86 Jetta engine temp problem

hi, i have an 86 Deisle Jetta and recently i noticed that when i turn on my headlights the engine temperature gauge goes up to about 3/4 rather than the normal range of about 1/2. Any idea why? thanks

check the engine earth strap,and other/all earth points.should cure your prob.

Nope, had a vanagon, and it seemed to do the same thing, I checked all the grounda, then finally changed the alt. to a gm style, and it worked...

oh, by the way it's "diesel" lol