Dim headlights with a\c

Sorry, I tried "search" but no luck. This is an 88 6cyl. auto. The voltmeter reads between 13 and 14 going down the road with headlights on but when I turn on a\c it drops to around 10 or 11 and the headlights dim. Is it a bad ground or should I be looking at a higher output alternator? Mechanically inclined, not an electrician but own a multimeter.

Check grounds, but also make sure the belt is tight. The serpentine belt on a 4.0 must be very tight indeed, and it may seem adequate when it isn't.

Remember too not to rely on the actual voltmeter reading if you have the fan turned on high. It will drop when the fan is on high, but this is an artifact of the voltmeter wiring, not an actual voltage drop. When in doubt, always measure voltage at the battery.

The alternator should be up to the job, so I'd check for other problems first.

Thanks for reply. I have not checked actual volts yet but know the alternator is newer and is 105 amp. Will check grounds first.

Check all that stuff, but if your RPMs aren't dropping really low, I bet you have an alternator problem, well I guess that could also include the battery.