Tach goes to zero when headlight switch is on?

[ftsoft]

I've only had the headlights working for a couple of years. I have noticed that when I turn on the headlights the tach goes to sleep. After looking at the wiring diagram I can't seem to figure out why this would be. Anyone suggestions appreciated.

Frank

[Mazzini]

It's the earth on the back of the tach.

[ftsoft]

Yep.. That was it. Nut was loose. Thanks.