I have a 2009 Pontiac g6 GXP sedan with the 3.6 VVT engine, 199k miles and automatic. Located in mid TN.
My question pertains to the a/c and heat system. When I start my car and turn the heat on like today when it was 33 degrees outside it doesn’t come on. This is from a cold start so I know obviously it takes time to warm up but that’s not the issue. The issue is it sounds like a door pops open or closed while driving down the road and then the heat kicks on but it’s full on. I have the automatic temperature system and when I change the temp it doesn’t change the temperature of the heat. If I turn it off and turn it back on within 10-15 of turning it off it does the same thing. Blows cold for a time period between 1 minute or could be an hour later then door pops open or closed then heats back on. I’ve replaced the blend door actuator (under dash on drivers side) and no change. I have the actuator for the passenger side that controls the recirculating air, and the main control unit but have not replaced those yet. Any help or ideas would be great appreciated.
I’ve replaced the blend door actuator
sometimes these parts need to be calibrated with a good diagnostic tool before they will function properly
Your body control module may be starting to act up. GM products' electrical components don't age very well, especially not with 200k miles on it.
I had a somewhat similar issue with a 1994 BMW 540i. The air conditioner worked fine, but you could only get heat when you'd select the windshield defroster. I just lived with it. It wasn't worth tearing half of that car apart in order to fix.
If you have a vaccum-actuated system, you may have a vacuum leak somewhere. My 1999 Ranger's air conditioner sometimes stops blowing cold air into the cabin at certain throttle positions. It's annoying, but I deal with it because of the same thing. Heat works fine, and always has. If you have a good maintenance manual, find out whether or not your heat and A/C systems are controlled by engine vacuum. Any leaks will cause issues.
If you have a vacuum-actuated system, and your vacuum hoses are original to the car, you might want to consider replacing them all. They're 15 years old and rubber dry rot over time, especially undergoing near-constant hot and cold cycles.
@justin-shepherd, Update I’ve replaced the module and while the plastics were removed I plugged everything back up and ran the car to warm up. After warm up I ran thru the cycles. All buttons work, actuators seem to be working properly, fan works as it should and I could physically see the door moving that was working In Conjunction with my going thru the vent location from defrost to face, or floor. The only conclusion I can come to with it is the blend door itself is broken.