Rev counter repair

[Bigjcc55]

I recently bought a rev counter as spares or repairs, I tried plugging it in today to see what worked and what didn't, everything on the pcb works apart from the rev counter.
I've checked for a signal from the green wire on the multi plug and get a pulse on the test light, so from what I can gather I have power but no working rev counter.
Is there anything else to check?

Thanks

Jc

It's on the camper so it's petrol and late wiring.

[Bigjcc55]

Any takers?

[dave friday]

Is it a Diesel rev counter [a petrol one wont work!]

[Bigjcc55]

I'm sure it's a petrol one there is no glow plug light on the pcb, and from the pictures I researched the green shaded area on the rev counter looks correct for a petrol.
I'll plug it into the van just to be sure it's not for a diesel.