AC clutch wont engage. There is no freon in the system (just got done flushing it and replacing expansion valve and reciever drier and resealing everything) but im just trying to get the ac clutch to engage without the car running so I can atleast know the clutch works. I jumped the pressure switch with the car in the on position and get 0 volts to the clutch. Sporadically i will get some voltage but still not enough to engage the clutch.



The AC failed prior because the compressor seized. I tried replacing the climate control unit (buttons) and the fuse is fine since the blower works. What else is there to fail? I understand the 85's had a klima relay. Can this be my problem?

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1981 300SD 512k OM603

The Klima is an additional relay between the CCU and the clutch. On the '85, the first year of the Klima, it gets some signals from maximum throttle position and IIRC, the engine temperature, and will drop the clutch if certain parameters are not met.

If the Klima fails, the clutch cannot engage.