I have a Dodge Ram 3500 Diesel 2004 truck 1 ton truck. The Check Gage light comes on and the battery gauge stops working when the light comes on. I checked all battery cables and they are tight. The serpentine belt has just been replaced a year ago and still looks good. The alternator has been rebuilt appx 2 years ago. Any thoughts on what else to check? BTW, the light will go off periodically but for the most part - it's on. The battery indicator gauge is definitely related to this light. Thanks in advance for any tips

 

Take the alternator off, and have it tested. (preferably under load)

If the alt tests good, then the regulator is failing.

Moving to third gen Ram section as well.

 

Thank You!