I'm again/still stumped at trying to read the OBD codes on my 92 400E. Unlike the CD, the car does not have a pushbutton or an LED to read them. The big computer box in the back corner of the passenger side of the engine compartment has a circular cap (like an oil fill cap) covering a single round 38-pin connector.

Can anyone fill me in on how to read my codes?

I'm trying to troubleshoot an air conditioning system that will not turn on the compressor. I had it in to an AC place, and they verified the pressures, the pressure switches, and that the compressor could be jumpered to make it come on, when it would cool things properly.

It looks like the system is not telling it to come on, and I would like to know why not! Any leads on how, short of taking it to the local stealership? (I will if I gotta, but I ain't gonna like it!)

Thanks, guys!
Gerry Visel