GREENSIERRA

I am having a issue on my 05 sierra where the battery light is on and the volts sit around 13.2-13.5 with the truck running, i have tried 2 new alternators, new battery and also a known good battery from my 05 Tahoe.
if I unplug the 2 wire connector from the alt it doesn't change anything.
the truck does have terminator x integrated into the factory computer, alternator, starter, fans, fuel pump are all still running off the stock computer.
before I go tearing back into the factory wiring does anyone have any suggestions on what I could try to fix this issue?

Thanks, Mitch

strutaeng

Has it ever ran good before? Or this issue showed up after modifying the ECU?

I didn't know you could use 2 computers in this arrangement, but I had never wondered that...🤔🤷


I recently had an issue on 06 Suburban where my voltage stayed pretty low. With everything electrical ON, voltage dipped to like around 9V. My alternator duty cycle never ramped up. I was starting to think my ECU was not commanding the alternator to charge (had that problem on my wife's 3.6 Chrysler minivan before). With everything OFF, voltage was barely over 12V. But I replaced the alternator and that was the problem for me.

Do you have a way of monitoring alternator duty cycle %?

wretched73

iTrader: (1)

Did you upgrade your grounds?

GREENSIERRA

I run 0g power and grounds for everything
Should unplugging the 2 wire connector eliminate any wiring issues or no?
I hate wiring
Lol

smokinlmm

Have you checked the voltage with a meter or are you going off the dash?

GREENSIERRA

I have checked at the alternator and battery with a multi meter.
I am pretty sure my answer is going to be pinning all the grounds back into the factory computer incase i accidentally cut a ground off that is needed.
I did change every harness in my truck from a donor truck while chasing a issue for the past 3 years, I thought maybe my factory harness had some issues from having the motor in and out so many times and also doing a frame off. This donor harness could have a issue with it.
I have even changed the factory computer with a spare I have to see if maybe a driver was bad causing this voltage issue but it didn't change anything.

smokinlmm

Run a ground from your alt mounting point to your negative ground and see see if it changes anything. Sounds like you have a ground loop or are bleeding positive voltage into your ground.

GREENSIERRA

I have a zero gauge wire going from my alternator mounting bolt to the negative on the battery, I also have a 0g going from the alternator to the positive on the battery.
I still have the factory wire from the alt to the factory junction block that then runs to the battery, if I take the 0g wire off and just leave the factory wire connected the volts drop to high 12s.
this is all tested with a multi meter

smokinlmm

I’ve seen aftermarket led lit switches cause issues like yours. The led slightly shorts out and leaks voltage into the ground.

GREENSIERRA

I just took all the factory grounds off the other day and cleaned them all, I should check the resistance on them.
I don't have any led lights but I can check all my aftermarket grounds, I haven't checked those yet