Pos ground or neg ground?

Got my 35 ford wired with a harness from Mac's. Something aint right. Starts, runs, beep's, and shine's, but I cant hook up my cut out with out a bunch of sparks. I didn't have wiring in the truck before. My question would be how to tell if the generator/cut-out is wired up neg or pos ground. I have found threds and articles on late late model flatheads but none for early 21's. Any info will be helpfull.

 

If it is the original six volt system it would be positive ground.

One way to tell on a vehicle that still has the original wiring on the coil and distributor is that the side of the coil that connects to the distributor will always be the same as the ground on the battery.

 

I wired it up with macs diagram as well as vanpelts diagram (stock 6v pos ground, but what is the process for changing from pos to neg groung and how would you tell if the wiring for the gen/cut out has been changed?

 

Is the cut out a solid state cut out? Cut outs were famous for sticking with the contacts still connected. I came back several times to find my freshly charged battery run down because the cut out contacts had stuck.

If your contacts are sticking it would spark when you connect the wires because the circuit is complete. Back when I had mine there was a local guy that used diodes out of an alternator to solve this problem. Later on they became available from places like Macs or most any early Ford parts store. If you don't have one, get one.

You check the polarity of your car by looking at the ground cable on your battery. If it goes to the positive post then it is a positive ground and hooked up as Henry intended. If the ground cable runs from the engine to the battery neg. terminal then it was changed sometime in the past.

I'd suspect the cutout as your problem.

 

If you are running the old generator it will need to be polarised. This is done by running a wire from either the "hot" side of the battery or the "BAT" terminal of the regulater to the field terminal of the generator- do not attach this wire- just a momentary contact is all you need. If the engine is running when you do this you will hear it pull down a little as it starts to charge.
Any generator can be polarised to charge neg or pos ground so just remember to use the "hot" side. A generator will need to be polarised if it has been sitting unused long enough to lose it's magnetic properties. A generator that has opposite polarity from the battery it is trying to charge will work against the battery untill one of them dies. The cut out, coil, radio, and ammeter are about the only components on a simple old car that are polarity sensitive.