Tachometer Not Working

[Savage Larry]

My 1978 tach isn't working in my car. It sits at about 1200rpm when the car isn't running but when I start it up the tach just goes to zero and sits there. I checked all my grounds as well as the wire going to the distributor. Am I missing anything or do I have a bad tach?

[Jack]

Most likely you do as it seems to be receiving power and signal. Try moving it with your finger very gently, maybe its just stuck.

[Savage Larry]

It's not stuck because it moves to zero when the engine is started. I'll order a new one today, hopefully that is the issue. Are the OER ones good? I'm hesitant to order repro parts because of the terrible quality of a lot of them.

[Jack]

I should have clarified "stuck" to a position, at least mine was like that, it would not go past 3k rpm, I was able to get it working by moving it past the stuck position.

[Wallington]

The tacho isn't meant to return to 0 until ignition is turned on and it is powered up, otherwise it just hangs down to the ground. But obviously the rest of the operations aren't right either. An instrument guy might be able to have a look, often they need to replace or adjust the circuit board inside, not a fun job. I destroyed 2 by accident trying to combine the best of each.