Is there an electrical schematic available?

[SFC Cobb]

Is there an electrical schematic online where I can get to it??

I have never understood the start sytem on these trucks. Supposedly the driver side battery is the start battery. If it is then why does the passenger side battery prevent the truck from starting if it is bad?

Are the batteries hooked up in series?

 

[saratoga]

The batteries are parallel (both + terminals and grounds are hooked together). It does not use one battery for certain purposes; they are both drawn from at the same time.

My truck started with one battery for a couple of days when my passenger side began leaking for the second time and I had to take it out... it didn't like it, but did start. IIRC it has to turn over at a certain RPM in order to start, which it may not do in your case if one of the batteries is weak to begin with.

 

[db9938]

Is this what you are looking for?

http://www.gmupfitter.com/publicat/bbmanuals.htm

 

[duratothemax]

the diesels simply have the two batteries wired in parallel. THe gassers are different.

They will start perfectly fine in the summer on one battery, even with the junk stock AC Delco battery. Ive been running mine on one battery all summer because the second battery wont fit with the big turbo in the way. I doubt it will start this winter though.

ben

 

[SFC Cobb]

Thanks for the info.

That link does have electrical schematics that I can find. Thanks anyway. The info may be helpful for other things though.

 

[RayMich]

The high compression ratio for the diesel engine makes it much harder to turn while cranking. The 2nd battery is wired in parallel in order to provide the higher amperage required to crank fast enough to start the engine.

They will quite often start on one battery when it's warm, but the cold weather will zap a single battery in no time.

 

[LtEng5]

dont forget about the amount of juice thats needed to run the glow plugs and IAH