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Ac Is Warm While Idling


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#1 xtmsports

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Posted 11 September 2009 - 09:42 AM

Hi Guys,

I have a 2001 Chevy Tahoe with the 5.3L engine.

I have an odd issue with the AC and was hoping an expert can shed some light on the problem.

When the truck is driving, the AC is ice cold. However, when I am idling for a couple of minutes, the AC will start to blow warmer air. Almost as if the ac is turned off and only the blower is working.

Can somebody please assist?

Thanks.

#2 txab

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Posted 11 September 2009 - 09:50 AM

Sounds as if you're not moving enough air through the condenser when sitting still. One thing to check is your fan clutch. Make sure it is locking up when it should. If you still have the original factory clutch it's probably due for a change. Do you still hear a good roar from underneath the hood when it's hot? Your fan should definitely be locked up and providing max air. You can also see if your ac clutch is disengaging at idle. Take a look at it see if it's turning. If it's not take something and tap the face of the clutch and see if it pulls in. Of course while you're doing this be careful and watch for all the moving parts on the engine. If it pulls in your clutch air gap may be too wide or you may a have weak AC clutch.

Edited by txab, 11 September 2009 - 09:59 AM.

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#3 spurshot

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Posted 11 September 2009 - 10:19 AM

I'm thinking fan clutch as well. However, try asking over at the forum section of ACkits.com They are great folks with good techs.

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#4 duce

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Posted 11 September 2009 - 10:31 AM

Actually doesn't seem too vexing my brother. When you are at idle, you are not producing as much pressure as when you are accelerating. So if your freon levels are low, then when you idle you very well may not get any cold air through the vent. As A/C runs like a giant circle of pressure, you need to make sure all the levels are sustained at all times.

Before diving into a fan clutch, cycle switch, etc. I would just simply try to evacuate and recharge the system, and I am willing to be that it takes care of the problem. Just run to your local auto parts store, find a few bottles of R-134A, and load them up into the system through the low-side fitting. The fittings will be located in the upper-left hand corner of the engine compartment (if you're looking INTO the compartment) coming off of the condensor. The low side will be a smaller fitting than the high side, and normally it's the closest one in-line to the condensor.

Start with about a full can of freon, and check to see how it feels. After that, use half a can at a time to be certain you don't overcharge the system. Might want to pick up some UV Dye as well, so in about a week you can run a black light over the truck to identify any leaks.

Hope this helps brotha, and that it's something simple like this and not something serious. Have a good one!
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#5 Won_Hunglo

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Posted 11 September 2009 - 11:22 AM

Post your pressures & temps.

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#6 ShoddyHog

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Posted 11 September 2009 - 12:04 PM

Start with about a full can of freon, and check to see how it feels. After that, use half a can at a time to be certain you don't overcharge the system. Might want to pick up some UV Dye as well, so in about a week you can run a black light over the truck to identify any leaks.


Freon? In a 2001 Tahoe? That'd be a hoot.

OP, is your compressor clutch engaged when it is blowing hot air, or does the compressor kick off? If it stays on, check the clutch like the others suggested, but if it is kicking off, then you either have a low or high pressure.

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#7 spurshot

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Posted 11 September 2009 - 01:38 PM

You really can't tell squat without pressures. Most people don't have a gauge set. Adding refrigerant blindly is potentially harmful to the system, it could hydraulic some parts and cost a bit of coin to fix.

Taking the pressures and temperatures at the vents and condensor will go a long way toward a proper diagnosis, rather than shooting in the dark. I'd recommend you get some good gauges and a Therma-pen "instant" thermometer or take it to a shop if you are not so inclined to learn and tool up for HVAC system repair/service. The tools necessary for proper service will run into a couple to a few hundred dollars or about what it'll cost for a single servicing. It'll also take a bit of reading time and learning curve to become proficient in HVAC enough to service your vehicle. Most people opt for having a shop do it. Take your choice of which way to go.

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#8 xtmsports

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Posted 13 September 2009 - 12:04 PM

Sounds as if you're not moving enough air through the condenser when sitting still. One thing to check is your fan clutch. Make sure it is locking up when it should. If you still have the original factory clutch it's probably due for a change. Do you still hear a good roar from underneath the hood when it's hot? Your fan should definitely be locked up and providing max air. You can also see if your ac clutch is disengaging at idle. Take a look at it see if it's turning. If it's not take something and tap the face of the clutch and see if it pulls in. Of course while you're doing this be careful and watch for all the moving parts on the engine. If it pulls in your clutch air gap may be too wide or you may a have weak AC clutch.



I think you are onto something regarding the fan clutch. I have not heard the fan clutch "howling/spinning" on a hot day when taking off from a stand still. I have also noticed that if I am idling in one place for about 5-10 minutes, the engine temp will rise to about 210-220 degrees and continue to rise. So maybe the fan clutch needs replacing.

If that a diffucult task or should I let a tech replace the fan clutch. It doesn't seem like a hard job, but I am not sure if I have the right tools.

Any assistance would be great. Thanks guys.

#9 spurshot

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Posted 13 September 2009 - 01:20 PM

Sounds as if you're not moving enough air through the condenser when sitting still. One thing to check is your fan clutch. Make sure it is locking up when it should. If you still have the original factory clutch it's probably due for a change. Do you still hear a good roar from underneath the hood when it's hot? Your fan should definitely be locked up and providing max air. You can also see if your ac clutch is disengaging at idle. Take a look at it see if it's turning. If it's not take something and tap the face of the clutch and see if it pulls in. Of course while you're doing this be careful and watch for all the moving parts on the engine. If it pulls in your clutch air gap may be too wide or you may a have weak AC clutch.



I think you are onto something regarding the fan clutch. I have not heard the fan clutch "howling/spinning" on a hot day when taking off from a stand still. I have also noticed that if I am idling in one place for about 5-10 minutes, the engine temp will rise to about 210-220 degrees and continue to rise. So maybe the fan clutch needs replacing.

If that a diffucult task or should I let a tech replace the fan clutch. It doesn't seem like a hard job, but I am not sure if I have the right tools.

Any assistance would be great. Thanks guys.



I bought a new fan clutch Friday for the 99 again. This will be the second time I replaced it. (214,000 miles now) I think the factory clutches seem to go about 70-80,000 miles based on my sample of two.

The fan clutch has a 1 7/16" nut on it that threads onto the waterpump shaft. It's a standard (righthand) thread. Remember, "righty-tighty, lefty-loosey"
It's been so long now, I don't recall if the upper fan schroud had to come off or not. Probably easier if it does.

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#10 xtmsports

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Posted 13 September 2009 - 01:28 PM

Sounds as if you're not moving enough air through the condenser when sitting still. One thing to check is your fan clutch. Make sure it is locking up when it should. If you still have the original factory clutch it's probably due for a change. Do you still hear a good roar from underneath the hood when it's hot? Your fan should definitely be locked up and providing max air. You can also see if your ac clutch is disengaging at idle. Take a look at it see if it's turning. If it's not take something and tap the face of the clutch and see if it pulls in. Of course while you're doing this be careful and watch for all the moving parts on the engine. If it pulls in your clutch air gap may be too wide or you may a have weak AC clutch.



I think you are onto something regarding the fan clutch. I have not heard the fan clutch "howling/spinning" on a hot day when taking off from a stand still. I have also noticed that if I am idling in one place for about 5-10 minutes, the engine temp will rise to about 210-220 degrees and continue to rise. So maybe the fan clutch needs replacing.

If that a diffucult task or should I let a tech replace the fan clutch. It doesn't seem like a hard job, but I am not sure if I have the right tools.

Any assistance would be great. Thanks guys.



I bought a new fan clutch Friday for the 99 again. This will be the second time I replaced it. (214,000 miles now) I think the factory clutches seem to go about 70-80,000 miles based on my sample of two.

The fan clutch has a 1 7/16" nut on it that threads onto the waterpump shaft. It's a standard (righthand) thread. Remember, "righty-tighty, lefty-loosey"
It's been so long now, I don't recall if the upper fan schroud had to come off or not. Probably easier if it does.


I read online the procedure to test a fan clutch using a rolled up newspaper to see if it can stop the fan. I tried it and the fan is very strong. The 2001 Tahoe still only has 28,000 miles on it. So I don't think it is a bad fan clutch.

What else could be causing the engine temp to rise to 230 while idling for about 10 minutes and it is about 100 degrees oustide?
Or is this normal? I have a 98 Expedition and when it is 100 outside and i am idling, i have never noticed the temperature rise that high before.

#11 txab

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Posted 13 September 2009 - 01:46 PM

Are the condenser and radiator clear of bugs and debris? Plenty of coolant in the system? No air in the system? Your symptoms still make me lean towards airflow problems. Can you hear the fan vary in speed? If the fan still isn't getting loud at some points, it's not running at max RPMs. You stated it's not as loud as it once was. I'm not trying to convince you that is what the problem is, but don't rule it out completely until you look into some other things

Edited by txab, 13 September 2009 - 05:11 PM.

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#12 spurshot

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Posted 13 September 2009 - 02:17 PM

Could be a sticky thermostat that is only openning part way. Coolant level good? The clutch I bought this time is a Hayden. I've been using factory clutches until now. I went on their web page and found that a 2744 fits my 99 and is for "heavy duty". $59 at Kragen vs the $145 or so I paid for a factory clutch.

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#13 xtmsports

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Posted 13 September 2009 - 06:42 PM

Could be a sticky thermostat that is only openning part way. Coolant level good? The clutch I bought this time is a Hayden. I've been using factory clutches until now. I went on their web page and found that a 2744 fits my 99 and is for "heavy duty". $59 at Kragen vs the $145 or so I paid for a factory clutch.



The issue has been fixed. It turned out that it WAS the fan clutch. Engine doesn't get to 230 degrees anymore and the AC is blowing cold while idling.

Thanks for all of your input/help. I hope somebody else who has a similar problem can benefit from my learning curve :thumbs:

#14 spurshot

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Posted 13 September 2009 - 07:40 PM

Great! Glad your problem is solved. Did you put a Hayden or factory part on?

I just installed the Hayden clutch. Took about 1/2 hr with cleanup and all. I haven't driven it yet. Later tonight or tomorrow I'll know the results.

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#15 txab

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Posted 13 September 2009 - 09:39 PM

Could be a sticky thermostat that is only openning part way. Coolant level good? The clutch I bought this time is a Hayden. I've been using factory clutches until now. I went on their web page and found that a 2744 fits my 99 and is for "heavy duty". $59 at Kragen vs the $145 or so I paid for a factory clutch.



The issue has been fixed. It turned out that it WAS the fan clutch. Engine doesn't get to 230 degrees anymore and the AC is blowing cold while idling.

Thanks for all of your input/help. I hope somebody else who has a similar problem can benefit from my learning curve :thumbs:



I'm glad you got it fixed. Everything you described pointed you to an airflow problem. Thank goodness you didnt' go the route someone else suggested and dump your A/C refrigerant and re-charge. :lol:

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