Military Vehicle Repair: m1010 cucv electrical problem, battery isolator, volt system

Question
I have a m1010 cucv ambulance that, for some reason, keeps draining the front battery and killing the 24 volt system. The m1010 will run great for weeks then, out of no where, the battery charge is not enough to start the engine. Any ideas to fix this problem are greatly needed.Thanks. Bob

Answer
Hello Bob,
The front battery operates everything on the truck except the starter. The starter is the only 24 volt item.

It is possible the battery isolator or voltage regulator on the left front fender liner is bad, but those are quite expensive.
It is also possible that the blackout lights are on, or the blower switch under the instrument cluster.
With everything quiet, operate those switches, and see if you hear a relay click under the dash.
And check those blackout lights, prefferably in a real dark area.

Van