Yesterday I did a thorough cooling system cleaning on my 84 300SD; during a thirty minute idle I noticed that the AC compressor clutch was engaged - with the CCU OFF button pressed in. I then unplugged the compressor coil connector until I could do some testing today.

The AC has been a NO-OP as the PO lost the freon via a failed O-ring at the expansion valve; the R4 compressor fortunately hasn't seized but I've now been wondering just how much oil is left in it and whether it's still capable of compressing refrigerant gas into a liquid.

Today I checked for voltage at the compressor connector and found the following: (CCU still has the OFF button latched.)

1) with key at positions 0 and 1 - no voltage.

2) with key at position 2, I found 12 volts at the connector.

I previously searched here for threads using keyword KLIMA and found much good information. I have looked under the hood for the KLIMA using the P/N 001.545.74.05 but haven't found it. (The box with 001.545.9832 on it is the glow plug controller judging from the wiring that's plugged to it.)

From reading threads I'm thinking that one of the two relays soldered to the KLIMA board has its contact points (or is it solid-state?) for the compressor clutch coil's 12 volt feed seized closed.

Can anyone advise where the KLIMA is located on an 84 300SD? Also, is it in the same location on an 82 300SD?

Thanks for any info on this.

__________________
Respect, protect, and maintain complex systems - whether natural or of German design, to benefit from their full potential.

1982 300SD W126.120 with an OM617.950 from a W116.120
1984 300SD W126.120 with an OM617.951