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Discussion Starter #1
Been dealing with a high voltage problem for a while now. Truck will start fine, volts will be at 14.6 and climb to 14.9 or 15.2 and stay there, no matter what I do.

From what Ive read, the Generator Battery Control Module (GBCM) is supposed to be in charge of the alternator's output. I don't have any DTC codes and alternator and battery are good.

Ive disconnected the module and im at the 13.8v default (It's supposed to do that) but Id really like to get this fixed. Anyone ever have a similar problem?

Battery is new and Ive swapped my DC Power 300XPS for a known good oem unit, no change between alts.
 

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Update:

Replaced the GBCM with a good, working unit, charged the battery, disconnected all my big 3 wiring, amps and dash camera. Problem went away. I'll be adding back one wire/component at a time until I either recreate the problem or I get everything back on.

OEM neg battery cable has ZERO resistance end to end and wasn't corroded or anything. The only corrosion I found was inside the amp 1/0 lead from the batt terminals to the fuse holder. Before disconnecting the wire, I read the voltage at the amps and it was 0.20v lower at the amps than the battery, not bad imo.

One of my big 3 ground wires had some resistance, but was like .02ohms...nothing major.

Will keep updating as I add stuff. When I was looking for info, I found a lot of people had this issue, made a thread and never updated :pissed:
 

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Update:

Replaced the GBCM with a good, working unit, charged the battery, disconnected all my big 3 wiring, amps and dash camera. Problem went away. I'll be adding back one wire/component at a time until I either recreate the problem or I get everything back on.

OEM neg battery cable has ZERO resistance end to end and wasn't corroded or anything. The only corrosion I found was inside the amp 1/0 lead from the batt terminals to the fuse holder. Before disconnecting the wire, I read the voltage at the amps and it was 0.20v lower at the amps than the battery, not bad imo.

One of my big 3 ground wires had some resistance, but was like .02ohms...nothing major.

Will keep updating as I add stuff. When I was looking for info, I found a lot of people had this issue, made a thread and never updated :pissed:
Did you run your big 3 through the factory sensing ring?
 

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Discussion Starter #4

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Discussion Starter #6
I'd be willing to be that's where your problem lies.
:shake: ill put it through the loop....it never occurred to me that that could be the problem but once I started reading into what that lil box does, I figured it was something in my wiring or that box.

The more I deal with this electrical, the more I just want to run an independent charging system...its what Anthony @ DC told me to do from the get go :facepalm:
 

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I'd be willing to be that's where your problem lies.
My truck was charging fine this morning I put the ground through the loop and I went up to 15.2. Never charged that high ever. I then yanked out big 3 ground totally from the truck. Let truck run for 10 minutes and voltage went back down
 

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So i pulled out the stock ground on the block. Ran a single 1/0 through the ring sensor to the alt GND bolt. And so far I'm good. Let the truck run for 15 minutes then I drove another 20. I stayed at 14.6
 

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Discussion Starter #9
I'll be doing that ^ this week. My voltage has been fine ever since I went back to oem wiring and want to keep it that way.
 

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Discussion Starter #14
Update:

Hooked up my amps on friday, drove friday/saturday and it sat on sunday for half day. Volts were always sub 14.6.....turned truck on this morning and shot up straight to 15.2v again. Drove 20mins to work and never went back down. Im thinking the amps have something to do with this and will remove one n see if it goes away.
 
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