350B Voltage/Batteries

[Jack-the-Ripper]

Just some general thoughts for those timid about electricity.

I use jumper cables for quick temporary test connections like those suggested here.

I made some extra heavy ones for truck and tractor use - I came across some very large fine strand wire and bought large hardware store clamps. One could buy some lengths of welding cable for the same purpose. Size 1/0 or 4/0 should do nicely.

Note wire sizes go up as the number goes down, so this series goes from small to large: 14, 12, 10, 8, 6, 4, 2, 1, 0(or 1/0), 00(or 2/0), 000(or 3/0), 0000(or 4/0). The zero sizes are often pronounced "ought" (or "aught") like in "naughty" or "ought to have been." I've never checked the spelling. So you will sometimes hear size "one ought" or "four ought" for example. The cheapest battery auto store cables are size 8, or even worse, size 10, aluminum (Ugh!). Always buy copper cables, whatever the size, and before using them, solder the wires to the clamps for lifelong low resistance. If you can find copper, instead of copper plated steel clamps, so much the better, although I don't know if copper clamps are even made.

Years ago, I installed a "bad" rebuilt starter in a car, and had to do it all over again. Since then I always test them first, before installation (new, rebuilt or repaired) by connecting them to a battery using my jumpers, on the ground where they can't jump off the bench. There will be a spark when touching the clamp to the post. Don't be timid and don't touch the threads, but rather the post end, as the spark can ruin the threads. Even better, clamp onto the post, and touch the other cable somewhere on the starter frame to avoid this problem altogether.

Once started, the diesel should only need electricity to hold open the fuel solenoid. If the alternator does not have a readable voltage label, you should be able to start the engine (even at 24V if necessary), then carefully remove a battery cable (for safety, only the ground or common one that connects to the chassis) and measure the voltage at the alternator output (assuming she's still running with the solenoid held open by the alternator's output) - it should be more than 12V, closer to 14V, (which is also how you check an alternator or other charger in any battery involved system, except normally you don't need to remove the battery cable). A 6V system should read about 8V while charging, 24V system 28V, 48V system 56V, all of which also applies to solar, hydro and wind systems as well as vehicles.

I agree with others that a compromised ground path is the most likely culprit. You could also test the ground path by measuring the voltage directly across the starter while you are cranking the engine. If the 24 volt battery setup is only measuring 10 to 15 volts at the starter, you know you have a high resistance ground path, and should clean all the connections in the battery return path (and even coat any steel surfaces with the anti-oxidant used for aluminum wiring if you want).

If the batteries' voltage remains at 24V instead of going up to 28V while running, that would also indicate that the 12V alternator is not capable of charging the 24V battery combination.

I think it is very unlikely that the machine has been converted to 24V. When trouble shooting, sometimes our brain will subconsciously make such assumptions rather than facing the uncertainties of having to go through the whole troubleshooting process which might otherwise appear to feel intimidating.

Let us know if 12v eventually works out.