Rev Counter Problem.

[Tdm]

Went out in the Stag last night and all was fine till I switched the lights on.
As soon as I did so the rev counter dropped to zero, but on tapping the glass it burst into life again but would only read between 1,000 and 2,000 reves when I was doing 70mph so it should have been reading about 3,500 revs.
When I got home I left the engine ticking over but switched off the lights and the rev counter operated as normal again. Switching the lights on again saw it plummet once more to zero.
Any suggestions as to the cause - obviosly it is going to be an electricasl fault, is the rev counter and the lights on the same fuse circuit ?

[ams]

imported post

Hi,

could be the earth to the rev counter has gone high resitance and is earthing through the sensing circuitry, or at least in part. So when you turn on the lights the guage pannel light bulb finds it's earth through the sensing circuit and upsets the pulses to the rev counter. Ensure the rev counter casing is properly earthed and the bulb holder is secure in its' mounting tube. This will be accesable from behind the dash.

Hope this helps.

Andy.

[jamcarr2]

imported post

Hi Terry

I had a very similar problem last month but mine was when I put the indicators on I tried every thing , earths ect .In the end I bought a new one and its been fine ever since

JOHN