AC sometimes blows hot air

Tiny
GUGOO
  • MEMBER
  • 2005 AUDI A6
  • 2.0L
  • 4WD
  • AUTOMATIC
  • 100,000 MILES
The fuse diagram indicates that the AC, the heater and the blower are all on one 30 amp fuse. How can one disconnect the AC system without effecting the hot air system? Can one simply disconnect the terminals to the compressor?

The problem is that the AC system works erratically sometimes blowing hot air.
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Friday, October 20th, 2017 AT 6:48 AM

1 Reply

Tiny
STEVE W.
  • MECHANIC
  • 12,789 POSTS
That issue would not be the compressor, it would be that you have a blend/temperature actuator in the heating system that is starting to fail.
Those actuators move doors inside the HVAC system that send air through the heater core or through the AC core (or both if you are on defrost) to give you the interior temperature you requested.
When they start to fail they will start routing the air wrong and you get cold air when you want heat, or heat when you want AC.
The other common failure if you have the system that is split so the passenger gets different temperature air is the interior temperature sensor, then you get odd air temperatures because the computer cannot tell what the actual temperature is.
However, if it is only one side with an issue it is more likely the blend/temperature actuator itself.

There is a TSB that might cover your problem. It relates to a guide pin on the actuator coming apart. To check this you remove the panel above the drivers side foot well and you can see the actuator. The pictures show the bad and good position for that pin.
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Friday, October 20th, 2017 AT 9:57 PM

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