Factory dual battery wiring

[Daveo91Burb]

A few weeks ago I checked this based on the RPO code sticker in the glove box and came up with a factory 105 amp alternator. Does that seem correct as an option for a '91? Of course some PO could have replaced it with something less - I'll have to check a little deeper to make sure


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[HotRodPC]

A few weeks ago I checked this based on the RPO code sticker in the glove box and came up with a factory 105 amp alternator. Does that seem correct as an option for a '91? Of course some PO could have replaced it with something less - I'll have to check a little deeper to make sure


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Very possible it was downgraded if replaced. Probably the only way to know for certain is an amperage output test and to do that I'm pretty sure you have to jump the prongs so that the voltage regulator is bypassed so it the alternator will do a max output. But don't hold me to that, read up on the test before you jump anything so you don't trash the alternator or the regulator.

BUT, IIRC, the 105 amp had a different plug than the lower output alternators, so if he kept the same plug and didn't modify it, then you'd know. That stuff is all foggy to me now, I'd have to check for sure, but I know all of the above can be done.

 

[Daveo91Burb]

Very possible it was downgraded if replaced. Probably the only way to know for certain is an amperage output test and to do that I'm pretty sure you have to jump the prongs so that the voltage regulator is bypassed so it the alternator will do a max output. But don't hold me to that, read up on the test before you jump anything so you don't trash the alternator or the regulator.

BUT, IIRC, the 105 amp had a different plug than the lower output alternators, so if he kept the same plug and didn't modify it, then you'd know. That stuff is all foggy to me now, I'd have to check for sure, but I know all of the above can be done.

All the wiring at the alt looks original so I'm pretty sure I'm OK. If I ever have to replace it I'll make sure it's 105 amp. I did a quick search on Amazon for "Alternator 1991 V2500 Suburban" and mostly 105 amp units came up. And the others were 95 amp so not too worried. I have faith in my POs - the guy I bought it from was a car guy, too.

 

[Craig 85]

Does anyone have a diagram for an '85 dual battery set up? After seeing this post I think my truck is missing a couple of parts.

 

[kickdeez]

This is a great thread. Just stumbled across it this morning while perusing. I have a dual battery setup in my suburban. I am currently dealing with a few electrical gremlins, and I'm fairly certain they are battery related. I know my batteries are older, so I plan to replace them, but I also suspect that the dual battery setup was not wired completely correct by the previous owner, so I plan to dig into that as well. This thread will help.

 

[bucket]

I've had 2 with factory dual batteries. Neither with an original engine, but neither truck had that relay setup. Who knows what they had originally. They are just wired in series and it works great.

 

[Craig 85]

Just to add a little to this thread. There are two styles of relays for the factory set up. My '85 has a different style of relay than what was shown at the beginning of the thread. I had purchased the round style (right side of picture) as some of the wiring in this area had been chewed on by rodents prior to my purchase.

Well, it turns out mine has this silver box looking relay in the middle. The odd thing about this whole set up is the wiring is only 12 ga.! It won't make a difference on my truck, I'm not adding any accessories with a big power draw. Most of the aux lights will be LED.

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[Keith Seymore]

Just to add a little to the addition to this thread:

There were two dual battery setups from the factory: there was the dual setup for diesels, to help with cranking, and there was the dual setup for campers and auxiliary power (RPO TP2).

TP2 was available free expression on the pickups but not available on Blazer/Suburban as an RPO; there was a comparable SEO (aka "Specialty Equipment Option", like a COPO) for Blazer/Suburban but the alpha numeric code escapes me.

Back when I left the assembly plant and first joined engineering Roger B Smith (of "Roger and Me" infamy) was president of GM. His minions dispatched me to Flint Assembly to gather up all the parts so that they could add a second battery to Roger B's Suburban.

K

 

[00cls1camaross]

Does anyone know how to download these wiring pictures so you can see them? They are too small for me to read.

 

[HotRodPC]

Maybe someone else has these pics and can upload them in bigger size. That appears to be the full size image posted. I can't read that either. I just thought about it, I wonder if they can be printed bigger and legible.

 

[Raider L]

@HorRodPC,

When the format was changed, now I can't copy pages like the schematic for the duel battery set up, like I could before for references. Is there schematics on this forum like @chengny was showing? I used to be able to copy images and can do a couple, but this all could be due to my old operating system. Most of so much these days is geared for Win. 8 and higher. I've been wanting to do a double battery change for some time and am trying to amass as much about it as possible because I'm dumb, dumb when it comes to electricity.

I could see the schematic but the print is so tiny I couldn't make out what it said. So, I tried to copy them and blow them up but the print just got worse.