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Discussion Starter #1
I have a 2010 STS 3.6L V6, I had the compressor and condenser replaced, also the vent door actuator replaced as well.

The AC runs great, and for no reason will start blowing warm air. The air flow is still very good. It appears the compressor clutch is engaging and disengaging properly.

At my wit's end. I love this car. I am the original owner and it has been well maintained. 92k miles.

Any ideas?
 

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Cadillac CT6 (2019)
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2,296 Posts
I had an Olds Bravada that did similar; my case, it happened to be the ambient air sensor telling the system that it was colder than actual temperature (telling it not to cool).
 

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2006 Cadillac STS-4 1SG V8 PREM PERF V8
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11 Posts
How long does it run cold for before it gets warm
Does it have rear hvac if so do the both get cold /warm at e same time
Have you any pressure guages ?
The high and low sides will give some distinct information required to pin point the problem
If you have front and rear hvac and they get warm at the same time then I'd be looking at the compressor clutch or too much system oil
If one is cold and one is warm I'd be looking at your txv in the dash.
compressors with a weak cloth will rotate until system pressure is great enough the worn clutch can't hold it even tho it looks like it's spinning enough to exchange heat effectively
And finally if he car is over full with pag oil the oil will condense in he condenser .. them gets trapped there. This cause the refrigerant to not Stay gaseous and not cool enough to transfer heat so when that happens you will see high system low side pressure and warm air because you can't evaporate gas into gas
 

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Discussion Starter #5
So far, the AC on occasion will run for days no problem. Then a day where it runs for almost the entire day then gets warm. Once and a while it will run for a few miles then start warming up. I may stop and turn off the car and the AC is cold again.
The air always blows well.
My son in law was a Cadillac mechanic a few years back, but didn't work on AC. So we are doing one thing at a time.
The low and high side pressure are fine, I had them checked.
The compressor is running even when the ac is running hot.
I will show my son in law your message.

Thank you
 

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Discussion Starter #6
I thought the ambient sensor work,. But no such luck. Started to get warm again today. Same as before.

Any other suggestions would be appreciated.

Thank you
 

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2006 STS V8 AWD, '95 Ford Ranger
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29,005 Posts
Check the HVAC system for codes with a TECHII.
 

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08 STS 1SG HUD ACC F55 AWD, 08 STS 1SG Platinum HUD ACC F55 RWD
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438 Posts
The Tech II is the original GM test equipment which gives much more detailed information about your car than most OBD 2 readers. With the Tech II you can even test switches, turn on and off engine fan speeds, set engine rpm, variable cam advance, replace computer modules that are vin locked to your car - and many other things. Most if not all other OBD 2s cannot compare to the information and abilities of the Tech II. There is variation between various OBD2s so I cannot tell you if yours is "good enough".
 

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Discussion Starter #10
Looks like we narrowed it down to the fan. The compressor is running, but not blowing cold until the fan comes on. The fan just comes on when it feels like it. It can be running great for days or hours then the vents decide to blow warm, I lift the hood and the fan is off. Then majically a while later it will start to blow cold again and the fan is on.
Going to the dealer to run diagnostics.

Thank you
 

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08 STS 1SG HUD ACC F55 AWD, 08 STS 1SG Platinum HUD ACC F55 RWD
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438 Posts
Find a friend with a TechII by posting your GENERAL location. It can turn on and off your fan to test your theory. Before I spent $$ on a diagnosis, I would replace/swap all of the fan relays and then check the wiring to and from those relays.
 

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Discussion Starter #12
Thank you

If there is someone with a TECHll diagnostic tool in the HOUSTON area, preferably south of Houston. It would greatly appreciated.
 

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07 STS V8 A6 06 GTO M6 (Vengenance Herd)
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72 Posts
Started happening to me one day, discovered one of my fans were dead and not cooling properly. Replaced fan, blowing ice again. Mine did it when stopped and temps begin to rise under the hood. Just a thought.
 
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