Big 3 Help

[adriver]

The NBS alternator has an external voltage regulator at the battery clamp starting in 2005.

 

[adriver]

I just installed the big 3. My voltage is definintely raised but it fluxuates. Between 14.4-15.0 or around that. Is this normal or is something wrong?

Can you be more specific? Does it have an aftermarket alternator? If so you will want to verify on there website. I have a 300 amp mechman that stays right at 14.8v (which is right at where there website says it should be). You're not too high at all, that's right where you should be, but the fluctuation could be a problem. What year?

What kind of alternator do you have? (amperage and brand)
When does it fluctuate, when idling, when driving, or depending on the RPM? (If you got a cheaper rebuild you might have a low (even lower than factory) amperage output at low RPMs. Some of the cheaper alternators will just have a really low amperage output at lower RPM. Could you be trying to draw too many amps at a low RPM and fluctuating voltage?

 

[HiHoeSilver]

that's weird thought they didn't start that till 07

I found where I asked before. James said no, but a couple posts down, Jason had some insight but not sure. I don't think I ever actually went looking for it in my truck, either. If I did, I don't remember, but my gauge sure acts like it does.

https://www.tahoeyukonforum.com/threads/useless-information.97483/page-29#post-1242922

The NBS alternator has an external voltage regulator at the battery clamp starting in 2005.

This might make sense. I wonder if e-fans had anything to do with it?

 

[Chrismnj]

no

I thought I read a post on here and nbs had external voltage regulator.

 

[Chrismnj]

I thought I read a post on here and nbs had external voltage regulator.

edit,

I guess too late you guys figure this out already. lol

 

[HiHoeSilver]

edit,

I guess too late you guys figure this out already. lol

I think what @adriver said makes sense. A few things changed for 05-6, including the fans. Maybe the RCV was part of that, too. I'll look closer this afternoon to refresh my memory and report back.

 

[Doubeleive]

even if so the op's truck is a 03

 

[HiHoeSilver]

even if so the op's truck is a 03

True dat. Good advice to check all terminations regardless.

 

[Chrismnj]

OP should test batter and alternator at local auto zone or other store, definitely load test the battery

 

[CJ Rodarme]

It’s a 150 amp, I think from the 3500 6.0 trucks. So it’s more than stock but its still OEM. My bet would be that it’s the battery. It’s old stock and I’ve beat on it. I’m resting at about 14.6, maybe a little higher. It’s at 15.0 ish when I first start it. I’m not concerned with where the voltage is but it’s the fluctuation that I’m concerned with. My best bet is the battery.