Heat-A/C problem
 

I have a problem with the climate control in my 2001 boxster base convertible, manual transmission. The system behaves as follows:

If i hit "auto" I get full blast A/C, highest fan speed, even with temp set to 85, but can turn fan speed down. Temp control has no effect, except...
If I manually set temp to "HI" I get full bore heat, but can turn fan speed down
I must manually shut off A/C, or it is always on.
Fan seems to work at all speeds by manually dialing in desired speed, but never changes in Auto, always full bore A/C. If I turn down fan speed, auto shuts off and display reads "Manuell"

I have changed cabin temp sensor with a used one that was claimed to be good but I had not tested. Any ideas?

I have something similar with mine. Have you done the diagnostics on the AC head unit. I had concluded that the sensor was probably faulty as the diagnostics showed the internal temperature reading to be way over what it actually was.

The net effect for me is that on auto I get full blast cold unless I set temp to Hi.