Quote Originally Posted by hippieman9 View Post
Well, The Battery light will come on at highway speeds. A/C on, and I have the latest DMC Alternator on the car too.
Since it does it at highway speeds, it's probably not the RPM/pulley. That leaves adding the diode (good bet when running late model alternators).
OR, you could have an intermittent short/drain, probably in the AC/Cooling Fan electrical system(s). If a diode doesn't work, hook a good voltmeter up and watch the readings as close as you can for more clues...


EDIT: Should of asked before- You say the light flashes on only when the AC was on. Before/After/??? it started blowing warm air?