UK Car Repair: Fiesta xr2 rev counter, fiesta xr2, mk2 fiesta

Question
-------------------------
Followup To
Question -
Hey,
I have just bought a F reg fiesta XR2 and for the first 10 miles or so the rev counter worked fine but since then hasn't worked at all. I would repair it myself but can find no documentation or information on even how a tachometer works!
Please could you give me some help as to how the tachometer works and where I should examine?
It is a Mk2 Fiesta with the 1.6 CVH engine.
Many thsnks
Answer -
What year is your fiesta? And is the tachometer digital or analog?

The tacho is an analogue tacho, as fitted as standard.

John


Answer
Ok, I am still unclear as to which one of fords worthless ignition systems this car inherited. So, well go for broke and describe both. The single coil system is by far the easiest to check. The positive terminal is the signal for the tachometer and more times than not is part of the dreaded EEC IV or V system. The loss of a tach signal can be a poor connection at the coil or a bad gauge. The other system would be the EDIS system where a 4 pole coil pack is triggered by a crank sensor. The EDIS unit offers a signal to the gauge and can sometime become faulty. However, I would try removing the gauge cluster, cleaning the plug, and reinstalling. If that doesn't work, try rapping on it. If it works intermittently when whacked, you have a poor internal connection you will have to replace it. I would chock it up to a bad gauge that was rigged to work "the previous owner hit it until it worked and then shut it off until you arrived to look at the car".

Try that and get back to me.

John