Hey guys,

I have a small issue with the tacho in my Sierra RS Cossie. The tacho is working but not reading correctly. At crusing speeds it reads about 1000rpm and when I run through the gears to what I think is about 5000rpm, it only reads about 2500rpm.

Before I go taking it apart, any idea on what might be causing this?

 

First off have you changed anything (Adding wasted spark etc?) If no I should think it's a bad connection or track on the PCB.

Martin

 

As said if not changed over to WS, that's just how they go I'm afraid, they can be repaired and even reworked inside, tap the tacho and see if it jumps when stuck, occasionally the centre of the dial face lifts and physically stops the needle from moving freely.
tabetha

 

I've only had the car a couple of weeks but as far as I can tell it's a stock car except for a stage 1 chip and mongoose exhaust. The needle still seems to move freely enough, it's just that it doesn't read correctly. Thinking it's bad connection or an electrical issue of some sort causing the faulty reading.

 

They're very simple instruments, but do go wrong, esp with age, you could always try running a different earth direct from the battery to the rear of the rev counter, if that fails add a new live direct from coil negative, this would remove old wiring's high resistance, post up results if you do, would be interesting for others.
tabetha

 

Thanks, I'll keep you posted