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Discussion Starter #1
2009 Pontiac G6 GT Coupe

This has been going on for well over a year. My AC stopped working over time (I noticed the temps were getting warmer and warmer)

I took it to a mechanic to fix and was told the problem was because a hose was hooked up improperly by the previous mechanic who installed my replacement engine (thanks warranty)

Everything worked great. Few days later it's back to blowing hot air.

I left it, and dealt with it for a few months. Then my car overheats. I take it to a new mechanic, there's a t-hose leak causing coolant to leak out. They fix it, replace my coolant, etc. My AC works perfect, better than it ever has... for two days.

Once again it's back to blowing hot air. I'm getting tired of it. I live in an area where even a 10 minute drive results in me sweating, windows down and all.

Does anyone have any idea what it could be? I'd greatly appreciate it
 

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Discussion Starter #2
Forgot to add that OBD-II code P0420 is constantly displayed. Even when clearing codes, it comes right back after next startup.
 

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Some thoughts on this. Is the compressor engaged when you're getting hot air out?

Could you have a malfunctioning hot/cold blend door actuator that's causing the heater to cancel out the A/C?

The P0420 is unrelated. IIRC, it has to do with the evaporative recovery system.

Doug

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Some thoughts on this. Is the compressor engaged when you're getting hot air out?

Could you have a malfunctioning hot/cold blend door actuator that's causing the heater to cancel out the A/C?

The P0420 is unrelated. IIRC, it has to do with the evaporative recovery system.

Doug

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Thanks for the reply. Excuse my ignorance but I’m not very knowledgeable on this stuff myself. What would I be looking for to figure out if the compressor is engaged and if the actuator is malfunctioning?

Thanks
 

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Thanks for the reply. Excuse my ignorance but I’m not very knowledgeable on this stuff myself. What would I be looking for to figure out if the compressor is engaged [?]
With the hood up and the A/C on, you should be able to see the clutch engage and disengage on the compressor. When it's disengaged, the belt is turning the wheel on the compressor, but the center section of the wheel is not turning. When the A/C is turned on, the clutch should engage which causes the center section to turn with the wheel.

...and if the actuator is malfunctioning?
For this, you need to turn the engine off but key on. It helps to turn the radio off, too. If you move the hot/cold blend knob, if you listen very carefully, you should hear the actuator moving the blend door.

Another test for this is, with the engine running and up to temp, turn on the heater, feel the hot air coming out of the vent, then move the temp selector to cold, and see if the air temp changes. If it stays hot, the actuator is stuck/not working.

In summary, play with the A/C controls. See if you can get cold air blowing by moving the temp selector back and forth, and pushing the A/C button off and on. It could be something as simple as an intermittent relay somewhere that's causing the compressor to not come on. Sometimes, with repeated attempts, it will begin working again, for a while. Ultimately, once it's identified, it can be replaced.

HTH.

Doug

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Thanks for the reply. Excuse my ignorance but I’m not very knowledgeable on this stuff myself. What would I be looking for to figure out if the compressor is engaged [?]
With the hood up and the A/C on, you should be able to see the clutch engage and disengage on the compressor. When it's disengaged, the belt is turning the wheel on the compressor, but the center section of the wheel is not turning. When the A/C is turned on, the clutch should engage which causes the center section to turn with the wheel.

...and if the actuator is malfunctioning?
For this, you need to turn the engine off but key on. It helps to turn the radio off, too. If you move the hot/cold blend knob, if you listen very carefully, you should hear the actuator moving the blend door.

Another test for this is, with the engine running and up to temp, turn on the heater, feel the hot air coming out of the vent, then move the temp selector to cold, and see if the air temp changes. If it stays hot, the actuator is stuck/not working.

In summary, play with the A/C controls. See if you can get cold air blowing by moving the temp selector back and forth, and pushing the A/C button off and on. It could be something as simple as an intermittent relay somewhere that's causing the compressor to not come on. Sometimes, with repeated attempts, it will begin working again, for a while. Ultimately, once it's identified, it can be replaced.

HTH.

Doug

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So I tested both of the things you said. For the temperature dial, from hot to cold with the AC turned on, there definitely is a difference in temperature... however cold is still not cold. It’s outdoors temperature at best. Heat works as normal though.

The compressor does not seem to be spinning in the center. All of the belts are turning but the compressor does not seem to be engaging as you said.

Does this mean a new compressor is required or is my current one fixable?
 

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Edit to my last post... I might be wrong about the compressor. To be honest I’m not sure what I’m supposed to be looking at. The manual doesn’t show any pics and I can’t find any pics of it online for my specific car. So I might’ve been looking in the wrong location
 

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Sorry for triple posting... is there not an edit function?

Final update, I’m 99% sure I found the compressor and it does not spin or engage or anything from what I can see with the AC on or off
 

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Sorry for triple posting... is there not an edit function?

Final update, I’m 99% sure I found the compressor and it does not spin or engage or anything from what I can see with the AC on or off
There is a pressure switch in the A/C lines that controls the compressor clutch. If the pressure is too low (due to low freon) it won't engage. Besides low pressure, the wires to the switch can also cause this. Or a bad relay for the clutch, which I think is in the underhood fuse block.

Sorry, I don't have my G6 anymore, so I can only go by memory.

Since you noticed a good change in behavior after the engine work was done, I suspect a bad wiring connection. Maybe the wires god jostled which helped close a connection that made it work.

At this point, you can try tracing the wires from the compressor, and from the pressure switch. Inspect the connectors in the paths. Make sure the wires are not frayed or hanging by a thread. Disconnect and re-connect the connectors to be sure they are fully seated.

If it's not wiring or a relay, the next step would be to get some gauges and check the freon.

HTH.

Doug

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It definitely sounds more like a freon problem but in recent discovery after I got my g6 I had to replace the radiator due to a wreck in the process it had overheated. I was always told when a vehicle overheats you should change the thermostat as well I want against my better judgment and did not. Everything seemed fine until one day I was driving to work and it wasn’t blowing cold I found it odd because the day before I charged it myself and it was blowing perfectly. Out of habit I checked my gages and noticed my thermostat was reading 0° I thought that was crazy cause my car was on the road for 15-20 minutes before I looked, my thoughts on that, old coolant will cause your thermostat to be off causing it to overheat and or not get to the correct temperature. But there was no way it could’ve been coolant because I replaced the radiator and all new coolant the correct coolant the week prior So I asked one of the technicians I work with and he thought it was strange but couldn’t give me any answers on my way home I left work and got on it and kept on it trying to get the motor hot as possible apparently the thermostat wasn’t reading which made the vehicle go into that safe mode which cause the AC to stop working and fans to kick on I was able to get my thermostat to work by getting super hot water going through it on the way to replace the thermostat I replaced it and I haven’t had an issue since
Maybe you can make sure your car thermostat is reading correctly also you can unplug your high Pressure side on the a/c and take a paperclip and bypass it to see if the compressor kicks on “only for a few minutes this can cause more damage over time” You’re only jumping it just to make sure that the compressor is functioning after jumping it and it doesn’t work that means you have a bad compressor. If it does come on you need R-134a and if you are not familiar with cars and how to charge an ac bring it to someone.
 
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