Tach troubles

[Stephen]

I thought I had this solved with a bad ground but it still pops up once in a while
My tachometer drops out, then seem ok not sure if colder temperatures effect it, seem to happen more in the cold weather. Is there something I'm missing? Wiring is right grounds are good. No sure if resistor is opening or going bad has anyone ever had this problem

Stephen

 

[Tom H]

Stephen, I have worked on over 2 dozen Alpine tachs. I have not seen any internal malfunction that would cause one to operate intermittently, but , of course, there is always the possibility of a component going intermittent. After all there are many components inside and all are 40+ yrs old.

But the biggest cause of intermittent operation I have seen is that the steel c-clip that the white wire loops thru on the rear does not make solid contact with the tips of the mating half sticking out from inside the tach. That steel C-clip is one half the core of a pulse transformer that couples the signal of the coil pulse into the circuit inside. If the tips of that C-Clip do not make solid contact with the mating tips (of the other half of that transformer core) you do not have a good transformer and the pulses will not get coupled into the circuit.

One other suggestion is to check the ground of the tach, by turning on the lights including the Dash lights. If the Tach's light does not come on, you probably have a poor ground. If it does light up, you know you have a good
ground.

Tom

 

[Stephen]

Thanks Tom the loose clip might be the problem seems a little loose I will check that the ground is good