Ok, here I go. I hope this straightens things out for you. Please don't be offended if I write something really stupid that you already know.
The wiper operates off of 12v negative ground.
First, right click on the image, save it and print it. It's easier if you have it in front of you for reference. H/T to
@ohanacreek for this drawing.
View attachment 19887
Second - Here is the relay I used...
Dorman Conduct-Tite 88069 - Relay | O'Reilly Auto Parts
All this relay is used for is to route ground to the wiper. The pins will be marked properly on it.
I also use this for all my grounds:
https://www.amazon.com/dp/B00X326A1K/?tag=sxsweb24-20
Here's how to wire it and the wiper:
The red wire from the motor is connected directly to +12v. Not accessory power. The wiper motor must have a constant +12v for it to be able to "park" when turned off.
The yellow wire from the motor is connected to ground.
The green wire from the motor is connected to pin 87a on the relay.
The black wire from the motor is connected to pin 30 on the relay.
Install a jumper from pin 86 to 87 on the relay. Include a wire long enough to allow pin 87 to connect to ground.
Pin 85 on the relay is connected to the switch you plan on using.
Here's how it all works...
When you turn on your wiper switch it turns on the relay. This causes the contact to close, supplying ground from pin 30 to pin 87 which supplies ground to the motor. Since the motor has a constant +12v coming in on the red wire the motor turns on.
When you turn off your wiper switch the relay is turned off, removing ground from pin 87. Pin 30 is now connected to pin 87a of the relay. This engages the park switch (internal to the wiper) which allows the wiper to return home (park) instead of stopping in the middle of your windshield.
If you are using the Cooper Bussmann PDM I would just use one of the fused outputs to supply power to your switch. The relay it is powering is drawing minimal amperage.
How'd I do? Hopefully this makes sense.
