Sounds like a circuit breaker is killing power to the motor then reactivating power when it cools.

This sounds a lot like water getting into electrical somewhere.

You could test this by keeping it out of the weather, letting it run (unoccupied) with the heater on full blast for an hour to dry things out, then keeping it out of the rain while actively testing and/or passively testing for the issue to return. You might even need to tarp it so water has no chance of leaking in through a leaky door or window seal.

Do you still think re-flash?

It looks like more diagnosis is needed. You could try flashing it, but it costs more money than chasing my water intrusion theory.

I’m game! It has been in the driveway for weeks. My daughter took my wife’* car back to college…

Your first comment suggested, “keeping it out of the rain while actively testing and/or passively testing for the issue to return.”
Just to clarify:

• The issue (wipers always on with accessory or engine power) never went away, and is still quite persistent and predictable.
• We did have the surprise of finding the wipers on Sunday morning with no key in the ignition.
• There has never been any interior leak, damp carpet, or musty smell in the car.

Also, I don’t have the best hearing, but I kept thinking that I was occasionally hearing a faint sound seemingly coming from the firewall area, near the antifreeze reservoir. It is not like the “click” of a relay, but more muffled like something switching on and off?

My wife verified hearing the sound.

It doesn’t seem to be coming from inside of the car because I can barely hear it when I’m inside the car…

It’* not coming from the wiper motor or any relays in the fuse block…

Sometimes it one click, and then click click…

This could be normal, but I don’t know. Is there a fluid level switch on that reservoir?
I’ll try running it with the heater on even though there are no signs of interior moisture…

Maybe the motor was cycling on and off Sunday morning because the wiper motor running drained the battery down, but that doesn’t explain why the motor was on with no key in the ignition.

if I don’t find out soon, I’ll have to bite the bullet and send it to the dealership or an auto electric shop. My daughter took my wife’* car back to school…

There is something closing a circuit for th wipers to run. The most likely suspects are damage and water. I'm looking forward to finding out if "cooking" the car helps with the issue!

If this is intermittent a flash will not help.

The issue is not intermittent.

Ever time that the key is turned on (accessory, on, or engine started), the windshield wipers come on, in low mode, even though the switch in the OFF position.

The wipers did come on one time (Sunday) with no key in the ignition (with the switch in the OFF position. That hasn’t happened again.

If you can verify the switch is actually turning off then I would flash it or replace it.

i would too, if he had a scan tool, it would tell us if the BCM is getting a request for wiper or not. BUt the switches of this era are known for being spotty so

No new BCMs available for this car.
Runs great, everything works, but giving up on getting a BCM programmed for my VIN and security settings.
Buick can’t program a used BCM.
I don’t have a TechII… (ACDELCO TDS wasn’t sure if a TechII would do it)
Tried to get computer repair guy to solder the existing BCM chip on a compatible BCM board. Didn’t work (I don’t think he was very good)…
Cutting my losses…

What is a good price to ask to sell for salvage?