Air conditioner not working properly

BOB CRIST

MEMBER
2008 GMC ENVOY
4.2L
6 CYL
4WD
AUTOMATIC
155,000 MILES

When I shut the A/C off and then turn it back on (the light on the switch does come on). It won't engage the compressor until I shut off the ignition, disconnect the battery a couple seconds and reconnect the battery, restart the engine and switch the A/C back on. Also sometimes while driving, it quits cooling, the A/C must cycle off (the light on the switch is still on) and won't cool until I do the disconnect and reconnect battery procedure. (The light on the switch comes on, but no cooling happens unless i've performed the battery disconnect and reconnect procedure). Could this be the relay not resetting? I have not changed the relay. Help!

4 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

Since it is resetting when you disconnect the battery, I recommend having the can-bus system scanned. CAN stands for controller area network. Basically, all the modules/computers are tied together via a few wires. When you scan the CAN, it will provide diagnostic trouble codes regardless of the module/computer storing it.

Here is a video showing how it's done:

https://youtu.be/InIlnsjOVFA

I recommend starting here because there could be a few different things causing this. For example, a faulty relay, low or high-pressure switch, Freon level, a wiring/connection issue, and so on. When there are multiple different possibilities, it becomes a guessing gas as to where to start testing.

Let me know if that is something you can have done. If you do, let me know the code that is found so I can better direct you.

Take care,

Joe

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Thursday, August 26th, 2021 AT 10:07 PM

BOB CRIST

MEMBER
4 POSTS

Joe, upon your advice, I checked the Freon and indeed it was low. I added about 3/4 can and it's blowing colder than it had been. I'll let you know how it works over time. The symptoms didn't seem to be as the would have been on the older units I've had experience with. '08 is pretty modern for a 66 year old man I guess. Thank you so much.
BOB.

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Thursday, September 2nd, 2021 AT 5:21 PM

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi Bob,

First, you are very welcome. I'm just glad it helped. And an 08 is modern for me as well. LOL But my 78 is still my favorite. Very little to go wrong.

You take care of yourself. Also, please feel free to come back anytime in the future if you have questions. You're always welcome here.

Joe

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Thursday, September 2nd, 2021 AT 6:58 PM

BOB CRIST