Yes, sounds like it is your alternator. Replace it before you get stranded. As stated, its an easy swap. Shouldnt take more than 30 minutes.

 

The OE alternator finally gave out last week after 8 years and 130,000. Rebuilt one went in yesterday at local repair garage and changed the serpentine belt at the same time.

 

You were right.. It was fairly simple to change. Sad the the OE alternator only lasted 87K mi.

 

I sold my 06 gt stang to a friend. Has 59k miles, c&l race intake, PA performance 200 amp alternator, brand new battery, charge motion delete plates, tune from BAMA and a few other things. For some reason the battery indicator on the dash keeps going up and down and will eventually the headlights will start flickering on and off along with the dash lights. The alternator and battery have been tested, alternator is at 14 amps and the battery is brand new. Checked all connections to make sure they are not loose or burnt in any way. The alternator cable was upgraded to the larger cable to handle the larger alternator as well. Made sure the correct tune is on the car as well. When this happened the next morning the car was completely dead. Had the battery recharged and would last about 50 miles before the battery indicator started to fluctuate again. I have no idea what is going on. Does anyone know or have any suggestions.

 

so his battery died again and autozone gave him a new battery and ran the test on the alternator again and this time it was only putting our 10.6 volts. He just got one from there and installed a cheap one smh. I am getting the 200amp paperformance alternator back. Any recommendations on what to replace on it to make it functional or new again. TIA

 

Count my 2007 V6 automatic coupe in this mix too - same thing you describe. Power windows, even the power steering (turn steering wheel while parked) causes RPM drop . Bone stock; looks like he original plug wires and alternator, AAA battery age unknown. No dash lights, no movement on the battery gauge (volts or amps ?!). AutoZone AND O'Reillys tested battery and alternator on the car and said they're OK - this wasn't a load test though.

I think i'm gonna try a new alternator - stock 135 amp, BUT i'm gonna have the new alternator bench tested before i put it in. Seen new alternators that don't perform up to spec.

Did you figure it out (i hope, i hope, i hope )

 

Unfortunately, I never did figure it out, but I did sell the car. Moved up to a 2011 5.0 and very happy for doing so. This problem with the idle reaction to the electrical strain was a pain in my ***. I put in additional grounding from block to body, cleaned connectors, etc. etc. Some people I talked to said something about one of those body ground/resistor kits and I was considering them when I found my current car. Sorry I don't have any insights, but please post if you find a solution. Still bugs me and I don't even have the car anymore! Good luck!