I have a non-diesel related question about my 190D I just acquired. The AC blows cold, and its nice. The weird thing is that the compressor clutch never disengages. The only thing I could do to turn it off was pull the harness off the compressor. unplugging the pressure switch had no affect. Anyone come across this? or have some good diagnostic info I can look at? Im pretty good at figuring out these little electrical things, but haven't been able to find the info I need. Thank You!

Send a PM to VStech he knows this stuff cold......no pun intended......

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'89 260e (212K Mi.), '92 400e (208K Mi.), '92 400e (not a misprint) (146K Mi.), '95 C220, '81 240D--Sold

There is a short in the wiring that is giving power to the compressor

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1990 190E 3.0L

So I found a switch that the PO put in to short the Klima relay and turn on the AC system. Now to figure out why it doesn't turn on my itself. The pressure switch is closed.

Possibly bad relay?

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1990 190E 3.0L

It sounds like the PO installed a switch in order to bypass the Klima relay. I suspect that the Klima relay is defective so the PO just bypassed it. There are times (hot days) when the Klima relay gets overheated and shuts down the compressor. When this happens on my car I pull the Klima relay and wrap a cold wet cloth around it for a few minutes, reinstall it, and everything is fine. A new Klima relay is about $150, but you might get lucky and find a good one from a wrecked car. Your compressor is staying on all the time because the Klima relay has been bypassed by the switch.

Maybe I can swap it with my 92 if its the same. Thanks for the insight!