Starter mystery

[bigeasy]

Ok so the starter went out on my old 24 volt military 6.2
I replaced it with a starter i had lying around. Must have been a 12 volt because it only lasted about a month before it died / melted the main link from solenoid to starter in two.
So i ordered a "new" 24 volt starter. I installed it. Nothing not evens a click from the solenoid. So i get out to see if i overlooked something; to smell plastic burning, see smoke from starter area, and find the solenoid to hot to touch still melting down with the key off. Had to pull the battery connection to alleviate the problem. I take it off and it has melted the solenoid down internally.
It has been working the way it is wired for about three years before initial starter failure.
So my question is: Do i have a problem or just dumb luck lately??
One starter died / two melted down.
I have noticed a lack of a real good ground from batteries to engine block.

Also why is it wired in series twice?
The first battery runs to the second and then to the junction block; and there is another wire from the first battery to a lower junction block with a joining strap to the other junction block. Redundancy? or is there not supposed to be a jumper from one block to the other. Making one block 12volt and the other 24 volt.

Sorry for the long post

[ccatlett1984]

first off for your military questions i recommend that you come join us at steelsoldiers

the front battery positive goes to the rear battery negative and connects to the upper buss bar on the firewall (thats the place to get 24v positive)
the black wire that goes from the lower buss bar to the negative on the front battery is a ground. the little wire that is between both buss bars is a suppressor for the radio equipment that was used on the trucks.

i would replace the starter relay thats under the dash on your truck. its right above where the large round diagnostics plug is, its bolted to the bottom of the dash. its a silver rectangle and is known for having issues. you can get a replacement at the local parts store, ask for a AC40 relay. the original relay only has four pins, the ac40 has five, but the extra pin is unused and wont make any difference in the operation of the relay.

once you replace that relay, be sure that you only have power to the purple wire when you have the key in the start position, not run. test this before you hook up the starter. then hook up the starter and give it a try for added safety you can install a high amp toggle switch inline on the purple wire, that way if the relay were to fail with the circuit closed, you can just flip the switch and save your wiring.