Chrysler Repair: 98 T&C rear wiper, wiper motor, control switch

Question
The rear wiper motor on my 98 T&C starts running whenever it decides to.  It will run for 30 seconds to a couple hours then it stops by itself.  While it is running from self starting the controls do not work in that you can not stop it or change mode from full time to intermittent.  All the controls work fine if the wiper has not self started and it will not self start if you have already engaged one of the functions.  If you shut the car off while it is running from self starting, it does not continue running when you start the car again.  Took it to the dealer, but they could not make it self start.  The self starting is getting more frequent, the duration of run time before it shuts off is still random.

Answer
Hi Floyd,
The rear wiper control switch on the HVAC sends a coded signal to the body controller and the body controller then activates the motor in response to the message. The motor also has a self-parking function and if that were defective it could keep running even though the body controller didn't ask it to. Pin 2 at the motor plug is the one from the body controller and it should always be at 0V unless you had turned on the wiper. If you find when it is running on its own that instead it reads 12V then that would say that either the switch at the HVAC is faulty of the body control is misreading the signal or is failing. If it was reading 0V when it was running on its own, then that would say the self-parking feature is causing it to start and run until it decides to turn itself off.
In that case you could open the motor and examine the self-parking contacts which may be too close to one another and self-starting for that reason.
Roland