12 Volt vs 24 Volt question ..

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'70_Duster_340

'70_Duster_340

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I hope you guys won't mind an off topic question, but there's always someone here who can help..

I'm trying to get a big truck ready for sale, with a 400 cummins in it.. I can't get it to start w/o jumping the terminals on the starter solenoid..

Three of three batteries load test fine.. Here's what I think might be the problem, but don't know.. We changed the solenoid on the firewall, but it's a 24 volt solenoid.. Parts guy, who is usually pretty good, said it should work.. I cleaned all the terminal ends and replaced a couple going into it, grounded it well, and even took the main ground from the starter off the firewall, sandblasted it bare and re-grounded it.. All I get is click click click when I push the starter button after turning the key on...Everything seems hooked up and connected well..

Any ideas ??

Thanks,

Kenny
 
if you have a 12 volt charge/run system on the truck it will not work. you will need a 12v starter solenoid.
 
Correct me if I'm wrong but you said that you've got "three" 12 volt batteries that should be connected in parallel and therefore your starter is also 12 volt but check to be sure. Therefore you need a 12 volt solenoid. Some of the old big diesel engines used a 24 volt starter and the "two" 12 volt batteries cables all went to a what was called a PSP solenoid (parallel-series-parallel) that was sometimes located on the wirewall. When you went to start the engine the solenoid would switch so that the batteries were in series giving the 24 volt starter what it wanted and when you let off the key the solenoid would switch the batteries to parallel for 12 volt charging and handling loads like lights. A lot of the big diesels now have gone to 12 volt starters and the system uses three 12 volt batteries in parallel and the PSP solenoid is not required. Essentially the parts guy may think you've got a 24 volt starter.

Terry
 
Yes Terry, the 3 batteries are hooked in parallel, and the starter is 12 Volt. Also, the solenoid I took off the firewall was stamped 12 Volt and probably original to the truck, so I'm guessing I just have to get a 12 volt solenoid ? The truck is an '84 Diamond Reo Giant..
 
Thanks guys, as always, you've pointed me in the right direction .. As soon as the weather clears up at the tail end of the week, I'm gonna get a 12V solenoid and will let you all know how it works out...

Thanks again,

Kenny
 
Just a follow up ... Installed the 12V solenoid relay today and she fired right up.

As always, thanks so much to you guys for chiming in, it's greatly appreciated.

Kenny
 
Thanks Tracy .... Now I just gotta sell off a couple of these trucks that have just been gathering dust the past couple years .. I hate selling stuff, but gotta lose that farmer mentality of mine, or everything is gonna just sit on the "back 40" and rot into the ground !!

Kenny
 
I was like that too when I was young cause my grandma had a nice big place in the country that I could put anything. More than once stuff just sat there and rotted. Some of which I had offers to sell and turned them down.:angry7: Live and learn.
 
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