Grounding

[KO1927]

I am new to the old truck hobby and have a 1952 Mack LTLSW with a Cummins Engine. It has not been run in 6 years. I would like to know if it is positive or negative ground so I can connect the batteries (two 12 volts with 900 CCA's each) properly. So far, if I hook them up either way (positive then negative and vice versa) there is significant sparking between the connections as they try to arc-weld themselves together.

Thank you,

Ken

[truxnut]

You may have a series/paralel switch on that truck for 24 volt start. 2 ways first see if there is a tag on the starter and see if it gives the voltage ,they normaly do. Next trace the battery cables to the starter and see if you find a big solinoid looking thing, if so that is a S/P switch. As to ground it can be either ,most big trucks were positive in those days . Does it have a generator or alt.

[KO1927]

It has an alternator. The I.D. Plate on that says 14 volts, 105 Amps

[Freightrain]

Sounds like someone already upgraded the electrics? Does the truck have any kind of radio in it?? This would confirm they switched to neg. ground(most likely).

It also sounds like there is a serious short issue if the battery cables are arcing trying to hook them up. With the truck shut down, you should be able to hook the batteries either way and not see a spark. Now, if something on the truck is shorted, somehow, then it would cause sparks when hooking up the batteries.

Time to do some investigating, trace the battery cables, check the wiring and see if something is crossed somewhere.

[truxnut]

The charging system is 12V [14 rating on Alt.] , you still can have a S/P 24 vo;t start. Trace the battery cables ALL the way to the starter. If you find a big solinoid looking thing between the batteries and the starter solinoid you have a S/P . See if you can find a tag on the starter ,that will show if it is 12 or 24. S/P systems can be wired either pos or neg. And another thought ,the starter my be shoeted out. Dis-conect the cables at the starter and see what happens.