M37 battery cables

[slk]

I have noticed that I seam to have an extra ground cable on my batterys. The first battery closest to the front side of the seat has the normal original red cable going to the + side. Also on that battery on the negative side is a ground cable going somewhere. ( Way to cold right now to get under the truck so see exactly where) then off of that negative side you have the usual jumper to the second battery to the + side of it , and then there is the original ground cable connected to the negative side completing the circuit. Has anyone ever seen an extra ground cable on the trucks like that.

[Elwood]

Did a previous owner set up something to run on 12v?

[slk]

That is exactly what I was thinking, but I do not see any other wires to the positive side. I was thinking I could just leave that cable off. I see no reason why it would hinder anything. This truck was part of the fire dept at one time so no telling if a siren could have been added at one time, or radio. I do not see any extra wires going to anything under the dash.

Steve

[Elwood]

If everything on the truck is 24v, there's no reason for that intermediate ground cable.

[slk]

I honestly do not see anything extra on this truck that would make me think there was anything needing 12 volts. It is still all 24 volt....

I did post something a long time ago about a small push button on the dash. When pushed it kind of makes a buzzing sound. Have never figured that out yet, but everyone here said that button was not original to the truck.

Steve

[Elwood]

That button and buzzer is the self destruct circuit. Don't hold it down too long.

[John Mc]

If your batteries are wired as two 12V in series, there is no way that both of them are grounded. If both negatives were grounded, the connection from battery 1 positive to battery 2 negative would also be grounding battery 1’s positive post.

[slk]

If your batteries are wired as two 12V in series, there is no way that both of them are grounded. If both negatives were grounded, the connection from battery 1 positive to battery 2 negative would also be grounding battery 1’s positive post.

Now that is a thought. That would act as a direct short. The cable size is a little smaller but not by much. I need new batterys in the spring and will be replacing them both at the same time. Just trying to get my ducks in a row before going forward.


The images below are what I have right now. There is a disconnect lever in the mix as well. It acts like a good deterrent for theft if they are not looking for a kill switch. That lever is also the jumper between the batterys to complete the 24V circuit. You can see that extra ground wire in the pic.

[John Mc]

Hard to tell what is going on there, since the cables dip down out of sight. The only reason I can think of to have an extra wire coming off between the two batteries is to provide a 12V power source. If the previous owner had no 12V accessories, perhaps they were using it to feed 12V trailer lights or a siren or flashng emergency light, or something like that?