2005 GT: Battery light and P0622 Code - Ford Mustang Forum
 
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post #1 of 3 (permalink) Old 05-20-2010 Thread Starter
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2005 GT: Battery light and P0622 Code

After five years, I finally had to replace the battery in the Mustang. On the first run out, I had the red battery light up on the dash. We had somewhere to go, or else I would have turned right around and come home!

The battery light persisted through a two other starts, and on the way home, the headlights started getting dim, the ABS and traction control light came on, and finally the headlights just died. Driving that last mile on a dark, windy country road was just awesome!

I ended up stalling it right outside the garage door, since my wife couldn't get it open in time, and it wouldn't start. I pulled the codes, and got a P0622 (Generator Field "F" Control Circuit Malfunction) which seems to indicate a bad alternator. I waited a few minutes, tried again, and the car started.

I'm going to check the voltages when I get a chance this weekend.

So, what I'm wondering is:
  • Is my best course of action is to pull the alternator and battery, and get them tested?
  • If I didn't see the battery light before the dead battery, does the new battery have anything to do with the issue? Is it possible for a bad battery to kill an alternator?
  • Any thoughts on what caused this to happen all of a sudden?
Thanks!

--Tim


2005 Mustang GT in Torch Red
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post #2 of 3 (permalink) Old 05-21-2010
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A new battery should not have caused the altenator to fail.
There have been more than a few of the alternators going bad on these cars latley.






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post #3 of 3 (permalink) Old 05-26-2010 Thread Starter
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Last night I checked the battery voltage (12.5 volts, a.k.a. dead) with the engine off, and managed to crank it and the voltage didn't change. So I'm really sure it's the alternator. I pulled the alternator and took it to the auto parts store, and they put it on their testing 'lathe', and they didn't see any issues. I couldn't think how a bad battery would behave like that, so I did end up getting a remanufactured one from Ford ($320 later... Ouch!) and I'll put that in tonight or this weekend.

The guy at the parts store said that it might have been that the brushes weren't contacting correctly, and my bumping it around removing it and bringing it in could have re-aligned them, or it was the voltage regulator, which apparently they aren't checking for.

2005 Mustang GT in Torch Red
C&L Cold Air Intake/Diablosport Predator Tune
Tokico D-Spec Shocks & Struts
Steeda Sport Springs/Front and Rear Swaybar/Front Swaybar Brace/LCAs/Adjustable Panhard Bar and Brace
Steeda-branded Borla Stingers
Steeda Underdrive Pullies
1965 "GT" Logo and some other chrome bits
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