I've checked engine RPM and compressor RPM with a DVM set to AC volts. I grounded the other tester wire for compressor test. I don't remember the values but they vary linearly with rpm.

There's an intermittent fault in my car so I have an ice cube relay in place of the Klima. The ice cube relay closes a switch between 5 and 7 based on a ground signal from 10. I don't know if the fault is in the Klima or upstream. Seems to be temp dependent in that it never happens when it's cool out (go figure). Once it cuts out, it won't come back on until and engine restart. I had the Klima innards resoldered but that didn't fix it. FWIW, the tach always works.

Brian, you're exactly right.

Keith, I don't know if the more complex EDS in a 95 means the Klima does more or less than an 87 Klima.

Sixto
95 S420
87 300SDL

Thanks.

Just to clarify: The control unit will leave socket #10 open until it calls for a/c, and then it will ground #10 signaling the Klima to close if all other parameters are met?? Therefore, there is never any voltage on #10 at any time??

I don't know if there's voltage at 10 when there's no signal. I'm pretty sure it's not an active 12V signal to disengage the compressor.

For more on the ice cube relay, given the common Bosch relay pin-outs, 86 and 30 connect to Klima socket 5, 85 connects to Klima socket 10, and 87 connects to Klima socket 7.

I used regular bullet connectors and spread the contact for a snug fit in the Klima socket holes.

What I'd like to do is leave the Klima in place and wire a switched ice cube relay in parallel. Also have a dash warning light to tell me when the PBU says the compressor should be engaged but it isn't. All this effort to avoid buying a working Klima relay

Sixto
95 S420
87 300SDL

Attached Thumbnails