Tacho dies when on highbeam

[chrisr65ls]

I just noticed that when I flick to high beam the tachometer needle drops to zero and stays there until flicked back to low beam. Any suggestions?

[Barry]

The high beam light switch itself has nothing remotely to do with the tacho, however the tacho impulse wire and the high beam indicating light share the same multipole connector on the back of the tacho. High beam is on pin 1 and tacho impulse on pin 5. There is also the +12V feed that the tacho depends on for operation on pin 6. If any of these wires were shorted together that might well cause the tacho not to work.

[mrclubike]

Does the High beam indicator work normally if not  check for battery negative on  the brown wire at the connector on the back of the  tachometer.
The Tach may be getting its Neg back thru the high beam circuit and when you turn the high beam on it goes battery Positive. causing the tack to stop.

[Bob_Roller]

There is a PC board inside the tachometer .
Been a while, but I think you can remove a few small screws and get a look at the board without taking the tachometer apart .
You can't get the board out, but you can position it to where you can get a  look at it and see if anything is obviously wrong .
If you don't find anything out of the ordinary with inspecting the connector and wiring, you may want to check this out .