Electric Wipers

A note on wipers.  After going through a recent snowstorm here I’ve decided to finally give up on my vacuum wipers.  They were OK for light rain but they just couldn’t hack anything more than that.  A snow storm or heavy rain would shut them down.  I was lucky and found a couple of top-mount original Jeep® electric wiper motors on ebay recently.  I’ve installed these and they seem to be much better than the vacuum wipers were.

The motors I put in were top-mounted to replace the 2 old top-mounted vacuum units.  I found that there were some issues when doing this as a retrofit to a Jeep® that never had them installed before.  One of these is how to get both motors to “park,” or return to a default position every time you turn them off.  There is a park circuit built into most electric wiper motors and the ones I installed have this as well.  What happens when you turn the motors ON is you send power to the “run” terminals of the motors and they run as expected.  When you turn them OFF, what you are actually doing is sending power to the “park” terminals of the motors instead of the “run” terminals.  The motors will continue to run until they reach a predetermined parking spot and they will then shut themselves off.

However, when you are dealing with 2 separate motors, not 1 single motor like most vehicles use now, there can be a problem when parking them.   Originally they handled this problem with a rotary wiper switch on the dash that had separate power running to each motor.  In my case, I’m using a SPDT toggle switch for wiper on/off and I’m “sharing” the “run” power wiring.   Unless you add some diodes (or in my case a full wave bridge), when you try to park the motors, if one of them parks but the other is still running (very common), the one that’s running will power up the parked motor through the shared run circuit wiring.   Makes it real hard to stop them unless and until they both reach their park positions at the same time.

Below is a link to a wiring diagram that might be of interest to others with this problem

Wiper System Schematic

I also had a problem with one of the motors running too fast and it turned out I had a bad ground from one of the coils inside the motor case.  Below is a link to another diagram showing that problem.  I added a jumper from that coil wire to ground and that solved this problem.

Wiper Motor Schematic