The Stovebolt Site Forums The Shop Area The Electrical Bay 6 volt windshield wiper motor for GMC

I purchased an electric conversion from Brothers for my '53 GMC six volt positive ground. The installation schematic specifies the motor be terminated at the positive terminal. I contacted Brothers about running the motor connected to the negative terminal and their response was they didn't know and I should contact an electrician. That wasn't much help so I briefly ran the motor both ways, with a positive and then negative connection. Somewhat surprising, the motor rotated the same direction. I thought it would possibly reverse rotation. Not totally comfortable with this result, I contacted another vintage truck parts supplier, that offered the same conversion motor (at least the picture looked the same). They were much more responsive. The tech didn't know the answer but he did contact their supplier. Their techs weren't sure either but didn't think the polarity of the power supply would matter. I still have some apprehension about running with negative power supply if there are some internal control components that require positive power.

So, my question is, has anyone installed this conversion with negative power to the motor and not experience problems?

I’m a little unsure of which question(s) you want answers too. The motor you have is a permanent magnet type. It will turn the same direction however the polarity is hooked up. The technicians you spoke with need to find another type of work.
Are you changing the polarity of your truck? If so, ask how to do it on this forum and someone like Jerry and others will show you the ‘path’.
I know of no “internal control components” that would be effected by the reversal. Your radio has a ‘chopper’ in its front end and I am unsure about and the polarity of your filter capacitors. That question can be asked in the other section of the electrical forum. Reversing the wires on your amp meter is a ‘no brainer’. Hope this helps.

Permanent magnet motors reverse directions when the polarity is swapped- - - -that's how power windows and power seat motors change directions. Field coil electric motors (like starters and some heater blower motors) turn the same direction regardless of polarity. Check the motor to see if it's got field windings or thin magnets in the housing around the armature.
Jerry

Oops! Missed that one Jerry. Maybe I’m the one who needs to find a new line of work. Wait a minute...I’m retired!

Thanks for the feedback guys. I did briefly run the motor by reversing the polarity and there was no change to rotation, so it may have windings and magnets as you suggested Jerry. I guess I will run with the negative polarity and see how long it lasts.

I decided to contact Brothers to see if another tech may be able to contact the vendor of their conversion kit, which they did. Their tech Tim responded back within half an hour. The vendor suggested bench testing the motor and if it did not reverse rotation it should be OK to run with the negative polarity supplying power. Problems solved, my wiper motor and my faith in Brothers.
Bill