Can anyone explain how the wiper motor works on a 69? I have a brand new motor that works sometimes if I put an extra power source to it... I thought it was just power no power and ground but it seems like it needs a return location power source.
You should have power at the motor ignition on. Yellow wire center connector on the plug at the motor. The wiper switch supplies the ground for each speed. The other 2 wires. There are some diagrams here https://www.buick-riviera.com/servicemanual/120-93-153.pdf
To make the motor park, the case has to be grounded, negative is applied to the right terminal, and hot is applied to the center terminal. This is shown at about the 5 minute mark: .