Okay, I have been searching and can't really find anything on this one so I am reaching out. I have an 06 MCS where the voltage is dropping to 12.0v when the AC is turned on at idle. Once you tap the gas it jumps up to 13.5 volts and if you are moving it is fine. I thought it was the voltage regulator that might be going bad, so I put a new alternator in but that did not solve the problem (still needed to be swapped as the other had 99000 miles on it).

Any thoughts on why the AC is drawing so much current? Anyone seen this?

 

The only part of the ac that uses power is the blower fan....
So I'm guessing the idle might be dropping a bit when the a/c clutch engages.... Resulting in a voltage drop....so the regulator might be iffy...but have seen a couple cars do this with very high mile alternators.....(200,000 mile OEM ones...)...that still were working...
Just a heads up...one of the guys (at greasys) mentioned to me that the car-quest alternators seem to be lasting only about 2 years....so still not a good OEM equvelent...good for some...due to the $$ savings, but I can tell you the OEM denso's on other cars can go 200,000+ ....had had 3 do this...2 honda's and a Toyota Highlander currently (at 210,000+).
I have found denso made rebuilds from denso online for a decent $$....heck bet they are the OEM rebuilds they are selling....still 2x the cost of the rockauto ones.....

 

One extra thought....
About the blower...
Worn DC motors sometimes need a bigger surge current to get them moving....I would expect the fuse to blow if too far gone....check the grounds? Have also heard of a car or two that had corrosion issues on the back of the fuse block....

 

Did you try replacing the battery?

 

Hmm.... Blower motor should show a drop with or without AC on right? Also, the battery is fairly new (less than a year).

Interesting on the TYC as I have used them in the past and they lasted a lot longer than that. I guess I will find out.