Tachometer stops working when lights on

[scharkie]

Hi, I have a 96 model. When I start the car the tachometer is abit slow to start. When I turn the driving lights on it stops. I have to turn the aircon on for the tachometer to start again. Has anyone come across this before?

[bee utey]

Tacho is driven by a wire off the back of the alternator. Check the small white/grey wire for looseness, also check that the drive belt isn't slipping. Your alternator may also be stuffed, check the output voltage with the lights on, engine running.

[DiscoMick]

Ditto the above. When my alternator started working erratically, the tacho would stop. Then they both stopped. Alternator was rebuilt, tacho resumed action, then became occasionally lazy. Got the alternator checked and it fine. Electrician changed the tacho connection and it improved, but still happens occasionally. Full set of new belts, so I assume that's not the problem. Hope that helps.