jeaux

when I'm driving at night low idle with a/c on lights get dim alt. good battery good I even changed ground wire on battery any quick checks?

wombvette

Normal.

ACECO

Well yes, to a point. However it could also be a sign that your alternator is getting weak, or perhaps a shorted diode, and is not putting out as much juice (if any) at idle as it could. Also could be that the battery is also getting old and with the high amp draw with the lights, AC, etc on it is dropping down in voltage further than it should when the alternator is putting out little current at idle.

You could always have them both tested to see if either of these is the issue.

Good Luck!