Just put a new battery in my 92 XJ
Everything seems to work as it should. Starts like a champ, Headlights are bright etc .
In the morning when first starting Alt gauge is right of center.
Notice that when i drive it round town for a couple of hours -starting/ stop engine. the Alt gauge moves left of center slightly when driving.
When revving engine it barely moves at all.
As stated above starter cranks great and no dimming of lights is seen.
What is the test with a Volt meter to see if the Alt is charging at all ?

 

Should be above 13

 

Get a multimeter. Use 20V DC range unless meter is autoranging. Place the red lead on the pos. terminal of the battery and the black lead on the neg. terminal of the battery.

If charging system is good and battery is good, at a high idle, you should be in the 13.5 - 14.0 volt range, give or take a little.