I had to fix this in my merc and town car,The first I had a mechanic do and it cost about $80.00.If you open the wiper motor cover there is a type of pendulum looking piece of metal that wears out and won't park the wipers any more.I found afterwards that it was cheaper at a local junk yard to buy the entire assembly and switch it out.This is what I did for the town car cost was $10.00. I think 92-98 would work so get as new as you can and it should work for a while.
Windshield wiper motors have an internal switch that allows a wiper motor to stay running long enough to keep the wipers moving until they reach the "park" position. Once the wiper gets to the park position, the wiper motor is shut off. The internal switch often fails and either the motor will shut off immediately, wherever it is or it will keep running. It sure seems that you need a new wiper motor.
Into Park or out of Park?
Usually it is part of the wiper motor.
the park tab is bent. it is a thick piece of metal that must be bent back slightly toward the wiper motor with a hammer or plyers. I assume this issue started when there was snow/ice on the windshield?
It is in the motor.
The wiper motor doesn't turn off until the wiper arm gets to the "park" location. If the wiper motor never detects park, the wipers will stay running.
The "park" switch inside the wiper motor assembly has failed.
Probably because the park switch in the motor is bust. This supplies the motor with electricity (after you switch off the wiper) until the wipers are parked (i.e. returned to off position).
The wiper motor assembly includes a "Park" sensor.The sensor shuts off the wiper motor when two conditions are met:The wiper switch is in the off positionThe wiper blades are in the park locationIf the park sensor is either damaged or dirty, the wipers will keep running.If you are at all mechanically inclined, try opening the wiper motor assembly and see if you can clean the slide contacts that make up the sensor.If that isn't helpful, replace the assembly.
You need to start by disconnecting the wiper arm assembly from the splines on the wiper motor itself. Then you need to jog the motor, once, through its cycle until it stops at its "park" position. Turn off the key switch. Then reconnect the wiper arm assembly to the motor when the wiper blades are in the proper position on the windshield. Turn key back on, and test run the wiper motor to make sure the blades aren't going off the edges and that there is no binding. Adjust as needed. Reinstall all previously removed covers and cowling.
It's possible that the wiper switch is bad, but most likely it's the wiper motor itself. Wiper motors have an internal switch that only turns off when both the manual switch is turned off AND the wiper blade is in the park position. If the wiper motor cannot sense that it has hit the park position, it will run continuously.
: There is a pawl located in the wiper motor that tells the motor when to shut off and leave the wipers in the parked position. : if your wiper blades park in the vertical position, this pawl has broken off. : the motor more than likely needs replacing.