I was able to acquire a tachometer/clock for a W123 280E. How does the wiring of these things go? There are three terminals on the tach itself. One is marked with a + (+12V I assume), the center pin is grounded to the tach's body, and another one marked with a W-.

Any ideas? I tried hooking up the + terminal to a 12V source and the W- terminal to the negative side of the coil. Nothing.

However, when the center terminal is hooked up the negative side of the coil, and the W- terminal is not hooked-up, the tach works (although a few hundred rpms low).

My wiring doesn't seem right. Anyone?

Thanks and regards,

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Johan Limcangco
Manila, Philippines
79 350SE (W116)
86 230E (W124)
http://www.geocities.com/johan01.geo