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2002 gmc envoy_slt
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Discussion Starter · #1 ·
I have read several of the threads, but they don't seem to help much. I have an 2002 Envoy SLT with 100k. Fan clutch replaced at 35K running fine. Water pump replaced at 95K, no a/c service as of yet.
On the highway at 70mph the ac is blowing cold air (time varies) usually 20 minutes and then it will then stop blowing cold (blows warm air from 5 minutes to 20) and it will then cycle back on. And by cold air i mean you would have to eventually put a sweater on if it didn't cycle off. When it blows warm air it feels about like the ambient temperature outside which has typically been in the 82 - 87 degrees range.
I do not know if this is low pressure in the system itself (which is self contained and should not leak and if it does leak would the air be that cold?) or if the low pressure cycling switch is the culprit or is it something completely different.
 

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2003 gmc envoy_slt
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357 Posts
You need a new A/C low pressure cycling switch. Cheap and easy to replace without having to open the system. Do a search above and you will find plenty of info including a picture of where it is located.

C.B.

P.S. I tried to find the picture I recall being on here and couldn't but the switch screws into the a/c accumulator, the big silver cylinder in the a/c system. The most useful post I found using search is "a/c shuts off when hot outside" dated 5/20/07. Good luck.
 

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2009 chevy
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6,431 Posts
The SLT uses the auto HVAC. Set a temp and the internal thermostats will try to maintain the set cabin temp.

The "problem" you describe, may be normal.
If there is a problem, it may be with a temp sensor, or, there may be a problem with the ac components.


bluemarblez2, welcome to the site, you will find a lot of info about your vehicle and a lot of people that are willing to advise. But, most of us don't like to search through the post to find the vehicle information. Please take some time to fill out the vehicle info on your profile. You will find it under the User CP pull down.
 

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2002 gmc envoy_slt
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14 Posts
Discussion Starter · #4 ·
Thanks for the advice. I filled out the CP.
I will replace the pressure cycling switch since it's inexpensive and see if there is any improvement.
Could be an internal sensor. I have temp set to 60 degrees and I know it's not that cold in the cabin when the AC cycles off.
 

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2003 gmc envoy_slt
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30 Posts
I think I have the same issue with my 2003 SLT.

My AC blows very cold! but every few mins or so I loose that crisp cool air.
The outside temp can be 85, I turn the AC down to 64' and this still happens.

Does this sound like the low pressure switch and is there anything I can do to diagnose what is happening?

Thanks!
 

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2002 gmc envoy_slt
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547 Posts
I had the exact same problem on my 2002 SLT with 149K miles. After replacing the low pressure/cycling switch, and adding/confirming correct low side pressure with no improvement I gave up and took it to the dealer. I had read about a software update that addressed this problem while researching this subject on this awesome TrailVoy forum. Sure enough, dealer found no mechanical problems with my AC system. Re-Flashed the BDM with the new parameters and the darn thing runs COLD all the time now! SWEET! Also, fixed the wandering side view mirrors with the same download. Dealer charged $120.00 The best $120 I've spent lately. HTH c good
 

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2002 gmc envoy_slt
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14 Posts
Discussion Starter · #11 ·
There used to be; I could not find it either.

Its right next to the coolant reservoir its silver has an octogon shape (so passenger side up top by the firewall). there is a wire running into the recycling switch also called an actuator i think. Unplug the wires (its just one plug) running into the switch (its plastic and sticks out about 2-3 inches). Then the switch itself is simply unscrewed from the silver octogon (i have no idea the name of this part).

Screw in the new switch, plug the wires back in and your done. It will take you about 5 minutes. Hope this helps.
 

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2002 gmc envoy_slt
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Discussion Starter · #13 ·
Yes, sorry should have mentioned that, it can be replaced without any loss of refrigerant.
Believe i got mine from autozone. I don't remember what the part number is but it was under ac and was listed as an actuator of some sort. Sorry I am not more help in that department. Call the parts store they will tell you what part you need. There were different prices from 12.99 to 32. Check around.
 

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2002 gmc envoy_slt
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Discussion Starter · #15 ·
I don't know where the receipt is, but one of the major chains has the part for 12.99. I thought it was Autozone but i am not sure. I know it's not Oreilly or Napa and I don't think it was Advance Auto but it could have been.
 

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2002 chevy trailblazer_ltz
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Autozone has it.

The Clutch cycling pressure switch is a tiny little thing attached to the receiver dryer (That thing that looks like a big aluminum can on the passenger side under the hood.) It will be screwed onto the back with a small wire harness.

Autozone carries the part:

It is Part bumber ( MT0968 )

Once you buy it, it will make sense where and how it should go in. You just screw it on and reattach the wire harness... should take no more than a minute.
 

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2003 Chevrolet Trailblazer LT EXT
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473 Posts
A/C blows cold-warm-cold again

Great advice. I also had cold-warm-cold again A/c and replaced the compressor cycle switch. First I was a little nervous about removing the switch in case the refrigerant escaped, but after reading the threads I felt assured that it was OK to spin it off and replace. Surprise...no problems and now my A/C is back to blowing cold.
Thanks to everyone for posting their experiences and technical advice.
 

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2002 chevy trailblazer_ls
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25 Posts
Hi,
I know this thread is old, but in all my searches I haven't seen how to test the switch. I don't wanna spend $32 (or however much it costs now in 2017) without confirming that the switch is bad.
Does anyone know how to test the switch? Thanks
 

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2008 chevy trailblazer_ls
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1 Posts
2008 Trailblazer Temp Sensor

My temp gauge bottoms out and the temp warning light comes on. The air conditioner stops working. After a while the gauge will return to normal and the warning light goes out and the air blows cold. The truck does not appear to be running hot at all. After having codes checked at O'Reilly's it indicated it was either the coolant sensor or the thermostat. Since the truck didn't get hot the likely cause was the sensor. After finally finding the sensor (which is on the passenger side close to the firewall) and replacing it (which was no easy task!) the light came on again!! I know the gauge and air problem is related because it never happens any other time. The last option I can think of is the thermostat, even though it doesn't sound reasonable. Any other thoughts?
 
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