Voltage; guage looks low

[Camoman92]

excuse the dumb title. I have a 97 Powerstroke with 123000 miles. When I drive the voltage sits right past the R in normal. When I switch my lights it drops in between O and R and if I use my window the needle jumps down and back up. Took the truck to a buddy and tested both batteries; one threw a bad batt and a bad alt on one battery. So I replaced the battery. It Threw good codes after but the guage still reads wierd.

P.S. Doing a tri pillar soon so I wanna solve it before I put more drawing amps in it.

[BigFuel]

Originally Posted by Camoman92

Took to a buddy and threw bad batt and bad alt on one battery and replaced the battery..

Just not understanding this sentence.

[Camoman92]

sorry, I posted it before work so I was running late. I took the truck to a buddy and tested both batteries and the alternator. On one battery it threw a bad alternator code, but did not throw a bad alt code on the other; So I replaced to battery and no bad codes were thrown. The problem is still happening though.

[erics diesel]

i believe you should replace both batterys at the same time or the old one can kill the new one right away. and also check the big wire on the back of the alternator for corosion

[BigFuel]

^ Agreed. So with the engine running you are getting 14.2v at each battery?

[Camoman92]

I dont remember what the voltage said at my buddies but I have a multimeter that ill check again. I would set it on a DC setting right?

[Camoman92]

Originally Posted by BigFuel

^ Agreed. So with the engine running you are getting 14.2v at each battery?

I did a 12 volt load test and the new battery read 13.8V and the other battery read 11.3V. So I will replace the other battery. Since im doing a tri pillar should I consider a new alt anyway? I was gonna have a local shop rebuild and beef it up some. I have been reading about the ones from the auto shops and they dont seem to last very long. It would probably cost less for a rebuild and probably get a better warranty.

[BigFuel]

At night with the headlights on do they slightly pulse? Yes aftermarket rebuilds can be iffy and quality aftermarket custom ones can be expensive. Mine is $800.

[Camoman92]

They only flicker if I use my inside lights or windows

[BigFuel]

Flicker like pulse or just dim.