strange one! just recently the rev counter on my saff is behaving rather odd! when you fire the car up from cold the rev counter reads about 2000rpm more than it should ,it will read 2900rpm when the car is ticking over etc, and as you start to drive it will rise just giving a higher reading than it should. after around 10 mins of driving it jumps back down and reads normal again and will do all day unless you leave the car for a few hours ,then its the same again. anyone any ideas please ?

 

The fault is simple, it's a FORD.
The tacho's are not the last word in engineering terms, and can suffer all manner of problems, very often running another earth direct from the battery to the plenum cover cures a lot of odd lecky problems, doesn't need to be a thick wire either something like 14/030 is fine.
tabetha

 

I've got a Mint Sapp Rev Gauge for sale if you need one see my for sale thread:
https://passionford.com/forum/ford-r...oads-more.html
Cheers Rich