Working on 85 ex military 6.2L pickup. Installed new starter and batteries. When I try to hook up the batteries the terminals arc and it sounds to me like the starter solenoid is engaging. I lowered the steering column and unpugged the black connector from the ignition switch. Now when I hook up the batterys the problem goes away. Where do I need to look from here? Is it common for the ignition switch to go bad and cause the starter solenoid to stay engaged?

You could look at the starter, there should be a wire coming from the ignition switch to the starter solenoid. I'd guess that 24V on that wire would energize the solenoid. If you have 24V on it all the time, it will probably be the ignition switch.

why would there be 24V?

military vehicles are MOST often a 24v set up...not always but most of the time...

Since you mention it, it might be 12V because the cabin gets 12V? But it's a 24V starter, if that hasn't been changed ...

It is still 24V system. Starting/ charging system is 24V. On the black connecter going in to the ign switch which wires are for the starer solenoid? Where can I find a wiring diagram?

There is one here: http://www.dieselplace.com/forum/attachment.php?attachmentid=60120&d=1205337686

Found starter relay under dash with contacts burned together. Replaced. 1 week later probably 20 starts the new relay does the same thing and welds the load contancts together. I can only think that excessive current is being drawn through this relay. What might cause this?

Olee- I did not find a section with a wiring diagram in the above link.

Oh, sorry, I was just assuming that the service manual has wiring diagrams like the one I have. Google for "tm9-2320-289-34.pdf", that's a service manual including wiring diagrams.

You are right about the excessive current. Maybe you got a 12V starter that gets 24V supplied? Other than that, there are great differences in the quality of relays. For how much current is the relay you are using rated?

Thats the trouble, I know I have 24v at the relay, but I'm not sure if I am supposed to. My GM dealer can't seem to tell me anything. I asked if the relay was 12 or 24 and the parts guy said he didn't have that information. The new part number is the same as the old one, and they look exactly the same on the outside. But, when I remove the metal cover from the relay they are designed different internally. Now that I think about it the contacts inside the old relay look heavier than the ones in the new relay.

If you got a relay at the gm/chevy dealer. it is 12 volt.

:iamwithst Try NAPA... explain you're prob to the old guy (they usually have a clue) they have a pretty wide selection of "different" relays. 12 volt control side, 24 volt duty side.

You could use a Ford starter relay ...

Tried NAPA. No good. I could do the Ford starter relay thing but I may risk damaging someing else. Kind of like sticking a 40a relay in the 15a slot.

Tried NAPA. No good. I could do the Ford starter relay thing but I may risk damaging someing else. Kind of like sticking a 40a relay in the 15a slot.
So put fuses in the relay circuits if you are worried about them. Even though the starter is 24v, all the ignition ciruit is doing is powering the solenoid of the starter anyway, and solenoids are not amperage hungry.

Here's a thought. What if I'm getting a bad ground on the control side of the relay and it is not energizing the magnentic coil enough to make the contact points clamp together and make a good connection. Instead they arc each time the relay is energized and evetually the contact points weld themselves together. I'm thinking that I should trace the ground circuit for the control side of the relay.

Here's a thought. What if I'm getting a bad ground on the control side of the relay and it is not energizing the magnentic coil enough to make the contact points clamp together and make a good connection. Instead they arc each time the relay is energized and evetually the contact points weld themselves together. I'm thinking that I should trace the ground circuit for the control side of the relay.
Thats a possibility...I would load test the power and ground of the control side.