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sparg93
04-02-2012, 06:30 AM
I have an issue that I'm running out of ideas on how to fix...!

My resting voltage is 12.4 and when I start the truck I'm at 14.5....however, as the truck runs, it slowly drops down to 13.8. When the truck cools down and I restart at a later time, it starts @ 14.5

If I'm driving for awhile, I've seen it hit 12.* volts.

I have a OEM 140amp alternator that I've had bench tested and it passed all their (Advance auto) tests. I also just installed a new 220amp and it passed as well...and the voltage dropped just like the 140amp!! Even if everything was turned on, my only big draw is my efan (mark VIII) and 1500watt (draws 60amps @ max) sound system.

I've turned off all accessories, lights, etc and the exact same thing occurs with the dropping voltage; so I know I'm using nowhere near the alternator's capacity. The battery is grounded using OEM + 0gauge wire to the body and the alternator is wired using OEM + 0gauge wire. The battery is also a dual post Interstate that is <1yr old.

Thinking their might be a bad ground from body to frame, I bought a big grounding strap and through bolted it on each side....no improvement.

Any recommendations to fix this??

vegaman04
04-02-2012, 06:58 AM
Gonna need specs on your truck to address issues.

sparg93
04-02-2012, 07:03 AM
Gonna need specs on your truck to address issues.

1999 Tahoe (OBS) 4dr 4x4 - 5.7L

AJAMES07
04-03-2012, 04:12 PM
i had some serious dropping with my voltage and the reason it was doing that was because the fuel pump was shot. check your fuel pressure etc. that solved my problem 100% and no i am always at 14 volts even when my 2 12's hit on stock alternator

sparg93
04-03-2012, 09:42 PM
I'm not sure if that's the issue, but it's definitely something for me to check out!

Any other ideas folks?

vegaman04
04-04-2012, 10:55 AM
Did you clean the ground point locations?

sparg93
04-04-2012, 07:47 PM
Did you clean the ground point locations?

Yes.

A few guys said the truck is acting normally with the voltage decrease...but I'll keep watching it and unless it dips to <13 regularly I've been told its Ok.

Supposedly b/c I have such a high power charging system and the load on my truck's electrical is so light, my alternator rarely turns on.