I have finally resolved my loss of tachometer and A/C compressor function!

Initial loss of both functions at the same time started last year and usually a couple of whacks to the Klima relay would restore full function. The Klima on my 126 (91 350SDL) is located on passenger side next to and sharing a plastic socket block with the ASD module. Fastened to the side of it, but completely separate is a two 10A fuze OVP.

After tracing every darn wire and cleaning every connection (including relay pins and sockets) in the engine compartment over a period of two nights, I gave up and decided to put off taking the wiper motor transmission tray apart (necessary to get at the back of the socket block to check for poor connections/shorts) till the weekend. After a few emails from a couple of really great guys (Steve and Marshall) I decided to take a very careful look at the OVP (had previously checked the fuzes).

After reading comments by Beatle Juice, G-Benz, and Mick J plus an incredibly informative dialogue via email with Steve Brotherton and Marshall Booth, I removed the OVP and examined it ... looked OK on outside .... BUT, it appeared to RATTLE a bit ... hmmmm. Pried apart and found two brackets that hold points assemblies were no longer soldered to the board. Even more astounding, a very small spring that tensions one of the sets of points was rolling around inside .... voila!!!

Carefully reinstalled the spring, clamped the brackets to the board while I resoldered them back in place - resoldered everything else just for grins! Immediately got tach function back, but still had no A/C compressor. Swapped original Klima for the used I got and both now work 4.0!

This could have been a two failure problem, but I think I had likely damaged the original Klima as I resoldered it several times and, well, embarrassingly, probably beat on it a bit too much (only after receiving the new (used) one.

Thanks again to Steve, Marshall, Beatle Juice, G-Benz, and Mick J!

If only I could figure out why that ASD light stays on .... got a feeling it hydraulic issue, not electrical!

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George Stephenson
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