# 2500HD Intermittent AC problem



## WBHB (May 26, 2004)

I have a 2002 Chevy 2500HD, 160K miles, that has an intermittent AC issue. When I am rolling down the freeway, the AC works great. Sometimes, when I bring the truck to an idle, the compressor seems to kick out and it begins blowing hot air. This is much more pronounced when it is hot (> 90 deg) outside. I can overcome this by accelerating and the compressor kicks on and will eventually start blowing cold air again.

I have looked and looked and looked on the interweb to find a similar issue or problem, but haven't been completely successful. I did find one site that suggested I replace the compressor mounted high cut-out pressure switch. Since these are generally less than $10, I thought I would give it a try before paying someone an arm and a leg to troubleshoot and tell me I needed to replace the compressor and all.

Anyway, when I look for pressure switches online, I find several high cut-out pressure switches. They differ by what is described as OFF and ON, which I am guessing is some pressure indicator where they flip off and on. 

How would one decide whether to use a 455 off 255 on, a 20 off and 40 on, a 370 off 263 on, or a 470 off 270 on switch. 

Thanks in advance. Also, if you think I am going down the wrong road with my diagnosis, please let me know.


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## DirtyBirdShot (Apr 26, 2010)

X2

Same problem on the Wife's '05 Suburban.


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## #1grandpa (Jun 24, 2006)

SAME HERE ON MY 02 2500HD


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## Cowboy1uhB (Nov 19, 2008)

*Same on '04 2500 136K miles*

I had my fan clutch replaced when the a/c would begin to blow hot air at highway speeds. I now believe it to be one of the switches you are talking about. Now when it blows hot air, I put it in neutral, turn engine off and restart....cold air returns. 
Right now it idles rough when A/C is on. Air is usually hot while at idle until the rough idle smooths out. This leads me to believe the compressor is dragging the engine down somewhat...I'm at a loss also.


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## ralph7 (Apr 28, 2009)

make sure the compressor is actually kicking out.
another problem could be the motor that controls the heat door is letting heat in w/your cold air.


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## Pier Pressure (Aug 30, 2009)

You might have a vaccuum leak somewhere.


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## El Ahogo (Mar 14, 2010)

sounds like theres a problem with your air conditioning system..


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## millertym_1978 (Apr 13, 2006)

*a/c*



Cowboy1uhB said:


> Now when it blows hot air, I put it in neutral, turn engine off and restart....cold air returns.
> 
> This is exactly what my buddy told me to do that owns a mechanic shop. So far it resolves the issue.


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## Old Baitbucket (Sep 13, 2007)

There is a safety switch in the system that will not allow the clutch to activate when the system gets low on freon. I have had one that was intermittent and would act like the problems you describe. I think it had a needle valve underneath it so the freon wouldn't escape when you changed it. 
Also had a Ford that would stop cooling if blower was on high. That turned out to be the air gap on the clutch was to wide. I guess the high blower would pull the voltage down and clutch wouldn't pull in. I adjusted the gap with a hammer and it worked good ever since.


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## huntnetime (Jul 23, 2004)

Same here on 2000 model 1500 z-71 w/ 5.3L motor...


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## FL (Oct 13, 2004)

I had the same problem with a 2000 Silverado. The ac clutch had worn. I was able to adjust the ac clutch. Warning! Almost every shop I took it to said the compressor had to be replaced. 
To check the ac clutch:
Remove the air dam below the radiator.
With engine running and the ac blowing hot air, tap the very front of the ac compressor with a wood hammer handle or something similar. If the compressor kicks in, the fan clutch is worn.
STAY AWAY FROM THE FAN AND MOVING PARTS!!

Google ac clutch air gap for more info.

Fred


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## D.L. (Sep 13, 2007)

Is it happening when your running it on recurculate?


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## Smitty (Jul 1, 2005)

same problem - 2005 Tahoe
Turn off truck and restart. Fixes problem every time but it has been happening more often. Once a week now versus once a month (about the past 5-6 months). Been told it has something to do with a damper but don't know the validity to that. Taking the truck in for scheduled maintenance within a couple of weeks and will post with diagnosis.


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## MilosMaster (Aug 18, 2005)

*Same Problem*

I have the exact same problem with my '04 2500HD with around 85K miles. It only happens when it is really hot and is usually solved once I get on the freeway or, if in town, turn the engine off and back on. Looking forward to anybody getting a definitive answer/solution!


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## PasadenaMan (Dec 5, 2007)

Same issue on my 1999 newer body style silverado 5.3L I have to turn it off for 2 minutes to get it to cool for another 20 minutes.
subscribed. Partsgeek has the clutch for 60 bucks. might buy that.


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## bill (May 21, 2004)

FL said:


> I had the same problem with a 2000 Silverado. The ac clutch had worn. I was able to adjust the ac clutch. Warning! Almost every shop I took it to said the compressor had to be replaced.
> To check the ac clutch:
> Remove the air dam below the radiator.
> With engine running and the ac blowing hot air, tap the very front of the ac compressor with a wood hammer handle or something similar. If the compressor kicks in, the fan clutch is worn.
> ...


yep, sounds like their clutch is slipping
fords have the same problem
http://autoforum.classifieds1000.com/Ford-F250/a_c_blows_hot_air


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## Puma (Jun 16, 2009)

WBHB said:


> I have a 2002 Chevy 2500HD, 160K miles, that has an intermittent AC issue. When I am rolling down the freeway, the AC works great. Sometimes, when I bring the truck to an idle, the compressor seems to kick out and it begins blowing hot air. This is much more pronounced when it is hot (> 90 deg) outside. I can overcome this by accelerating and the compressor kicks on and will eventually start blowing cold air again.
> 
> I have looked and looked and looked on the interweb to find a similar issue or problem, but haven't been completely successful. I did find one site that suggested I replace the compressor mounted high cut-out pressure switch. Since these are generally less than $10, I thought I would give it a try before paying someone an arm and a leg to troubleshoot and tell me I needed to replace the compressor and all.
> 
> ...


This sounds like to me you have a situation where you lack air flow over the condensor. This will cause the high side pressure to rise really high and kick off from the high side switch.

Before I would bother with installing different switches get some guages and you will see at what pressure it is kicking off. This will tell you if it is working properly.

I have no idea if that truck has an electric fan that blows over the condensor or not. If it does, is it working? If not the symptoms you describe are exactly what would happen if no air passes over the condensor! Also, a bad fan clutch could cause this as well.

I would NOT replace the high side switch with anything other than what the factory specs.

getting guages and using them will answer a lot of questions.


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## Barrett (Jun 6, 2005)

Its either the Pressure switch - the clutch - or vacuum sensing line has hole rubbed in it


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## Archer (Jul 10, 2006)

Same thing on my 04. It didn't matter where I was though, just started blowing hot air. Shut it down, start it up and problem gone. Also had problems with the control switch, only ran on #5. When it started blowing hot all the time I took it in and they replaced a relay which seemed to solve both problems but this week the A/C started kicking out again.


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## the mechanic (Nov 8, 2006)

*ac problems*

hey i work for chevy- ac cutting out on low idle is a worn clutch- needs new compressor- tapping on it with a hammer is a sign that the gap is to much for magnetic field to engage- you can replace clutch only but usually if clutch is worn -so is compressor!!! and ac blower blows on high only is a bad relay located behind gluff compartment- also check pressure switch located under hood- passenger side, screws into accumilator-if its oily-its leaking freon- this is best advise i know- just put new compressor on my own 03 2500 chevy with 164000 miles!


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## D1MEKANIC (Feb 1, 2009)

A weak clutch field coil, worn clutch (too much air gap) low voltage to clutch coil and low engine idle are some of the reasons a clutch will not engage. If it kicks out at idle, first check the idle speed. If it is low and surging and as a result turning compressor off, then clean throttle body by wiping the residue behind the throttle plate with a rag soaked with a cleaner. This is a common issue on trucks without a throttle cable (drive by wire). Do not spray cleaner directly into throttle body as the solvent can get into the motor and sensor and destroy it. Otherwise, as stated above, check for a weak clutch or low voltage, which could come from the relay or a weak clutch cycling switch on the accumulator. Hope this helps some of you guys.


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## rjc1982 (Sep 27, 2005)

Cowboy1uhB said:


> Now when it blows hot air, I put it in neutral, turn engine off and restart....cold air returns.
> 
> Your issue here is with the blend door motor and/or control. GM has a re-flash for the HVAC module that will correct that issue.


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## rjc1982 (Sep 27, 2005)

Sandhog said:


> same problem - 2005 Tahoe
> Turn off truck and restart. Fixes problem every time but it has been happening more often. Once a week now versus once a month (about the past 5-6 months).


See my previous post, this is the same issue that can be resolved by a flash update to the HVAC module. Find a shop that has a J2534 compliant re-flash tool and they should be able to take care of this for you. Most shops charge $100-$125 for a re-flash, but I know that Brake Check can perform re-flashes and only charges $75.


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## fish1kemah (Feb 26, 2009)

Recently had the same problem , check the AC coils in front of the radiator , mine was full of dead bugs and tons of dirt , cleaned them off and a shot of freon and no more problems,

F1K


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## kck (Feb 13, 2006)

rjc1982 said:


> See my previous post, this is the same issue that can be resolved by a flash update to the HVAC module. Find a shop that has a J2534 compliant re-flash tool and they should be able to take care of this for you. Most shops charge $100-$125 for a re-flash, but I know that Brake Check can perform re-flashes and only charges $75.


I don't know about the re-flash but replacing the hot/cold actuator located under the dash will fix the problem. There is one for the passenger and driver side.


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## bigfost (Oct 11, 2004)

Very interesting thead. My '04 was doing the same thing. I took it to my mechanic friend who said he couldn't find anything wrong, but it was 1/4 can low on Freon. He topped it off and I haven't had any further problems.


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## huntnetime (Jul 23, 2004)

I'm beginning to suspect a very dirty condenser coil as well on my truck. I've owned it since it was new(11 years) and this started happening last fall. I replaced the low-pressure switch just for grins since it is a cheap part, but it still malfunctioned. I've checked the refrigerant and it seems to be good. Then I remember reading in my manual about the cabin air filters. I then realized I had never changed them. EVER. Now, I am really good on maintenance on my truck, but this is one item I overlooked. I pulled the filters out and they looked like something out of a horror movie. BLACK, bugs, leaves, dirt, soot...you name it. I did my best to clean the evaporator coils with an air chuck and shop-vac and replaced filters with new ones. It's helped a little bit. BUT, I've never bothered to do a good cleaning on my condenser coil in front of the radiator. I'm going to check that in the morning and see if it helps. I'll let y'all know how it goes.


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## t_willy (Jan 28, 2010)

rjc1982 said:


> See my previous post, this is the same issue that can be resolved by a flash update to the HVAC module. Find a shop that has a J2534 compliant re-flash tool and they should be able to take care of this for you. Most shops charge $100-$125 for a re-flash, but I know that Brake Check can perform re-flashes and only charges $75.


You are correct. They can hook up a scan tool and re-calibrate the actuators. If the re-calibration does not work you have to replace the actuators wich are located behind the dash. There are a total of four and why they are in there I would advise to replace all four. If you are having to turn your vehicle off and then on again to get it to blow cold this is definitely your problem.


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## WBHB (May 26, 2004)

huntnetime said:


> I'm beginning to suspect a very dirty condenser coil as well on my truck. I've owned it since it was new(11 years) and this started happening last fall. I replaced the low-pressure switch just for grins since it is a cheap part, but it still malfunctioned. I've checked the refrigerant and it seems to be good. Then I remember reading in my manual about the cabin air filters. I then realized I had never changed them. EVER. Now, I am really good on maintenance on my truck, but this is one item I overlooked. I pulled the filters out and they looked like something out of a horror movie. BLACK, bugs, leaves, dirt, soot...you name it. I did my best to clean the evaporator coils with an air chuck and shop-vac and replaced filters with new ones. It's helped a little bit. BUT, I've never bothered to do a good cleaning on my condenser coil in front of the radiator. I'm going to check that in the morning and see if it helps. I'll let y'all know how it goes.


No doubt I am probably in the same boat. I changed my in-cabin air filter once probably 7 years ago, but haven't touched it since. Now that you mention it, it was pretty filthy around the evaporator coils if I remember correctly. Getting the condensor coil clean is also on my list to look at on Friday morning.

PS: I called around a couple of places, and they all immediately said that it sounded like my compressor was bad and needed replacement. When probed, some admitted that my problem may just be the clutch, but no one was interested in just replacing that. The lowest price quoted was around $1000. Of course, the dealer wanted to bend me over as usual.

I started looking up parts yesterday on line, and my 02 clutch only appears to come with the compressor attached. That's in the $250-300 range. Add a new accumulator and freon and we are in the $350 range. I am hosed since I don't have the tools to charge a system myself.


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## Never easy (Mar 20, 2006)

rjc1982 said:


> Cowboy1uhB said:
> 
> 
> > Now when it blows hot air, I put it in neutral, turn engine off and restart....cold air returns.
> ...


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## WBHB (May 26, 2004)

Replaced the in cabin air filters this evening and tried for 45 minutes to see of I could reproduce the problem . So far so good. Knock on wood. Fingers crossed. We will see.


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## 6.5 shooter dude (Jan 8, 2008)

WBHB said:


> I have a 2002 Chevy 2500HD, 160K miles, that has an intermittent AC issue. When I am rolling down the freeway, the AC works great. Sometimes, when I bring the truck to an idle, the compressor seems to kick out and it begins blowing hot air. This is much more pronounced when it is hot (> 90 deg) outside. I can overcome this by accelerating and the compressor kicks on and will eventually start blowing cold air again.
> 
> I have looked and looked and looked on the interweb to find a similar issue or problem, but haven't been completely successful. I did find one site that suggested I replace the compressor mounted high cut-out pressure switch. Since these are generally less than $10, I thought I would give it a try before paying someone an arm and a leg to troubleshoot and tell me I needed to replace the compressor and all.
> 
> ...


I did not take time to read the responses sorry if it's already covered. If you have a drive by wire TBI (means there is no cable from the accelerator petal to the throttle body) The idle is too low and you need to clean your TBI unit. This is a very common issue.


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## quickrick (Aug 10, 2009)

We fix these @ my shop everyday. Excessive a/c compressor clutch air gap. Correct repair is to replace the compressor, however you can buy a little time by adjusting the clutch air gap. ase master tech


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## jaime1982 (Aug 25, 2009)

its a chevy....... of course ur gonna have problems ur gonna have to pay for!!!!! duh......


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## WBHB (May 26, 2004)

After replacing the in-cabin air filter last night, this morning, I took my truck down to the car wash and power washed the condensor coils in front of the radiator in an effort to get more effecient air flow thru the system. I also checked the fan clutch by spinning it. It only went about an eight of a revolution. I was told if it free spun, you should probably replace the clutch.

Also, I have since cleaned the throttle body assembly and replaced the fuel filter in an effort to get the engine to run at higher RPM's at idle, just in case. Heading out now for pretty good drive with stops and starts, so hopefully somewhere, I have lucked into a lower cost repair. I am just having trouble with the idea of a vehicle with 4300 hours on it has a bad compressor. 

Thanks for all your replies and advise. David


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## CCRanch (Jul 8, 2006)

my '06 does the same thing. Called a A/C shop in Baytown and he immediately said it was the motor under the dash. I have the spilt controls for the driver and passenger sides, and only the driver side gets hot. This happens almost everyday. I shut it off and start it back up and it blowsd cold again. He wants $700 to change out the motor.


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## sabine lake hustler (Dec 17, 2007)

Cowboy1uhB said:


> I had my fan clutch replaced when the a/c would begin to blow hot air at highway speeds. I now believe it to be one of the switches you are talking about. Now when it blows hot air, I put it in neutral, turn engine off and restart....cold air returns.
> Right now it idles rough when A/C is on. Air is usually hot while at idle until the rough idle smooths out. This leads me to believe the compressor is dragging the engine down somewhat...I'm at a loss also.


you can fix the rough idle by pulling the air intake off and clean around the butterfly manifold with a manifold cleaner. she will ideal smooth like a champ again.did this for both my tahoe and tundra. taho- as for the AC i have the same issue. just started 03 244K miles.


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## Smitty (Jul 1, 2005)

*2005 Tahoe AC issues*

Going to revive this thread. Took my truck in today for inspection/general maintenance etc. Knowing I had the AC issues as everyone else does, I asked them to check. Dealership advised that 2 AC acuators needed to be replaced. Parts and labor $1250. Is this price out of whack ? I haven't a clue in regards to this price. If I replace 2, any reason why I should not replace all 4 (assuming I keep the truck for 5+ more years and it won't break me). Thanks for the advice.


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## Smitty (Jul 1, 2005)

Just been advised there are not 4 acuators but 2 AC acuators and 1 recirculating acuator.


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## Neck-deep (Jun 27, 2007)

I've got an 04 Duramax and have been having problems with my A/C as well. I took it in last year and the mechanic found that my A/C computer was failing to turn the compressor on at normal intervals (A problem due to it not turning on at certain cab temperatures) $$$=computer. This caused hot/cold air at times (more hot than cold at times). Eventually, the hot air would continue to blow without any cold and I just took it in. Worked great until a month ago.

Now I'm having the same issue again, hot and cold. So I took it in to my mechanic a month ago because I was going on a road trip the next day and he sprayed water towards the radiator having me accelerate to 2500 RPMs. This worked for a while but he said I'd eventually have to bring it back to get something in there cleaned. I'm taking the truck to him today to have the A/C worked on. I'll post later as to what the problem was this time.


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## CCRanch (Jul 8, 2006)

*Fixed??*

Well, my batteries went dead 3 weeks ago and I replaced them, and since then, I haven't had a problem with my A/C blowing hot. Maybe it reset something when I disconnected the batteries, or maybe a coincidence. Either way, might be worth trying. It seems to have fixed mine.


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