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Howdy - I have an old 7" prestolite DC motor that has a tachometer shaft on the end of it, and this motor came off of a parts car I was using that was complete with the tach cable + dash display. I just hooked those up, and didn't realize that my electric reverse was going to cause an issue. Heard an audible click coming from the tach on the dash when backing up into my driveway on the trial run.

I don't know - it might be harmless but I don't think I can ignore the clicking - just has that sound like it's stripping something out. And fair enough - probably wasn't really designed to have the motor turn backwards like I'm doing. Have unhooked it for now.

Just thought I'd check - does anyone know if maybe more modern tach displays can go both ways without issue? This one is from the 80s, pretty old.

Or if maybe there's some sort of a 1 way adapter that would drive the tach in forward but let it freewheel in reverse? Maybe something from the forklift world? (not that I've ever seen a tach on a forklift)

Just tossing this out there in case someone's run into this one before. I'll probably ditch it and eventually get an optical tach working, but this would be nice to have if it's something simple I'm missing. thanks
 

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Just thought I'd check - does anyone know if maybe more modern tach displays can go both ways without issue? This one is from the 80s, pretty old.
Since modern tachs are electronic, rather than cable-operated, I don't think newer is likely to be the solution. An electronic tach using a pickup on the motor shaft would be the logical solution.
 

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A mechanical tach should be just a rotor and coil setup. The rotor has magnets and induces a voltage and the indicating meter reads that voltage. The clicking you hear is probably the indicator needle getting banged into the low position stop. You could put a full bridge rectifier into the guts so it always has a positive voltage if you can get it apart. ICE motors don't generally run backwards well. OR if it has a zero set adjuster, you could move the needle to 1500-2000 rpm when off and let it be off by that much, assuming you dont rev it that high in reverse.
 
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