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