caseyjay

Hello, I just bought an Q7 '07 4.2FSI and seller told me AC "probably just needed regassing". The service center (here in Europe) took about 30mns for the job (a lot less than I am used to for a good vacuum) but showed me the ECON light was stuck on and could not clear the fault codes. With help from VCDS I found a faulty flap motor was preventing Basic Settings adaptation, now the ECON light is off, but no cold air.

AC gauges show 55psi static which is a bit low for my ambient temp (should be near 80) but I guess there is a charge (I expect the service center did not check this was the quad-zone climatronic with 2 evaporators and needs more charge). On AC start, no change on gauges, no noise so reckon Compressor (clutchless) is not engaging.

VCDS shows compressor state on/off, N280 valve getting load albeit low, AC pressure in line with gauges so I don't suspect a sensor fault.
However, fans do not come on with AC. Output test from Engine module works ok and they are running to cool engine rad. But I see a ZERO value in Fan Request from AC and the AC output tests for fans do not respond.

If this is like my BMW X5, any aux fan fault will prevent AC from running but not trigger a fault code? Am I on to something?

And is this possibly the Climate Head Unit (J255, in dash) or the Fan Control unit (J293, on the fan itself). Is a used climate unit safe or are they known to have issues? thx for any advice