Klima, I have been told, tells computer compressor clutch is spinning and the engine is running. i.e. is clutch stops due to seized compressor, with the engine running, the computer declutches to keep the single serp belt from burning up ... appears this was to prevent loss of end state driveability with the move to the newer serp belts (older models had two belts, if I recall).
Klima can be bought rebuilt for about $50 or so, I think.
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg