I STFA and couldn't find a clear answer on this so here goes:

My external temp sensor is shot. The dash display reads anywhere from -40 to 115 degrees at random. My A/C is intermittently blowing hot air. No real pattern to it, but I notice that sometimes the temp sensor is under 40 degrees when this happens (sometimes it's not).

I read that there is an intake temp sensor for the HVAC, a cabin temp sensor, and the temp sensor in the front bumper for outside air temp. I know the sensor at the front bumper is bad, possibly one other as well which I think may be causing the problem. Dealership parts guy is telling is telling me that the bumper sensor & cabin sensor are what is read by climate control unit (& could not confirm intake plenum sensor even exists). Others have said intake plenum temp sensor & cabin sensor are tied to the climate control. I have a few questions:

1) What sensor(s) are used by the climate control to determine output air temp?

2) Any suggestions to connecting my VAG to the Climate Control unit - I have not been able to successfully connect to that module (other modules are no problem) in order to read the outputs for the temp sensors. Would a battery disconnect make any difference?

3) I have 2 Part numbers:
8D0907539 - Dash Cabin Temp Sensor
4D0820539 - Front Bumper Temp Sensor
Anyone know the P/N for the sensor inthe HVAC intake plenum?

 

8D0907539 - SUNLOAD SENSOR/DASH TEMP SENSOR (this is the one that sits in the middle of your dash)

8D0820535 - outside temp sensor (the one in froint of the radiator)

4A0820539 or 4D0820539 - Inside temp sensor in plenum.

Check with the parts guys first.

You might also want to check with 1stVWParts.com, they are always cheaper for OEM than your local dealer.