Intermittent A/C problem; blows slightly cool air

Tiny
PAULH241
  • MEMBER
  • 2002 CADILLAC ESCALADE
  • 130,000 MILES
2002 Escalade. Sometimes, the A/C suddenly stops blowing ice cold air, and starts blowing slightly cool air. Its the same at both the front and rear vents. I put a thermometer in the drivers side vent to track actual temperature coming out of the vent. When it's working, it blows around 45 degree air. When it's "not" working, it blows 78 degree air. Outside temp is always hot when this happens, like 95-105 degrees. But, sometimes it works fine when it very hot outside. I tapped into the A/C compressor wire and ran a small indicator light into the vehicle. So, the light comes on whenever the compressor is running. The compressor DOES run, I can see the clutch engage, a noticeable load hits the engine and the condenser fan turns on. When the vent temp runs up to 78 degrees, the compressor IS running. To eliminate the possibility of a heater valve issue, here's what I did: I turned off the A/C and moved the temperature control knob to the hottest setting. The vent temp went to 150 degrees (hot!). Then, under the hood, I put clamps on the input AND return lines for the heater core. The vent temp almost immediately dropped to 90 degrees, which was the temperature in my garage at the time. Then I drove around for 2 days, same problem. Only slightly cool air on day 1 and icy cold air on day 2.

The vehicle has been to 2 separate shops. Both shops discharged the system, checked for leaks and recharged the system. There were no leaks and the system was not low on freon. Of course, it worked fine while they had the vehicle. Can anybody help. Please?

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Friday, August 30th, 2013 AT 8:24 PM

9 Replies

Tiny
TY ANDERSON
  • EXPERT
Do you have the air conditioner set to auto when the temperature change happens or on manual mode?
Does the above concern happen more frequently when the vehicle is idling and not so much when driving? The manufacture has release a technical service bulletin on the cooling fans not cooling sufficiently when idling for extended period of time such as sitting in traffic.
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Friday, August 30th, 2013 AT 11:50 PM
Tiny
PAULH241
  • MEMBER
I always run the system in manual mode. However a few times I've moved both the fan speed switch and the vent selector switch to AUTO. Made no difference. I've also tried just the fan speed switch on AUTO and just the vent selector switch in AUTO. No change in vent temp when I do this.

The problem happens both at idle and at highway speeds. I've always noticed that the A/C isn't as cold at idle on this car. But this problem came on suddenly about 2 months ago while on a road trip. Was driving on the highway and it was 105 degrees outside. Didn't have a thermometer at that time but I assume the vent temp suddenly raised from ice cold to 80 degrees or so. Never touched the controls before the problem happened but I did start trying different settings after the problem started. Suddenly, when we were back in town and about 4 miles from home, it started blowing ice cold air again.

As a troubleshooting step, I've taken the car on the highway when it's acting up. It only very slightly lowers the vent temp (about 4 degrees or so).

Also, I've taken it on the highway when it's working fine. Then I notice a bit more of a drop in the vent temp compared to idle (about 10 degrees), but because its still nice and cold at idle, there's no complaints from the family.
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Saturday, August 31st, 2013 AT 7:16 AM
Tiny
TY ANDERSON
  • EXPERT
Intermittent issues can be one of the worst diagnostic jobs given in my profession! Obviously the key here is get the a/c system to act up all the time so a proper diagnostic can happen. Unfortunately there are so many variables that can cause the above concern to happen. Is it a mechanical or electrical issue? A Ambient (out side the vehicle) temperature sensor signal can drop out (.-40Deg.) Causing the climate control module to shut down the climate control. A restriction in the refrigerant pipes could be causing a intermittent freeze up (internally). Broken temp blend door sticking open enough to allow hot air through. Temp blend door actuator internal gears worn causing door to stay open. Faulty wiring to a pressure sensor signal or any input or output wiring to control module
I would first try to pull any diagnostic fault codes from the climate control module to see if there are any code or history codes (the code will start with a B [or bxxxx] followed by four numbers). You'll need to get a hold of someone with a factory compatible scan tool to do this and access the module. If there are any codes this would certainly narrow down where to start testing.
As I mentioned before there is a TSB (reference number 01-01-39-004) which describes a loss in a/c cooling and the correction is to add a auxiliary cooling fan to increase air flow through condenser to assist in removing more heat.
Hope this helps you, TY
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Saturday, August 31st, 2013 AT 9:46 PM
Tiny
PAULH241
  • MEMBER
Thank you for replying and for the information, it's very much appreciated. Just a few more questions to help me further isolate the issue. You mentions a possible blend door issue. I think I isolated that as a potential issue by clamping the heater hose lines that feed the heater core. I then proved the clamps were working (cutting off ALL hot water to core) by turning the heat to full. There was no heat coming out of the vents. If the blend door was sticking, AND the AC compressor was running, could a faulty blend door still cause this problem given that the heater core's functionality was as removed from the system? Also, since the compressor is always running when the issue is present, I've been assuming a temperature sensor is not to blame. Is this a correct assumption? I think the only control over cooling that the system has is the blend door and the control (on/off only) of the compressor. Is that also a correct assumption? I mean, the climate control system processor can't regulate the orfice tube and can't regulated the amount of pressure supplied by the compressor, can it? When the AC is working well, the compressor cycles on and off regularly while driving around town and the vent temp stays in the low 40's.

Since the AC worked for years with no trouble, and suddenly started having issues, I'm not sure adding the extra fan across the condensor would be the problem. But I'm willing to try. I'll check on the service bulitine

Put gauges on the system today. Around 275 psi high side and 70 psi low side. AC was blowing pretty cold today.

Thank you again.
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Sunday, September 1st, 2013 AT 12:37 AM
Tiny
PAULH241
  • MEMBER
I checked today and discovered the Escalade already has that Aux fan installed in front of the condenser. It must have been done by a previous owner. I've always noticed the fan, it's fairly loud. I just never new it was something added later to the vehicle. I always just assumed it came from the factory that way. Do you know how or where I can get a diagram or illustration of the entire AC system?
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Sunday, September 1st, 2013 AT 8:16 PM
Tiny
TY ANDERSON
  • EXPERT
I have access to about 26 images for the automatic air condition system. Most of them are wiring diagrams. Is there something specific your looking for?
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Wednesday, September 4th, 2013 AT 9:50 PM
Tiny
BOBBYBIZZAL
  • MEMBER
Your problem might not be any of those. I had the same type of problem. My escalade has the digital settings for the AC heat, speed, etc. If yours is a digital type, there is a blower and a blower relay. The blower relay can cause lack of heat, cool air, etc. I changed my blower and relay last summer, no problems since. The relay is up under the passenger side under the cover along with the blower. Easy to change. I recommend YOUTUBE for the proper way to take stuff apart!
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Tuesday, October 8th, 2013 AT 11:49 AM
Tiny
BOBBYBIZZAL
  • MEMBER
Blower is about $100 at Advanced auto and the blower relay is a little more. The relay isnt going to look like your old one. Dont worry about it, follow the instructions, you might have to solder a wire yourself. Walmart has soldering guns with solder for ten bucks.
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Tuesday, October 8th, 2013 AT 11:52 AM
Tiny
PAULH241
  • MEMBER
Thanks for that info. My escalade does not have the digital controls, just the regular knobs. Just a quick question. Did your blower stop working? I mean did you have no air blowing from the vents? If your blower still worked. You may be on to something that I need to look at.

This is such a frustrating problem. Since there's soooooo many issues with the blend doors on the Escalades and Tahoe's, almost everybody jumps straight to that as the problem with my Escalade. But, in my case, it's absolutely not the problem.

The fan/blower works perfect. The air out of the vents It gets hot when I move the knob to red and, 90% of the time, it gets ice cold when I move the knob to blue. But the 10% of the time that it doesn't work is miserable. I mean, it's not blowing hot air, it just blows ever-so-slightly cooled air. Probably like 85* or so. Of course when it's 110 degrees outside slightly cooled air from the vents is not going to do much.

I think the problem may be related to something in rear AC/heater area. I assume with this split system, having two expansion valves and evaporators but only one compressor, if one expansion valve acts up then the entire system pressure could be affected. Since the front expansion valve (orifice tube) has been replaced twice, I'm gonna tell the shop to replace the rear valve next time I take it in.
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Wednesday, October 9th, 2013 AT 4:16 PM

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