Thermometer Gauge
 

My thermometer gauge is busted on a 82 300CD. Every time I turn on the lights the gauge goes from 0 to the 120 boiling spot. I'm guessing this is a short. I'm not electrically inclined and am hoping that someone can possibly point me in the right direction.

Check the engine to body ground strap.

May not be a short, may be an open. Pull the wire off of the temp sender (it's in the water jacket somewhere) and see what the gauge does. Try grounding the wire, see what happens. The sender is more likely to fail than the gauge, IMHO.

Jeremy