How to test negative battery ground?

[signsup]

Rewiring fellow club members M37 and not much had run on this truck for a while. We test lights on the bench and make repairs and necessary, but when we install them on the truck, we get nothing. So we need to search down ground, IMO. Lots of rust and grease on this Dodge, so we want to start at the batteries and work our way to the fixtures. How do we test the negative battery cable to frame for good ground? Could be a bad cable with internal broken wires, or it could just be need to clean up connections well and reinstall.

What would be a good test for grounds? Thanks in advance.

[RCrombie]

I would get yourself a multimeter and check to see if you have voltage out to the lights or not. That would be a good starting point. You can run some jumper cables from the negative post of the battery to a clean spot on the frame and see if that makes a difference. If it does, you know you have a ground problem and will need to check and clean any connections.
Good luck!

[signsup]

We have the multi meter and get 24v to the licht sockets, all headlights and marker ligh lights. We test the negative battery terminal to the frame connection of the negative battery cable and get 27 ohms of resistance. Could be 280, 2800, 28000 as our meter is a little funky to read the gauges.
Light socket to frame is 9 resistance.

If I disconnect the battery cable from the battery and the frame and test it as a stand alone, should I get 0 resistance?

Again, just trying to determine what and how to check to make sure I am getting good ground at the bulbs.

[RCrombie]

Well, it sounds like you’re on the right track then. Yes you should get 0 resistance when you check the cable on it’s own. However, if the cable looks to be in questionable shape then you are better off replacing it anyway. Minor amounts of resistance will still cause issues with starting a vehicle, due to the amount of current required. The name of the game is to have as low a resistance as possible when it comes to grounds.
Cheers,
Rob

[Cal_Gary]

I agree with rcrombie-get a new cable. I'd also grind down the ground mounting area then attach the new cable with some dielectric grease sandwiched between the cable end and the mount point.
Gary

[NAM VET]

my truck had/has one of those woven wire "cables", about an inch wide, it was in good shape, but like mentioned above, I used a wire brush to get to fresh metal on the frame. Long years ago, I had an MGB, which had two 6v batteries under the rear package shelf where they were exposed to all sorts of road grime. I had to clean the terminals often to get any juice. Good luck, NV

[signsup]

Two shade tree mechanics working on the same truck spell problems. I went under the truck to remove the negative cable from the frame and asked my son to pull it out from the battery compartment. He was pulling one cable and I was pushing the other. After he disconnected the battery cables to start the rewiring process, he put the cables back on and presumed the red colored terminal ends were positive. Nope. We had the cables connected wrong at the batterys. Moved them around and headlights came right on.
Rest of process will go together easy peasy, we hope.

Thanks for the guideance.

[RCrombie]

Haha well that explains it! At least these vehicles are pretty robust when it comes to being hooked up backwards. I’m glad you guys got it sorted out. On to the next thing!

Cheers
Rob