There should be a pressure switch on the system. It will cut the power if the lines are pressurized properly. I'm not sure where they are on our cars though.
2001 A6 non turbo automatic
Ac compressor clutch has no power when I activate AC
I put direct power to it and it worked fine.
Tested ac clutch relay and all systems are a go
AC button lights up when I press it and you can hear the change over behind the dash.
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