Compressor shuts off - ETR switch
 

I have been studying the wiring diagrams for my car (1978 300D) and it appears that the A/C clutch is connected to the pressure switch which is connected to the ETR switch. My compressor cycles off and on at high rpms way too much, so the air never gets very cool. At high rpms, sight glass is mostly clear, with some small, fine bubbles. The drier and pressure switch on the drier are new - can you check the ETR switch somehow? I can not find a procedure for checking it in the manual??

Could something else be shutting off the compressor? I can easily replace the ETR switch (about $42).

Ryan

Is this the part your considering replacing? If so you can jump the wires together that go to it and see if the a/c gets cold enough.
The purpose of that switch is to prevent the evaporator from freezing up. I have seen them fail in exactly the manner you describe.

Yes, that's it.

ryan

I disconnected the ETR switch tonight and jumped the wires with a paper clip and drove around town for a few minutes. Vent temps reached as low as 38 degrees in no time! I am going to replace the ETR switch as soon as I can!

Thanks,

Ryan