1992 Dodge Caravan This Year Our Developed Odd Habits That Understand Would

This year our 1992 Dodge Caravan developed some odd habits that we don't understand and would like an answer. After the van is sitting and turned off for hours the headlights come on by themselves and after we start the engine the wipers come on by themselves. You can't turn the wipers off without disconnecting the connection clip under the hood, and we have to unplug the headlights so the lights don't come on by themselves. We replaced the turnsignal dimmer switch on the column and things seems to work for 5 or so days, but the old symptoms return again. We replaced the switch twice with same result. We took the Van to our local mechanic and he can't figure out either. Please help us!