Battery/ Alternator???

[powerstrokin999]

I have an 03 6.0 with 121000 Everything runs fine starts fine, it just when I mash on the gas the battery charging system light flickers on and off. When the truck wasnt running the batterys were at about 12.5 V with it started it was around 14.8.. Im wondering if it is the alt or the Batteries

[powerstrokin999]

and I did them one at a time..

[Chris4x4gill2]

14.8 shows your alternator is putting out the correct voltage.

12.5 on the batter is low - just over half charged. Full charge should be 12.7v and half charged is 12.4v

[powerstrokin999]

so im still researching... do you think it could be a loose ground wire? Im also having problems with the right turn signal and the heater fan?

[powerstrokin999]

so im still researching... do you think it could be a loose ground wire? Im also having problems with the right turn signal and the heater fan?

[Lilpooh]

First start checking your battery ground cable connections, especially the one coming off the pass side that gets grounded to the front of the engine block. Be sure your grounds are clean and tight. Next check the exciter wire on the back of the alternator, be sure it's got a good connection.

Have your batteries load tested seperately, you may have a bad battery.

Have the alternator load tested, it might be a bad voltage regulator.

A weak or damaged battery can cause all kinds of funky issues with our electrical system.

[powerstrokin999]

ok will be doing that tonight.. do you know of any known issues with right turn signal or the heater fan?

[Lilpooh]

A bad ground or bad/weak batteries can cause many issues, they may be related.

I had that ground cable on the pass side engine block come loose and caused my aftermarket EGT gauge bouncing all over the place.

Start with the basics, check/clean all connection, wire harness damage, load test batteries and alternator.

[Chris4x4gill2]

It sounds like weak batteries. I would put them on a charger andv from thalternator recheck voltage after they sit and normalize a while after charging. If you get less than 12.7 they are getting weak. Having them load tested at a parts store might tell you something, but that's usually only about a 100 amp load....much less than cranking demands of these trucks.

You may have a bad or loose chassi ground, but the neg battery cable should be ok if your getting 14:8 v from the alternator