Circuit breakers inside the wiper and headlight switches are simply contacts on a strip of metal that bows with heat, much like the gauge voltage limiter. You may not feel or hear it.
take the drivers side or both wipers off. Will the shaft wiggle?
Wipers on our first 67 (mid 1980s) stopped intermittently until eventually stopped for good. Test lamp says fault is in the switch. When I took it apart that strip of metal was cracked in half. I drilled a small hole in the side of the switch, routed a piece wire out of it, figured out where to patch in one of those cycling circuit breakers that look like the top of a zippo lighter on the outside of the switch. At power up that circuit breaker cycled also.
Next I removed a nut to take the pitman arm off the motor. Power on and motor runs non stop. Root fault was worn/binding wiper pivots, especially the left where all the work load is. I'll add here that I was working as used car mechanic for Ford dealership at that time. I had noticed those other brands have wiper mechanisms outside the cabin. I wasn't happy with Chryslers noisy wiper mechanisms inside the cabin but... I had never owned a new one either. Low and behold, my 67 Chrysler wipers now run smooth and quiet.
Fast forward to when our 73 Valiant started tossing the plastic linkage bushings ( meant to make them quieter ) less than 2 years after replacing. OEM bushings had lasted 25 years so I pretty much knew where the problem was.
I didn't completely rebuild those pivots since that old beater had one wheel in the grave anyway. Knowing what I had found inside those first pivots, I simply marked them, then dropped them to apply reseal kits and grease and reinstalled rotated 180 degrees ( puts a less worn bushing wall to the worn spot in the shaft. Its a one sided wear pattern). Wipers ran quieter and I didn't have to replace those bushing again before she died a few years later.
The 67 B'cuda I have today... I bought it from the original owner and drove it home from Seattle WA. It had seen its share of rain, and sure enough, noisy wipers. So while I had that windshield and dash out of it, I rebuilt those wipers pivots also.
Thats all I know.
A test lamp will show you where power is and isn't when the wipers stop. You might discover that the wiper motor has a thermal protector inside it. Good luck
