So this just started the other day it seems that after it warms up the Battery gauge drops to nothing went to autozone and check the battery and alternator and both came back good so then i drove to oriley 20 miles away and same test both good again??? Any ideas? 2000 jeep cherokee sport . thanks guys

 

Start by checking and cleaning all of the grounding points. Which include both battery terminals, battery to fender, Oil dip stick, rear of head to the firewall. Also the mounting surface between the starter and the engine block. While you have the starter out you should that also bench tested. I just replaced my starter because it was causing the same problem on my 98 XJ.

 

could be lots of things. I'd check the voltage to the back of the gauge and watch to see if there is any drop when the gauge changes. If so, then you have a problem either in the circuit, alt / etc. If no drop on the digital volt meter when the gauge changes, then the gauge is going.

 

well got it all figured out it! it was the alternator i guess it was just dieing slowly! got it replaced and all is good! thanks for the help guys.