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: AC cycling but only in extreme heat

08-09-2010, 06:16 PM
Greetings. AC cycling has been discussed before (that's how I found this forum) but my problem may be a little more specific and I'd like some direction.

I recently inherited a 2002 Malibu LS. I didn't notice any problems with the AC until it's been very warm here. Then the AC cycles on and off for the first half hour of driving. The car sits on a parking lot all day and today the heat index was 109. So the car is hot. The AC blows cold air when it's on but it shuts itself off and automatically comes back on while driving. By "off", I mean that the light on the AC switch goes off and warm air blows from the vents. The blower runs normally throughout the cycling. By the time I get home, it's usually settled down and stays on. There doesn't seem to be any correlation to engine or vehicle speed. Sometimes it will stay on while waiting at a light. Other times it shuts off and on at 60 mph. It appears that once enough (albeit hot) air blows over the engine, something cools down enough and the AC starts working as it's supposed to. Today, I noticed that if the AC light is on, as soon as I press the button to recycle interior air, the AC shuts off for a few seconds then comes back on with the outside air light on. Try to switch it to interior recycled air and the same thing happened again. It did this several times before I gave up and let it do its own thing.

Does this sound familiar to anyone? Is there something in the system that would shut down in extreme heat but then start working again once it's cooled down?


Silver LTZ
08-09-2010, 06:25 PM
I see you have a 2002, but you posted this in the 2008-up section.


08-09-2010, 08:17 PM
Oops. :o Thank you.

08-09-2010, 09:47 PM
Despite the little twist that the recirculation switch seemed to cause a reset, it's probably with the HVAC control head. The switch triggers a solenoid inside the HVAC control head that routes a vacuum to the recirculation door. Either the resulting current draw or vibration caused a portion of the HVAC control head to lose power, including the A/C request circuit. Please see my post in this thread

08-09-2010, 10:29 PM
Either the resulting current draw or vibration caused a portion of the HVAC control head to lose power

Or heat, perhaps? I hadn't thought about how hot the interior is, too. I assumed something under the hood was too hot and was gradually cooling down while driving. But it could also be that something inside the car is too hot. Eventually, the car does get cool enough to be tolerable but that's probably about when the AC starts running normally. I'll definitely look into replacing or cleaning the control head.


08-10-2010, 04:24 AM
Don't overlook the obvious, either. If the refrigerant is underfilled or overfilled it'll cycle, but the dash light won't cycle.

08-10-2010, 05:41 AM
The dash light definitely cycles on and off. I've noticed that the default air circulation setting appears to be outside air when the AC is first turned on. I set it for recirculating inside air because it cools the car down faster. When things start cycling, the AC LED goes off and when it comes back on, it sets itself to outside air. I can't watch the light constantly while driving, but I can tell it's reset itself when I look down to find it's back on outside air even if the AC has come back on.

08-10-2010, 04:16 PM
You are definitely dealing with an electrical issue.