fluctuating gauge

[CHIEFSONN]

Can someone tell me what might be doing this.one of the first things I bought for the truck after I purchased it was 2 850 cca batteries from Coastco interstate. The truck is on a trickle charge when sitting and the power is disconnected before starting, when turning the engine over the battery gauge drops from the green to the yellow,once started the battery gauge fluctuates and does not stay on or at the mark in the center of the green section.I thank you for your replys

 

[02smokemaker]

Check your belt tension first.
Then if not that it's probably the regulator.

Sent from my LG-LS997 using Tapatalk

 

[rtadams89]

This thread prompted me to finally check my belt tension, as my electrical system has been hovering around 24.2v all the time (even with engine on when it should be higher). I found the problem: both bottom mounting bolts on the alternator are gone; the thing is basically held in there by the belt. I'm actually slightly impressed that the alternator has been working at all for the last 500 miles. Tomorrow's task list now includes putting new bolts in and likely replacing the belts.

 

[02smokemaker]

Looks like you barely missed disaster!!
Exactly why I use loctite on all my threads. These engines have some GOOD VIBRATIONS

 

[rtadams89]

What actual voltages do the marks on the stock gauge correspond to?