squealing light shut off indicator noise comes on and off while driving

[chosenberg]

I have a 1985 300SD. My diesel makes this squealing noise if I turn off the car, and forget to turn off the lights. The noise tells me that the lights are still on and that I need to turn them off. Anyway when I'm driving the squealing noise while just come on and off intermittently. It will even come on sometimes when I turn on the turn signals Has anybody had this experience? Does anybody know how to fix it?