1985 300TD AC Compressor?
 

The AC compressor on my 85 300TD will not engage even though the system is full. I have replaced the fuse in the fuse box, but the compressor still will not come on. Is there another in-line fuse? Any ideas appreciated!

Richard

Won't a bad pressure switch cause this too?

On my SDL, the compressor wouldn't engage due to a bad compressor clutch.

bad RPM sensor, bad klima relay, bad air gap on clutch, etc etc etc... search klima diagnostic

For starters, determine if you have power at the compressor. Then you will know if your problem is electrical or mechanical.

On my car, same year and model, I have to rev the engine to get the compressor to kick in- been that way for years.

Once I do that, it's fine. If I recall, there's a vacuum operated switch on the driver's side inner fenderwell that enters into the mix somewhere.

Of course, this is assuming you have enough refrigerant and good hi- low pressure switches.

Found the problem: the OVP relay had a blown fuse. On the 85, the OVP relay controls the tach and the AC compressor. Maybe on the 84...not sure.