Strange climate control unit problem...
 

Hi guys,
In the midst of trying to get my AC to work in the 300e, I've stumbled on an odd problem. I can't get the climate control panel to send a turn on signal to the Klima relay and on to the compressor. I've tested the relay, when battery voltage is applied to it, it kicks on the compressor, blows nice and cold. I've tested the temp sensors that input to the climate control panel, all appear good per MB's specs. And I've thus far put in three different, albeit used climate control panels, all work fine in all different functions, but none will send a voltage signal to the Klima relay. I'm completely stumped, any ideas?

Thanks!
Scott

The a/c controller sends a ground signal to pin #10 of the Klima relay.

ON a 1987 car the most likely problem is the exap temp sensor.