odd charging problem??

[off_road_junkie21]

Ok my truck has done this since ive had owend it. When u start the truck the amp guage is ok. But once it has been running for a while the guage starts jumping tword the postive side And back. Ive cleaned the battery cables 3 times and it still does it. Then about last week i went from a 40 amp to a 80 amp alt. So now it does this really bad. What is this?? By the way this is a after market guage. Thanks shaun

 

[off_road_junkie21]

Anybody??

 

[martin]

How is the gauge wired in?

 

[off_road_junkie21]

I belive hot to guag then to ground