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I bought a new wiper motor for the 56 I'm working on, I installed the whole system in the truck yesterday. There is no wiring harness installed yet but I'd like to test the operation of the wiper motor before starting the install of the Vintage air unit. The switch harness for the wiper has a single wire that gets it power from the ACC of the ignition switch. I'm assuming the ground would come naturally from the grounded cab.. today I tried running a ground wire to the body of the motor and that wire to the positive side of a battery and nothing happened. Am I going about this wrong? I just want to be certain things are going to work before I get too much installed under dash..
Would that not be negative ground ? Should have been big smoke to the positive term and ground, is the battery charged?
A single wire sounds weird because if it's a two speed motor then maybe two wires and also the park position inside the motor say hot even with the switch off so that it will park ?
It's a new Dennis Carpenter motor 12 volt negative ground .I assuming the ground is from it just being bolted on the firewall. 4 wires to the switch from the motor , a wire from the switch that has an inline fuse that gets connected to the accessory on the ignition switch according to the wiring diagram that came with it..I just want to make sure the thing works before I load everything under the dash.
That's the diagram I have, but I have no wiring harness in the truck at all as I'm only starting to assemble it. I would like to power the wiper motor somehow just to make sure everything is going to work properly. .I thought by putting a ground wire to the negative post on a battery and the power wire from the switch would activate the motor but I'm not having success. ..
Last edited by 56panelford; Nov 11, 2025 at 10:55 PM.
That's the diagram I have, but I have no wiring harness in the truck at all as I'm only starting to assemble it. I would like to power the wiper motor somehow just to make sure everything is going to work properly. .I thought by putting a ground wire to the negative post on a battery and the power wire from the switch would activate the motor but I'm not having success. ..
I would run a jumper from the ground on the battery to the housing and another jumper wire from the positive terminal to the different connections one at a time. You will not need the connector just two jumper wires.. That should work.
I just put this same unit in my 52. I bolted it up using rubber washers on both sides of the pivot arms to deliberately keep it isolated from the cab.
I just clamped a jumper cable to the motor housing and then the other side to the negative post of a 12v battery. The lone red wire coming from the switch goes to the 12v pos post. It parked and worked fine.
Took a minute to adjust the park position, but was very simple.
My truck is still 6v positive ground, so I'm using a 12v 10a converter to drive the wiper unit. The fuse in the kit is 20A, but I loaded the wipers down with my hands while they were running and only saw 7.5 A max on my meter.
It may not work forever, but it's worth a try, I figure. I could not repair the original wiper unit.
My plan is to pull one of the nuts off the wiper motor and run a dedicated ground to the ground output from the 12v converter. The positive from the switch goes to the positive from the converter.
The 6v input will come from the frame (6v+) and the negative from the key.
I loosely put everything together (still building out the dash) and it worked just fine.
I thought by grounding the motor frame and connecting the power wire that goes to the ignition switch to the positive post to a battery it should work. I know just because it's new doesn't mean something could be defective. How would I go about checking continuity through the switch..? I'm heading back out to the shop now, trying to finish up on the insulation in the cab..
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