Stick in the middle of the screen or stop in the middle of the screen when switched off?

If they stick, you'll need to check the linkage (which is inside the scuttle), if they stop where ever they are when you switch them off, there are a number of possible causes, there is a park cam & switch arrangement in the motor that could be defective, or it could be a wiring issue, I've seen this caused by corrosion on the motor connector, it's right behind the battery.

 

Thanks for your response. They stop (come to rest) in the wrong place. There is a crack in the windscreen glass exactly where they stop - I think it may be connected to that damage? See below pic.

 

They stop (come to rest) in the wrong place.

The wipers come to a stop when the motor driven pawl pushes the park/run switch to the park position AND the wiper switch is in the off position. Keep in mind the pawl pushes the park/run switch to the park position every time the wipers return to the park position but if the wiper switch is in either HI or LO the park/run switch is ignored. It sounds like your pawl cam is no longer in sync with the wiper linkage so the wipers are stopping in the wrong place. I'm not experienced enough to know if the pawl cam can be realigned or if the wiper motor needs to be replaced.

Google says this:
To realign a wiper motor's pawl assembly, you must first disconnect the battery and remove the wiper arms and cowl to access the motor and linkage. With the motor running, detach the linkage. Then, place the motor's shaft at its park position, often vertical, and reattach the linkage so the wipers rest at the bottom of the windshield when off. Cycle the wipers to check the full travel and adjust the linkage points as needed.

 

 

Or just get used to the timing of the wipers, so that you ‘learn’ to shut them off when they hit downward most position.

 

‘learn’ to shut them off when they hit downward most position.

I'm not a wiper expert but I don't see how that would work. The wiper switch is in parallel with the park/run switch. So even if the wiper switch is opened, the motor will not stop turning until the park/run switch is opened. And that is happening at the wrong position. If a person were desperate enough, they could cut the YEL/BLU wire at pin 2. The motor operation would then be completely under the control of the wiper switch and they could stop the wipers at any position.

 

I’m not a wiper expert either, and perhaps the newer wipers work off of a different system, but not wanting to go through the repair steps for this, this is how I’ve been turning my wipers off for years.

 

this is how I’ve been turning my wipers off for years.

I believe you. But I don't believe your car left the factory with that feature.

 

Just to clarify...

1. At one time your wipers automatically parked themselves at the bottom of the windshield.

2. One day they began stopping at random positions on the windshield.

3. You learned to time the wiper switch to park the wipers at the bottom of the windshield.

 

1. Yes, at onetimemy wipers shopped at the bottom of the windshield.
2. One day when I turned them off, they stopped exactly where they were and did not return to the bottom of the windshield.
3. I have learned to turn off the wipers when they are just about to reach bottom So that they stop at the bottom of the windshield.

 

Based on the evidence it appears your park/run switch died in the "open" position. That was really lucky for you. But the original poster's park/run switch did not fail. It just got out of sync with the motor. He can't stop his wipers at will like you can. He would have to disconnect the 12-volt feed at pin 2 (in the schematic above) to be where you are.