89 Yj charging issues

[Mudgrunt]

89 YJ  4.2 I6
amp gauge jumps around between 8 and 14 runs at 14 for awhile then moves down a little then back up to 14 then drops to 8 and then will move back up. I pulled the positive cable off the battery to see if alt. was working and the amp gauge went to 14 and the idle of the engine smoothed out. Put cable back on and gauge dropped down and engine started to idle rough any ideas what causes this.
Thanks in advance for your help.

[Chevy Racer]

Regulator is going bad.

[4x4xdodgeman]

battery is going bad, if you have a different battery put it in and see if it dose still. cause if it was the regulator it should do the same thing all the time.