Audi Repair: Audi A6 1.9TDI 2002, pollen filter, auto button

Question
QUESTION: My air-con will not operate, the Econ (switches air-con off/on) light remains off after pressing it. The auto button of the climate control(should also switch air-con back on, also as no effect. There is gas in the system and I've tired removing the pollen filter all no effect? can you offer any advice?

ANSWER: Is there enough pressure to allow the compressor to switch on?  Are the fuses OK?  The switch unit itself can also be a problem, although in 2002 the switch units are better.  Check the pressure switch and fuses first.  Let me know,  Jan

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QUESTION: I do not have access to the equipment to test the correct pressure. All the fuses are ok, checked them first (should have mentioned)I do not know where the pressure switch is or how to test it. I suspect the compressor although this was replaced a few years ago! I was hoping this was a common fault and the Econ staying on was to protect the system or would have indicated a particular fault - guess I'll have to take it in - thanks for taking the time to respond.

Answer
No problem. The pressure switch will allow the compressor to switch on, notmally it goes to 0 Ohm when the pressure is OK.  It could still be the compressor also, or the clutch on the compressor.  Does the compressor turn freely (without engine running?)

Let me know,  Jan