03 Suburban AC Issues - Diagnostic Challenge for Intermittent Performance

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Fitz98

Joined
Mar 17, 2011
Messages
933
Location
Florida
Ever since I bought my 03 Suburban 5.4 years ago, I have always had AC issues under certain conditions and 3 mechanics have not been able to diagnose it.
AC has been serviced and levels and pressures checked.
Problem only starts when I am at idle in hot weather for too long. Eg, today was 90 degrees, I sat at idle in a parking garage for about 5 minutes. Started cool initially, then started blowing warm after a short while. I can feel a little bump in idle when the compressor goes off and doesn't come back on again.
Up until recently, once I got up to highway speeds, the problem would correct itself. Now if the problem starts it will not correct itself, until I stop the vehicle and let it cool down. Today's example was blowing warm for an hour of my trip (after it failed)...if I would have started driving right away, there would not have been a problem. I tried turning ac on and off, cycling hot to cool temperature settings, switching between modes and zones and nothing worked to kick on the compressor. I stopped for an hour, restarted and got right up to in-town driving speed and it blew cold ever since.
I don't think it is a blend door issue, it seems like the compressor clutch is not engaging under certain conditions.
What would cause the compressor clutch to only engage some of the time...ie while driving, but not at idle?
Any trouble shooting ideas?
 
I had thought that the rear evap commonly leaks on GM vehicles.

I do know that on our GM, I would hear a hiss which when googled implies low refrigerant, so I recharged and was able to get less than 1/2 a can in. didn't get rid of the hiss.

Since I really don't remember if that hiss were always there I gave up. I thought maybe it has to do with what's called a TXV on home AC. the GM is the only car of our 3, which doesn't make the driver uncomfortable with the AC running and it's not that hot outside. I measured the vents to be 51F to maybe 48F at best, when ambient were 75F. The other two cars were kissing 40F....

I wonder if your results are any different if you leave the rear AC off....
 
Blend door would have nothing to do with the compressor not engaging. If the compressor is cutting out you need to attach a gauge set and a scan tool while the problem is happening. Monitor the pressures (on the gauges and electronically to make sure they match) as the system loses cooling.
Possible causes could be high pressure cut off due to lack of airflow over the condenser or a restriction inside the condenser. A bad high side pressure transducer or low pressure cut off switch would cause this as well. I also believe your truck has a fixed orifice type refrigerant metering system, which could be partially clogged.
Also, if your truck has a variable displacement compressor the solenoid on the compressor is notorious for failing. I change GM compressors all the time because of this failure and the solenoid is not available separately.
My bet is airflow through the condenser. If the system gets cold once you start moving, that's an airflow problem. Fan operation or debris in the condenser fins.
 
Fitz98 said:
compressor goes off and doesn't come back on again.
Click to expand...
This is common as the compressor clutch wears and the gap increases until it doesn't always pull in when energized. High temperature underhood such as from sitting at idle causes the electromagnet to become weaker (resistance of copper winding increases).

The gap is usually adjustable by removing shims. Old GM compressors had the clutch plate simply pressed onto the shaft and there was a special tool to move it on and off to the desired gap, but I don't think it was like that in 2003.
 
AC evaporators have a temperature sensor. The temperature data are sent to the climate control module. If the sensor sees about 37*F (evaporator on the verge of freezing up) the climate control module will disengage the compressor clutch and allow hot coolant to flow through the evaporator. This increases its temperature and prevents the freezing up of the evaporator. The first step would be to have a shop scan the climate control module for both codes and to see what the evaporator temperature sensor is seeing. The sensor could be the culprit.
 
mk378 said:
This is common as the compressor clutch wears and the gap increases until it doesn't always pull in when energized. High temperature underhood such as from sitting at idle causes the electromagnet to become weaker (resistance of copper winding increases).

The gap is usually adjustable by removing shims. Old GM compressors had the clutch plate simply pressed onto the shaft and there was a special tool to move it on and off to the desired gap, but I don't think it was like that in 2003.
Click to expand...
This had one of the mechanics scratching his head. This was years ago, but if memory serves, he was able to bypass some of the electronic controls to directly energize the compressor clutch, but the clutch would only intermittently engage when the temperature was set at the lowest setting, so I just left it set at 60 degrees all the time. As long as I didn't sit at idle too long, this usually worked.
Does sound most like a clutch engagement issue to me. Acts up more when the temperature differential is too great. Less issues when the temperature is below 80 and I set it at 60, than when the temperature is 90 and I set it to 60.
Your theory makes sense.
 
CarDoc66 said:
Blend door would have nothing to do with the compressor not engaging. If the compressor is cutting out you need to attach a gauge set and a scan tool while the problem is happening. Monitor the pressures (on the gauges and electronically to make sure they match) as the system loses cooling.
Possible causes could be high pressure cut off due to lack of airflow over the condenser or a restriction inside the condenser. A bad high side pressure transducer or low pressure cut off switch would cause this as well. I also believe your truck has a fixed orifice type refrigerant metering system, which could be partially clogged.
Also, if your truck has a variable displacement compressor the solenoid on the compressor is notorious for failing. I change GM compressors all the time because of this failure and the solenoid is not available separately.
My bet is airflow through the condenser. If the system gets cold once you start moving, that's an airflow problem. Fan operation or debris in the condenser fins.
Click to expand...
This also makes sense.
I would imagine pressures change with ambient temperature. Only thing with the airflow theory is that it does not always correct itself at highway speeds.
Any of the partially clogged conditions could be possible.
The trouble I had at one mechanic is that I could not duplicate the problem when he was diagnosing.
Maybe now that the weather is hotter and the problem is more consistent, I could take it back and have him re-diagnose.
Sounds like it would need diagnostic equipment to troubleshoot without throwing a bunch of parts and sensors at this, plus I don't have equipment to capture and recharge the system to go replacing parts.
Would love to know people like you in my area that understand these things and have equipment to diagnose and narrow down the issue.
 
I think Chris might be onto something, but I'll admit that I know almost nothing about diagnosing A/C problems.

Your problem sounds at least similar to something that was happening to my 2001 5.3 Silverado. Where I park for work, there's a lot of low-speed driving interrupted by several stop signs and stoplights before I can drive at a steady speed for any length of time. In fall and spring, when outside temps are fairly mild but it's hot in the truck after it sits in the sun all day, the air would start blowing hot when I got stuck at the second or third stoplight. I could hear/feel a change like you described, and the vents would start blowing unconditioned air. Once I got moving again, the cold air seemed to come back.

I more or less ignored trying to fix anything and came up with the theory that the radiator and condenser weren't putting out enough heat to activate the fan clutch at the beginning of the drive.

The fan clutch "seemed" OK. It barely turned either cold or hot, it would hold a piece of paper against the grille when running, and engine temps were always consistent. I finally changed it (with an OEM clutch) last June after an out-of-character high temp reading in the school pickup line. Now the air is cold all the time.
 
Fan clutch seems like an easy enough thing to do, maybe worth a shot to start.
222k miles, so I am sure it is due anyways
 
The fact that it doesn't always cool down once you get on the freeway makes me believe it's not an airflow problem (fan related).
The trick is to catch it when it's not working, otherwise you're throwing parts at it and that's frustrating. Good luck with it.
 
mk378 said:
This is common as the compressor clutch wears and the gap increases until it doesn't always pull in when energized. High temperature underhood such as from sitting at idle causes the electromagnet to become weaker (resistance of copper winding increases).

The gap is usually adjustable by removing shims. Old GM compressors had the clutch plate simply pressed onto the shaft and there was a special tool to move it on and off to the desired gap, but I don't think it was like that in 2003.
Click to expand...
There is a very simple way to diagnose this issue. Just tap into the positive (+) wire feed going into the compressor's magnetic clutch coil with a test light and ground the other end. Turn the A/C to high and see if the clutch disc engages 100% of the time when the test light illuminates. If the light comes on and the compressor clutch does not engage the clutch disc air gap is too large. It is unlikely that the magnetic coil would work intermittently. On older vehicles, the gap often increases due to rust jacking on the backside of the disc that is not visible until the disc is removed. I have fixed excessive air gaps by simply removing the rust with a wire brush and leaving the factory shim washers intact.

Be careful not to lose the very thin shim washers behind the disc. You can borrow a free loaner tool from Advance Auto or Autozone to hold the disc when unbolting and installing the disc.
 
The really simple test to see if it is clutch gap, which really should not be done because it is dangerous, is to smack the clutch plate with a suitable wooden stick with everything up and running while the clutch is supposed to be engaged but it is not. If it snaps in and starts cooling, 100% it is the clutch gap. If it doesn't then next you'd investigate if the clutch is receiving power. Relays also have a coil of copper wire that gets weaker when hot. I would assume that since the OP has been to several experts, the clutch relay has been replaced at least once.
 
Had same issue with my son's Durango. Would just stop cooling at times (his description). All components seemed fine, I finally got it to do it - checked power to a/c clutch - yep. Clutch replacement was easy, Sanden compressor.
 
Chris142 said:
Fan clutch
Click to expand...
Yeah, I'd throw a fan clutch at it. I think 03 is the last year before they switched to E-Fans. Better yet, if you want, do a good quality E-fan conversion if you're going to keep the vehicle a long time. Better MPG, better performance when cold, and better AC performance when hot.

When I had my 01 Suburban with about 290K miles the temperature would creep up under low speed/high load conditions (off-roading, for example) but in 99% of driving it worked fine so I never would have noticed it if I didn't take it off-roading. For regular daily driving, around town or on the highway, the worn out fan clutch was good enough. Replacing that solved the problem. I sold the vehicle shortly after so didn't bother with E-fans but if I keep my Yukon long-term I will convert it for sure. Just not going to invest that when IDK if I'm going to sell it soon.
 
I had a similiar issue with my 02 Envoy.

I was able to remove the center bolt and pull the front of the pulley, I think it was part of the clutch.

I removed the thin washer or shim and reassembled. Never a problem after that.

What others are saying about the air gap of the clutch could be the issue. I believe when the gap is too big, the clutch slips a little then begins to overheat, which causes the compressor to shut down.
 
I have an 05 Yukon XL with AC issues too. The rear AC works perfect so the rear passengers are happy but up front it is iffy. Sometimes it works great and other times it blows heat. It has an electric fan on the radiator that does run and I can hear the compressor cycling. Was able to add about 1/2 a can of 134A and gauges showed it was a little low. Only took that 1/2 can and still is a little low. Sometimes when my wife pushes recirc it starts cooling good other times not. The way all electronic stuff in it starts to fail with age I just assume that is the problem.
 
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