ok it started off my tach wasn't working unless you unplugged it then plugged it back in, then it would work for a while (5 mins maximum) then quit, and would never work after shutting down and restarting. so I found the "cigarette butt fix" threads and promptly pulled my tach amp and removed it from the screw on housing, which wasn't a simple task, but with some twisting and wiggling it finally came loose. not being a smoker myself I folded up a piece of paper (I think 6 folds) then trimmed it to fit into the housing behind the amp. I put it all back together and instantly started working, and worked for my entire trip home, then again the next morning when I started it still working. I thought "what a great cheap fix to something so important as a Tachometer." (I won't buy a car if it doesn't have a tach)

Everything went well for about 2 weeks then a hard cold front set in and boom no tach again on cold start, but about 20 mins down the road and it would miraculously start up again. so I got to thinking what could have happened? the only thing I could think of was that the paper shrunk enough (we are talking microns here) because of the temperature change. so I am here to report that a 7/16" flat washer fits snugly into the housing and is thin enough you can still thread the amp onto the connection. and hopefully the steel flat washer will not contract too much with the cold and leave me without a tachometer again. ( so far so good)

I fooled around with cig butts, paper, etc for a few weeks, with nothing working for more than a few days. What I finally did was take apart the plug that the tach amp plugs into, and gently squeezed each metal 'socket' that the pins fit in. Don't crush it flat, just enough that it fits tightly on the pins of the amp. My tach has not failed one time since I did this repair... It makes me wonder how many good tach amps have been replaced because the pins are slightly worn, and dont make good contact in the plug.

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Mike
1983 Mercedes-Benz 300SD 270K
1960 Ford F250 62K
1990 Mazda Miata 156k

The thing is Bob, it's not that I'm lazy, it's that I just don't care.

Foam peanuts will also work.

W126 diesel uses the same trash can amp as the W123.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles