1990 Ford Ranger Turn signal

God lord... That's a new one. For this to happen, there has to be a short to power between the signals and the wipers. My first guess would be in the steering column. Have you taken things apart to see of there is anything that looks damaged or a wire that has worn through and is shorting?

Does this happen if the lights are off and you turn the right signal on?

After I replied, I thought of another possibility. Have you checked grounds? If there is a weak or bad ground, power will take the easiest route to find a ground. It could be through the wiper motor causing it to turn on.

Just a thought... let me know.

Yes lights can be off. Its only when the high beam is in the on position. I will check everything you suggested. Thank you very much

Let me know what you find.

I checked everything and all grounds are good no bare wires. I'm thinking its just a bad switch or its the wiper motor. I will check the wiper motor. Thank you will let you know what I find.