Rev counter problems

[silverlink]

Since restoring my Sprint (including new wiring loom) I've now got problems with my Rev counter bouncing.
I have standard points fitted in the distributor so should be no problem there and before restoring my car the Rev counter worked fine. I have a sneaky suspicion it may be a dodgy connection somewhere around the ignition switch, Its so long since I did the wiring I can't remember weather there's a bullet connection block in that area that might be causing a make and break in the wiring. any ideas what it might be.
Cheers
Ian

[billmoore42]

Ian:

My 67 FHC had a bouncy tach, which also showed increased RPM's when the car was left in the sun or otherwise in a warm area. This was fixed by a tachometer rebuild by Nisonger (I am in the USA) which has made it stable and reliable (they replaced the capacitor). I believe the capacitor gets old and dried out, and causes the bouncing and higher reading when the car is warm. My 2 cents.

[ericbushby]

Ian,
I agree with Bill. All electrolytic capacitors usually need replacing. They have a life expectancy of 20 years max.

When working as a service engineer on high power electronics, sometimes 50 years old, I would change the capacitors on the circuit boards before attempting to find the fault. Often the fault was cured by that alone.
They were due for changing anyway.
The customer thought I was Superman, because they had been testing for ages and got nowhere.

I changed mine when I went to negative earth for the alternator.
One thing that they do is absorb spikes and electrical noise from the ignition signal.
Best of luck
Eric in Burnley
S3SE DHC

[silverlink]

Thanks for the info guys,
Next question now is which is the best place to sent the tacho to for repair?
Ian