How to tell if my Truck is Positive Ground?

[Joxster71]

Hello all,

 

First time posting on the forums, although I have been reading these forums for a long time.      I have a 1941 Dodge WC which I bought about 6 years ago.     A few months after I bought it I bought a new battery(6v).    Back then I didn't know such a thing as Positive ground existed, so I hooked up the new battery negative ground.      So, this truck runs really good, battery charges, always starts....The only thing that doesnt work well are my headlights (very dim), which I think may be a grounding issue..  I know on the original schematic, this was a positive ground truck,  but I also know that it is possible to rewire to make it negative ground and someone could have done this at some point.

 

 

Anyway my questions are   1) would this truck run this good if it were hooked up wrong?    and is there anyway to tell if it should  be positive ground?

 

Thanks for reading,

 

Jacque

[Jerry Roberts]

# 1  yes .  When your truck was new it was positive ground .   

[TodFitch]

The spark may not be quite as hot and your points may wear faster with reversed voltage. But basically there is very little in a 1941 vehicle that does not have a radio that is voltage sensitive. Your ammeter will, however, read backwards unless you reverse the wires on it.

 

There can be an issue when switching polarities with getting the generator “flashed” (i.e. getting the residual magnetic field in the field iron cores setup).

[Ivan_B]

2 hours ago, Joxster71 said:

and is there anyway to tell if it should  be positive ground?

Do you still have the OEM cloth-insulated wiring? If so, It could still be +ground. If it was rewired, at some point, chances are it could've been switched to -ground. Otherwise, check the ammeter operation and the wiring against the OEM diagram, as Tod suggested.

 

For the dim headlights, you might want to clean and lubricate your switch inside. At least check whether or not the switch or the wiring gets hot during operation, you don't want that.

[Sam Buchanan]

When your truck was new it was positive ground. Since the ground cable is now connected to the - terminal of the battery it is now negative ground.

 

The wire on the coil that goes to the distributor should be connected to the (-) terminal of the coil, and the ammeter should be wired so you see a positive indication when the battery is charging. If those are not the case reverse the wires.

 

That's it. Carry on. 

 

P.S. My originally positive ground '48 Plymouth is very happy being negative ground after the above changes were made.

[Joxster71]

No, not original OEM wiring, it was rewired at some point.    Ammeter reads positively, which should tell me that my battery is hooked up correctly, which in this case is negative ground....        I will check the switches for headlights.....Dash lights super dim too...but when I put my brights on, they work really good.....

 

Thankyou for your help....

[Joxster71]

Thanks Sam, just saw your post......Ya i think It's good......It's been bugging me ever since I found out about postitive ground