Weird Voltage Issue

[moviewithnotitle]

Background:
1996 Tahoe 2dr. 5.7L, Auto, A/C, 4x4, Single battery.
My battery and Alternator are both good. Charging is right at 14volts when running. 12.6V with engine off. I have a Optima Red top that is 1yr old. I have a 105A alternator that is two yrs old. All wiring is clean (meaning no corrosion) on the battery terminals and in most places I check like grounds and connections.

Problem:
- When I turn on the headlights, the volt gauge on the dash dips a bit, and stays there.
- When I turn on the blower/fan, the volt gauge on the dash dips a bit, and stays there.
- When I turn on the the headlights and blower, the volt gauge on the dash dips a down alot, and stays there.
- When I turn on the headlights and the turn signal, the volt gauge on the dash will dip when in sync with the turn signal.

Conclusions...
1. I suspect this is a ground issue on a main wiring harness. I have corrosion or a bad connection somewhere that I don't suspect to be bad. I have done some due diligence on the grounds on the frame, motor, battery etc, but can't seem to find the root of the cause. All wires look good there too.
2. I don't suspect the gauge is bad, as it will read normal on an everyday basis.

Has anyone experienced anything like this or have a few thoughts about what might be causing this based on my descriptions?

Thanks,
MWNT

 

[94 Silverado]

Hey. My 94 does the exact same things. I haven't been able to figure out what's going on either. I haven't replaced the battery cables yet because the ends look good. I guess it could be corroded down in the wire somewhere. My battery, alternator, and starter are all about 2 years old.

 

[mjleg]

Me too. Same prob

 

[UrbanOffroad215]

i had this issue with my 98...turns out it was just the ground wire from the battery to the inner fender was corroded

 

[94 Silverado]

i had this issue with my 98...turns out it was just the ground wire from the battery to the inner fender was corroded

Was it visably corroded or did you have to remove it to tell?

 

[moviewithnotitle]

UPDATE:
I did the Big 3 grounds and also some other grounds over the weekend. I also upgraded the charge wire from the Alt. All issues remain as stated in the original post. (M%^$#@-F@*!#@). I am setup for the 2nd battery install though which is good.

I am hunting for some additional grounds and also going to temporarily setup an alternate Voltage gauge to see if it's not just the dash gauge being 14yrs old and tired.

MWNT

 

[mjleg]

Let us know how it goes.

 

[99z28monster]

mine does the same never even thought it was a problem.

 

[daddy_dandy]

Common problem with these vehicles. The headlights get their power directly from the switch which causes a big load on the system. My suggestion is to get some relays and wire them directly to the battery. Nothing you can really do about the blower. The turn signal jump is a problem with the circuit boards in the rear tail light assemblies. I've heard they fixed the boards and you merely need to replace them but I can't be certain that's true. One alternative is to get a set of LED tail lights- that will most certainly fix the problem. You'll need a new flasher too. The 105 amp alternator suck. Check out the upgrade to the AD244 thread. I got one from a junkyard off Ebay for ~$50. It's a great alternator and definitely worth the upgrade. Also, do upgrade the ground wires in the truck. It won't hurt.

 

[barebones 1500]

mine does the same thing. i am leaning more toward alternator cause when i checked it it only read 13 volts opposed to the normal 14+ volts