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I bought a 2008 G6 GT Coupe about 3 months ago it has 36000 on it, it has been in the shop twice now due to the climate control randomly going out. I lose all power to the system, normally it does turn back on. The a/c expansion valve has been replaced and HVAC Control Head Module has been replaced. Anyone got any ideas?.....the dealership is at a loss and so am I.
 

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I bought a 2008 G6 GT Coupe about 3 months ago it has 36000 on it, it has been in the shop twice now due to the climate control randomly going out. I lose all power to the system, normally it does turn back on. The a/c expansion valve has been replaced and HVAC Control Head Module has been replaced. Anyone got any ideas?.....the dealership is at a loss and so am I.
Auto or manual HVAC? Do you have remote start? Under what circumstances does it "turn back on"? How have you actually verified that you "lose all power to the system"? HVAC has several sources of B+ power.
 

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Manual, Yes on Remote Start, It randomly turns back on just as randomly as it turns off. The buttons and the blower everything shuts off, no lights no power
 

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Manual, Yes on Remote Start, It randomly turns back on just as randomly as it turns off. The buttons and the blower everything shuts off, no lights no power
Either the HVAC controller power supply or it's ground is intermittent. Sounds like it's just out of warranty. Have you tried another dealer? Should be able to resolve this under the bumper to bumper. I'll try to look at the power & ground schematic tonight.
 

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Usually the first place to start with intermittents is with the relays in the circuit.

But just for fun, with the ignition OFF, swap out fuse (actually a fusible element) #19 (30 amp, pink) under the hood with another one of the 30 amp-ers & see it anything changes. You may note that if you pull fuse 19 you will kill all power to the HVAC head unit.

If no joy, swap out the HVAC BLOWER HIGH RELAY in the cab fuse box. There is an identical relay in the engine fuse box you can swap in.

There is also a HVAC Run Relay that's internal to the BCM that would require swapping out the BCM to change. (Why they did that I don't know).
 

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Thanks for all the advice everyone....looks like the computer was bad, turns out it was doing a lot of other weird stuff I didn't even realize, the dealership replaced it and so far so good
 

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I have a 2007 pontiac g6 hardtop convertible my a/c or heat won't work at all and only 1 light on the heat a/c control comes on if that any help anyone
 
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