Automotive Air Conditioning Information Forum (Archives)

Provided by www.ACkits.com

We've updated our forums!
Click here to visit the new forum

Archive Home

Search Auto AC Forum Archives

All new A/C in Suburban- mediocre performance

alfamike on Sat September 04, 2010 9:16 PM User is offlineView users profile

Year: 1995
Make: Chevy
Model: Suburban
Engine Size: 6.5
Refrigerant Type: R134a
Ambient Temp: 95
Pressure Low: 52
Pressure High: 305
Country of Origin: United States

This is a dual A/C & heat Suburban, & being a 95 model 6.5 turbo diesel, it uses an R4 compressor. I installed new compressor (4 Seasons), OT (black), accumulator, & rear expansion valve. I flushed the entire system, pulled vacuum for about an hour, & recharged with 4 lbs of refrigerant & 11 oz of PAG.

It also has had new radiator, t-stat, hoses, & fan clutch in the past 2 years. The areas in front of the radiator & in front of the condenser are both perfectly clean. In fact, I had to replace the condenser (& liquid line & hoses & evap) when I did an A/C job in this vehicle about 5 years back due to stripped threads by the PO's mechanic. The brand new AC Delco compressor I installed 5 years back failed, which necessitated doing the A/C again. I replaced the fan clutch again today because the car was running a little too hot in heavy traffic. It doesn't overheat any more when idling for a long time, & I can now hear the fan clutch working when I drive after letting it idle for a long time.

Despite all this, vent temps at hot idle (650 rpm) are 62 in the front & 68 at the rear A/C vents. In city driving, I get 53 degrees from the front vents, & it drops down to 47 on the freeway.

Recirculating mode seems to be working properly. I can hear the change when I take it out of recir. mode, & the vent temps climb. Temps come back down when I put it back to recir. mode. Also, the blend door seems to be functioning properly. Moving the temp control knob to about the 1/2 way point causes vent temps to climb, & they come back down when I put it back to full cold. I checked the rear blend door while replacing the rear expansion valve, & it works properly as well.

I'm all out of ideas. I think the only other possibilities are that I don't have the correct charge level (I only have the 12 oz cans & no scales), or my new rear expansion valve is not performing optimally. It was a run-of-the-mill aftermarket unit. Is there anything I can do to test either of these possibilities and/or is there something else I've overlooked? A search of the extensive archives on Suburban A/C issues didn't yield any new info.

Thanks in advance for any input.

-------------------------
Michael Keith
Houston, TX

Edited: Sat September 04, 2010 at 9:30 PM by alfamike

iceman2555 on Sat September 04, 2010 9:43 PM User is offlineView users profile

First and foremost, the charge of the system should be known. Fortunately for these system there is a good method to help. Obtain some method to test surface temperatures of metal. An infra red or laser are ok...but prefer a touch thermocouple. Several companies supply this and cost can be reasonable to something that only stimulus money would cover. Sears sells a good DVM with a thermocouple for less than $50.00. Check other sources, perhaps, site sponsor can supply a unit.
Operate the vehicle for app 10 minutes with both systems operational. Test conditions, Max Air (recirculate), High blower, Doors open, engine @ idle speed. After the time period, decrease fan speed to the rear unit or if possible shut it down. Allow system to operate for another 3-5 minutes. Measure the inlet and outlet temps of the evap core. These temps should be the same or within 3-5 degrees of each other. Ideally the same. If the outlet is warmer than the inlet by more than 6 -8 degrees, the system is slightly undercharged. If preferred add app 2 oz of refrigerant to the system. Allow system to operate app 5 minutes and retest temps.
If the inlet is warmer than the outlet by more than 6-8 degrees,the system is slightly over charged. Being able to charge by weight is far more acceptable than adding a bit here and there....or subtracting a bit here or there.
Once the system is properly charged, measure the inlet and outlet temps of the condenser. An acceptable temp drop of 25-30 degrees. If over 35-40 degrees there is a good possibility of a restriction in the condenser. Since the current condenser has suffered one compressor failure, this is a good possibility.
Also was the fan clutch used a OE replacement or someone's 'heavy duty' model. If possible post part number and location of purchase...we can do a bit of background checking on this very important part.
The heat index in Houston was almost 100 today....at this point, the temps are not too far out of spec. However, it never hurts to check. Depending upon your charge procedure, it is quite possible your system is undercharged 4-6 oz.
Good luck!

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

alfamike on Sat September 04, 2010 11:03 PM User is offlineView users profile

Thanks for the suggestions. I was wondering if I might be expecting too much, but before the other system went belly-up, I'm pretty sure it performed better under similar condition. It was capable of keeping the wife happy/quiet. :-)

I'll have to go with a laser/infrared unit to measure line temps as access to the front evap outlet on the 6.5 diesel Suburbans is very difficult. I've been wanting to get one of those anyway. Here's my excuse. Better yet, it sounds like I ought to bone up & pay someone with the proper equipment to recover/recharge the system. Any recommendations for someone in the Houston area, especially southeast side/Pasadena (home) or Midtown area (work), would be appreciated. As long as I don't have to change that rear expansion valve again, I'll be happy.

Although there was some trash in the OT as well as the rear exp valve inlet, the system flushed out quite easily, & I flushed the condenser twice to be sure.

As for the fan clutch, both the one that was on the vehicle as well as the new one I installed today were Haydens (part #2831) purchased from Shaver Auto Parts; a small parts house in Pasadena that I've done business with for about 15 years.

-------------------------
Michael Keith
Houston, TX

iceman2555 on Sun September 05, 2010 2:38 PM User is offlineView users profile

The Hayden fan clutch is the correct number for your series.
The issue with little debris located in the orifice does not indicate that the condenser is not restricted, nor the fact that it flushed clean. The blow thur method is simply not sufficient to clean most of the late model condensers. Temp testing will indicate more.
Good luck with your repair!

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

bohica2xo on Sun September 05, 2010 4:32 PM User is offline

That vehicle has a serpentine condensor. Given that the condensor is the primary filter, and both secondary filters had compressor debris - I would have thrown it straight in the trash.

You can block 30% of a serpentine condensor, and never spot it blowing air through it.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

alfamike on Sun September 05, 2010 5:44 PM User is offlineView users profile

As much as I dislike the idea of replacing the condenser....AGAIN, that does make a lot of sense. The A/C performance is similar to that of a vehicle with an faulty fan clutch despite the fact that the fan clutch does indeed work properly.

-------------------------
Michael Keith
Houston, TX

bohica2xo on Sun September 05, 2010 7:11 PM User is offline

I know, it sounds bad. The reality is that R4's grenade, and that part is the filter.

I try not to think of it as a condensor anymore. It is just a 118 dollar filter with a 5 year service life. You probably spend more than 23 bucks a year on filters anyway. Some newer cars cabin air filters are 50 bucks now...

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

alfamike on Sun September 05, 2010 9:50 PM User is offlineView users profile

I guess it's not too bad. I'm just ticked that I didn't think about it that way when I had the system apart, especially since I've replaced that condenser before, & I know what it looks like. I work on old Italian cars for a living; so I guess I'm just more accustomed to the old tube & fin condensers.

Since the vehicle is in use, & probably will be until I have time to tackle this, will remaining debris escape out of the condenser? IOW, should I again replace the OT & the rear exp valve?

-------------------------
Michael Keith
Houston, TX

iceman2555 on Mon September 06, 2010 10:37 AM User is offlineView users profile

The problem with operation of this system with a possible restriction,is the reduction of lubricant flow thru the system. This will lead to a repeat compressor failure. Lubricant starvation is a major contributor to compressor failures.
Yes, there is a good possibility that the 'debris' will migrate to the orifice tube and possibly the rear TXV. As this material migrates to the OT, the filter screen of the OT will become restricted and thus this may be come an additional restriction.
Suggest to repair the system ASAP and not simply 'put it off', or simply stop using the system until such time as the repair can be accomplished.

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

Dave in Texas on Mon September 06, 2010 3:43 PM User is offlineView users profile

I don't have near the professional experience that the guys who answered possess, but enough to heed what they say. Turn if Off and use the old-time 2-60 cooling method until you can fix the system once and for all. Cold weather is a mere 5mths away after all....

-------------------------
At 2, I went home with a 10. At 10 I woke up with a 2 !!

Edited: Mon September 06, 2010 at 3:45 PM by Dave in Texas

alfamike on Mon September 13, 2010 12:49 AM User is offlineView users profile

I bought a laser/infrared temp gun with a thermocouple. Unfortunately, due to accessibility issues, I was not able to use the thermocouple, & as a result, my readings were inconclusive. After running the system as iceman2555 instructed, my evap inlet showed 97F, & the outlet was all over the place but seemed to read 82 more often than not. This would seem to indicate a grossly overcharged system, but I know that's not the case. As for the condenser, the inlet was 147 & the outlet was 138. The inlet & outlet were right next to each other with both only accessible through a narrow opening from about 18" to 24" away. Therefore, I doubt these readings are valid.

However, I discovered a couple of things. First off, my new compressor has developed a front seal leak. Therefore, I will have to replace it again. Because of that, & because of the possibility of problems with my condenser, I'm going to suck it up, & replace the condenser as well.

Also, throughout this exercise, I had my gauges on the car, & I discovered that system pressures changed significantly when the rear A/C was turned off. With the rear A/C off, my high side was 235, & my low side was 30. With the rear A/C on, my pressures were about the same as what I originally posted (305/52). This was another 95F Houston summer day. Does this indicate some sort of problem with the rear expansion valve? I have to admit that I've never actually checked system pressures with the rear A/C off; so I don't know what is normal here. Any time I've had gauges on this system, both systems have been running full blast. I did install a new rear expansion valve when I replaced the rest of the system, but it was a run-of-the-mill aftermarket unit.

-------------------------
Michael Keith
Houston, TX

Cussboy on Tue September 14, 2010 2:46 PM User is offline

I'm in Arizona, just sold the '94 Suburban I had for 10 years. It is factory R134a, and also had the R4 compressor (mine was gasoline engine though). My AC worked very well here, although I did need to replace the compressor every three years due to belly leaks. In 2009 the rear AC stopped blowing cold, assumed the rear expansion valve was either clogged or stuck closed. However, my kids were now away at college, rarely had passengers in second or third seats. Early 2010 I again replaced the compressor (another belly leak) with new Delphi R4, also replaced accumulator (it had sat for 5 months without refrigerant), added the full 64 oz. R134a, and 8 oz. of PAG oil (the old compressor was devoid of oil). The AC worked great, you don't need the rear AC operable, or on, to have nice front AC performance.

alfamike on Tue September 14, 2010 11:46 PM User is offlineView users profile

I have two kids; so I need the rear A/C. However, the rear A/C works. It's just 6 to 8 degrees warmer at the vents than the front. My question was more related to the pressure drop in the system when the rear A/C is turned off. I've never checked system pressure with the rear A/C off; so I don't know if that's normal. Since I'll have to open up the system again anyway, I'd rather know now if I got a defective rear expansion valve.

-------------------------
Michael Keith
Houston, TX

alfamike on Sun October 17, 2010 11:58 PM User is offlineView users profile

I have an update on this, & it's not good. I ended up re-doing the entire job, including a new p-flow condenser, & I ended up with just about same results: 60 from the front vents & 66 out of the rear vents. Front vent temps drop to 50 when driving on the freeway. This with ambient temp at 83F & 47% humidity. Pressures were 260 & 48. In fact, given the fact that ambient temps were about 10 to 15 degrees higher the 1st time I did this job, you could argue that the results are worse for this second go-round.

As I mentioned before, I had to replace the compressor again anyway because the new one started leaking from the front seal, & I also got a new condenser (p-flow). I found the OT to be clogged with shavings; so that confirmed the opinions expressed here that the original condenser still had blockage. Therefore, in addition to a new OT, I opted for yet another new accumulator & rear expansion valve.

I flushed the rest of the system & collected what was flushed out into an old gallon bottle of drinking water. I flushed each part of the system (that was not being replaced) repeatedly until nothing but clean flush solution appeared in the bottle. I went through about a gallon of flush solution.

I added 11 oz of oil: 2 in the compressor; 1 in the condenser; 3 in the evap; 3 in the accumulator; 2 in the rear evap. I pulled vacuum for an hour, let it sit overnight, & it held just fine. I pulled vacuum for another 15 minutes this afternoon before charging with exactly 64 oz of refrigerant. I monitored vent temps the entire time I was charging the system, & nothing strange happened except that it just wouldn't pull down below 60.

The accumulator sweats quite a bit, as does the low side line for the front A/C all the way back to the compressor. However, there is very little water out of the front evap drain. OTOH, the low side line for the rear A/C doesn't sweat at all & doesn't even feel cool to the touch. No water drains from the rear evap. All of this leads me to believe that perhaps the rear EV is the culprit. However, the rear is only blowing 6 degrees warmer than the front. Also, this difference between front & rear was present the 1st time I did this job. What are the odds of getting two defective rear EV's?

Any suggestions before I set this thing on fire!?

-------------------------
Michael Keith
Houston, TX

HECAT on Mon October 18, 2010 10:09 AM User is offline

Quote
Originally posted by: alfamike
As I mentioned before, I had to replace the compressor again anyway because the new one started leaking from the front seal, & I also got a new condenser (p-flow). I found the OT to be clogged with shavings; so that confirmed the opinions expressed here that the original condenser still had blockage. Therefore, in addition to a new OT, I opted for yet another new accumulator & rear expansion valve.

I flushed the rest of the system & collected what was flushed out into an old gallon bottle of drinking water. I flushed each part of the system (that was not being replaced) repeatedly until nothing but clean flush solution appeared in the bottle. I went through about a gallon of flush solution.

1 gallon for 2 evaps and long rear lines. I would consider that three separate flush jobs at 1-2 gallons each. How did you flush, how did you remove all the solvent, how did you test for cleanliness? It appears there is evidence the first flush job/work was insufficient; what did you do to improve the process with the next attempt? Just wondering if residual cleaner has anything to do with the poor performance.


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


HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 


Edited: Wed October 20, 2010 at 2:30 PM by HECAT

TRB on Mon October 18, 2010 10:57 AM User is offlineView users profile

For me using the term PF condenser is too generic these days. Need to see a pic of the condenser being used to determine what improvement it may or may not have had on the system.

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

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

knightgang on Wed October 20, 2010 2:11 PM User is offline

This might seem a dumb question, but have you confirmed that the drains on the evap boxes are clear. You mention that the Lines and Accumulator are sweating quite a bit. I suspect that you evaporators are as well, yet you say very little water is drianing. If the drains are clogged, then the evaps are sitting in water and will affect performance. I have this happen to me on a previous car. Once the drain was cleared and the water escaped, the temps dropped like a rock and was pulling 35-38 deg vent temps in about the same ambient.

alfamike on Sat October 30, 2010 10:24 AM User is offlineView users profile

Thanks for all the input everyone. Sorry it's taken so long to get back to this thread. Due to some far more pressing family issues, this will have to go on the back-burner for now.

HECAT, I had a chance to read over your flushing material, & it was very informative. I don't have time to go into all the details of how I went about flushing the system, but I'll give the broad strokes. I used the typical flush gun that you fill with solvent & attach to your air compressor. I collected the output in a clean container, & on each component, I did a series of small flushes rather than one big flush. I did this repeatedly on each component, cleaning my container after each flush, until I collected nothing buy clean solvent. This usually took 3 flushes per component. From there, it was about 1 to 2 minutes of plain air shot through each component. I didn't flush through any filters, mufflers, OT's or expansion valves.

I hope you're wrong about your conclusions, but you maybe right. I did this job a second time based on an earlier suggestion in this thread that I did not get all the debris out of the original condenser. That person was absolutely correct. When I pulled the OT, it was covered in debris after only a couple of months of operation. It could be that there is also debris in both evaps that my equipment is not capable of removing.

TRB, I did get a true PF condenser. This photo http://www.ackits.com/merchant.mvc?Screen=PROD&Store_Code=01&Product_Code=24-50019&Category_Code=Parallel is not of the exact condenser that I purchased, but it's an accurate representation. In any event, PF vs non PF is not central to the problem. I only replaced the original condenser due to debris that could not be flushed out. The PF unit is all that my A/C supplier offers.

knightgang, Yes, both evap drains are clean & clear. Both evaps do drain, just not as much as they're supposed to.

Once I have a chance to evacuate the system & remove the OT, I'll find out if HECAT's prophecy of doom is correct. If it is, I'll be looking for someone in the Houston area who has top flight flushing equipment.

-------------------------
Michael Keith
Houston, TX

HECAT on Sun October 31, 2010 5:55 AM User is offline

Quote
Originally posted by: alfamike
HECAT, I had a chance to read over your flushing material, & it was very informative. I don't have time to go into all the details of how I went about flushing the system, but I'll give the broad strokes. I used the typical flush gun that you fill with solvent & attach to your air compressor. I collected the output in a clean container, & on each component, I did a series of small flushes rather than one big flush. I did this repeatedly on each component, cleaning my container after each flush, until I collected nothing buy clean solvent. This usually took 3 flushes per component. From there, it was about 1 to 2 minutes of plain air shot through each component. I didn't flush through any filters, mufflers, OT's or expansion valves.

I hope you're wrong about your conclusions, but you maybe right. I did this job a second time based on an earlier suggestion in this thread that I did not get all the debris out of the original condenser. That person was absolutely correct. When I pulled the OT, it was covered in debris after only a couple of months of operation. It could be that there is also debris in both evaps that my equipment is not capable of removing.

Once I have a chance to evacuate the system & remove the OT, I'll find out if HECAT's prophecy of doom is correct. If it is, I'll be looking for someone in the Houston area who has top flight flushing equipment.

Thanks for reading the flushing information provided; I am glad you found it informative. It appears from your description that you were very diligent in your efforts to flush with the typical flush gun. However, I do have a concern that this particular tool lacks the physical ability to produce the necessary solvent volume and velocity to be effective on a highly contaminated system. Secondly, I don't know what chemical you were using, but for most commercial A/C cleaning solvents, the 1 to 2 minute plain air shot is no where near enough time to properly dry out (evaporate) the component.

I do hope I am wrong with the prophecy of doom.




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


HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 


Edited: Sun October 31, 2010 at 5:56 AM by HECAT

Back to Automotive Air Conditioning Forum

We've updated our forums!
Click here to visit the new forum

Archive Home

Copyright © 2016 Arizona Mobile Air Inc.