M923A2 battery/electrical issue

[Scott88M]

Lately my voltmeter has been pegged far right. It jumps to far right when battery switch is turned on. Before it would occasionally jump far right every once an awhile now its there all the time. Truck runs fine, all other electrical seems fine. I'm on a 2 battery system now because one battery went bad. Does this sound like a bad battery or alternator? Since it pegs before truck is even running I suspect a battery issue but I could really use some help. Thanks.

 

[Coffey1]

Have you checked voltage meter to see if it's overcharging.

 

[Scott88M]

No unfortunately my multimeter crapped out I need a new one. Would that make gauge jump as soon as the battery switch was flipped? I assumed since the engine wasn't running/alt wasn't spinning it was only reading the batteries. I did unhook 1 battery and gauge went to yellow, hook up second it pegs to far right don't know what that might mean.

 

[74M35A2]

Sounds like a 12V gauge in a 24V system. Check system voltage with a known good voltmeter as next step.

 

[Wildchild467]

I agree with the other guys here... check it with a multimeter and go from there. I suspect a faulty gauge but that is just theroy. if the voltage was too high you would be blowing light bulbs left and right. Your battery voltage should be around 26-28 volts I believe. The alternator has an adjustment on it to adjust battery voltage, but again, check with a known good meter. Checking battery voltage at your slave cable receptacle is quick and easy.

 

[74M35A2]

A fully charged "24V" wet cell conventional lead acid battery system should show 25.6V after the surface charge is removed. Anything higher than this is charging level voltage. The 26V-28V mentioned above is charging system voltage, not battery voltage.

 

[Scott88M]

I've had no problem with blown lights and the gauge had been fine the whole 6k miles I've put on the truck since March so I don't think it's a 12v gauge.