I have a 4 cylinder 1987 Volvo 740. The wipers just started coming on when I turn on the headlights. I've unplugged the wiper motor and sprayed WD40 and plugged it back up to get out the moisture. No luck.

 

No clue. The wiper control is not the same switch as the head light switch. Maybe you have a bad relay somewhere. So, when you turn the lights back off the wipers go back off? If that is the case, my guess would be that you have some bad wires somewhere and the coating has come off of the wires and you are making contact on bare wires.

Those cars should have been recalled because of the wiring that Volvo used to wire the cars with. The wanted to be "eco friendly" or "green" and used wires that were made of a recycled rubber coating. Well, the coating started deteriorating to the point of coming off the wires. You touch them the the rubber just falls off. Lots of Volvos burned to the ground because if it.

 

You should have posted this in the 240, 740, 940 section.

 

Bad alternator,get a multi meter out and start the car and check the voltage it should 14.0-14.5 on the good side and 13.8 low side.Most parts store will check it for you for free if you can get the car there with out dieing.