OK, I replaced just the tach "guts" from a pull-a-part W126, or maybe a 190E (I pulled 2 and don't know for sure which is which now). They were both 7000 rpm and were stamped with 004, which is the same as mine from my 560SL. The circuit board was shaped a little differently, but all the components looked the same. I removed just the tach mechanism and installed it on my 560SL plate with my original clock. Fired up the car and the needle shows the car idling right, but when I punch the gas, the needle only goes to about 1300 rpm, or so.

So, it works at idle but won't work on acceleration - any ideas? I was very careful with the needle this time and didn't push it on too hard - either you can't interchange these because some signal, or the tach itself is different; OR whenever you pull the needle off, it is hard to get it back without maybe bending something inside the mechanism??? Anyone had this problem before?

I don't know, although the needle moved smoothly and returned to 0 before I put everything back together.

ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE