for test conditions.

Comparing vent temps from one vehicle to another is not a valid test. There are various conditions between vehicles that may produce different vent temps. One must work with the vehicle at hand to produce the best possible operational conditions/pressures/temps.



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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: Sun August 08, 2010 at 5:24 PM by iceman2555

lesrwoody on Sun August 08, 2010 5:20 PM

yes i did that the line that comes in at topin and one at bottom . the hot sopt is about the 3rd and 4th flue down , and from the seam out about three inch out to the right of the left side of the condeser.i will go check again to make sure im telling u right

lesrwoody on Sun August 08, 2010 5:47 PM

the top line was 110 bottom 125, the hot spot was 155 and around that was 146 .the farther away from the spot the cooler it got. i think the engine heat was effecting my reading in the evap lines 100 on the big line 99 on the high side the small line. and the truck has been setting right out in the sun. also the truck seams to cool better at highway speeds not cold but kinda cool . it wont cool well at all at idel witch i know points to condenser,fan clutch . not enough air across,but thats why i changed the fan clutch. also kinda of a smell sometimes like i don't know ? u guys know that air conditioner smell. oh i got stale air smell.

Edited: Sun August 08, 2010 at 5:48 PM by lesrwoody

iceman2555 on Sun August 08, 2010 5:50 PM

Measure at the specified locations. Your condenser may be a bit different from this model. I think yours is a Parallel Flow Hi Eff model. However, the location of the excessive temperature is near the first diverter in the condenser.

The evap inlet and outlet test important. Be sure to not allow excessive engine temperature to contaminate your recordings.

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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

lesrwoody on Sun August 08, 2010 6:31 PM

top 110 bottom 125

lesrwoody on Sun August 08, 2010 6:35 PM

Quote
Originally posted by: lesrwoody
the top line was 117bottom 125, the hot spot was 145 and around that was 137.the farther away from the spot the cooler it got. i think the engine heat was effecting my reading in the evap lines 100 on the big line 99 on the high side the small line. and the truck has been setting right out in the sun. also the truck seams to cool better at highway speeds not cold but kinda cool . it wont cool well at all at idel witch i know points to condenser,fan clutch . not enough air across,but thats why i changed the fan clutch. also kinda of a smell sometimes like i don't know ? u guys know that air conditioner smell. oh i got stale air smell.



Edited: Sun August 08, 2010 at 6:57 PM by lesrwoody

lesrwoody on Sun August 08, 2010 7:18 PM

also a few days ago i hooked up my low press gauge to the other car and just as i was thinking it should , as soon as i started the engine the low side went to 35 psi. why will this sys do that but my other wont? i also charged a truck a few years back and did the same thing,low side at 40 psi and it worked great. lot better than this neither air in this truck has not really worked well since i got it a year ago but in this type of heat it really shows am a member of the avalanche forum and their are lots of post with guys not happy with the performance of the ac sys. i have checked the blend doors crimped off heater hoes and still don't know whats wrong.just for kicks you should go to this form and check out some of the post on these problems.they say these trucks or sys in these trucks are bad about not cooling when stopped at a light or in traffic. hey how bout i just bring it to you and you troubleshoot it i see your georgia bull dogs pic,go dogs sick em hahaha thanks for all your answers man ! im not doubting you at all just getting info

iceman2555 on Mon August 09, 2010 12:33 AM

Not a fan of infra-red or laser temp units....possibility of excessive much heat contamination. Prefer a true touch probe.

If the posted temps are accurate...there is a serious condensing issue. This issue must be addressed...however, the validity of all temp measurements go back to the fact that the system must be fully charged. We can banner back and forth for hours on end....but this is simply useless......the system must be fully charged and charged with equipment that will allow you to know that it is properly charged. Get this done and post pressures and temps....at that point we can discuss what issues your vehicle has....no 'lets say for the heck of it' scenarios....get it charged correctly.

My POV is a 06 Sierra and it cools great. There is no reason for this system not to cool your vehicle.



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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

lesrwoody on Mon August 09, 2010 6:30 AM

What about the rubber in the filter? Where did it come from ? Compressor? Also when the did is in a low state and compressor cycles out it does this at 40 .si on low side,it never goes below that. Is that strange.I was thing it should bottom our at the time it cycles off?

Edited: Mon August 09, 2010 at 7:17 AM by lesrwoody

mk378 on Mon August 09, 2010 8:29 AM

Need to measure both pressures with accurate gauges to see what is going on. It could be cycling on the high side pressure.