Battery won't hold a charge?

[sarfu]

Hi,
I am thinking of purchasing a 1972 series III, one issue the truck has is something is draining the battery, owner has installed a shut off switch on the battery.
Should I be concerned or is this a commom issue and any ideas on what might be the cause?

Thanks,

Andrew

[Les Parker]

The Series wiring is not that complicated, so it should not be a serious problem to correct.
It could be a bad alternator diode allowing the battery to drain to ground.
Is the ignition light on after the key is turned off? The above would apply if this were the case.

[sarfu]

Don't know at this point, I have scheduled an inspection.

Thanks,

Andrew

[scott]

When inspecting, if you don't see the ign light on with the switch off, look to see if icomes on with the switch turned to on. If it doesn't then the ign light is out/disabled and you could have that bad alt diod w/o the tell-tale sign that les pointed out.

And if you just use the bat shut off switch eventually, during a drive, the drain or short will present itself in the form of a grey wisp of smoke

[sarfu]

So if it is as you say, a bad alternator diode, replacing the alternator would correct this problem. Hoping that is all it is.

Thanks,
Andrew

[Rineheitzgabot]

I have this same problem and have installed a battery shut off switch for convenience.

The drain is very slow. Some day, I would like to fix. Is it possible to install a diode, in-line, on one of the wires that is draining back to ground? Or should I say, would it be effective?

Anyone's input would be great, and help the OP and me.

Thanks,
Gary

[bkreutz]

One quick way to see if the alternator is the source of the draw is to unplug it and then see if the battery goes flat, If it doesn't, then you've found the source of the draw.

[scott]

d/c alt from the bat and let it sit, good idea. i'll use this as i like tests that give me plenty of beer time