Alternator on it's way out? or marginally bad?

[mike-tracy]

I have a frustration with this car, in that idling when the engine is warm, my gauge says I'm sitting pretty at 14-15 inhg. When I turn off the headlights, it goes to 17-19 inhg.

When I turn off the headlights and defrost (no ac compressor installed but fans run), I get 20-21 inhg!

Tested voltages at battery today. Idle stays right around the line between 0 and 1k rpm always, but idles like butter at 20-21 inhg on the gauge with everything off.

13.84v - lights and defrost on
13.96v - lights off and defrost on
14.1v - lights and defrost off.
The voltage (and idle) stays rock solid.


During the winter I always run defrost and headlights, and let the car warm up for a minute or two before setting off, so the crappy idle bugs me.

[alexandermf]

Sounds like its on its way out

[Apex3]

Yup sounds like it to me. Mine was doing that too, more severe by the time I noticed, eventually it just started dying after I drove it for more than 20 minutes or so when I'd come to a stop, new alternator fixed it.

EDIT: Actually that's kind of weird that the voltage stays constant. But alternators do weird shit sometimes so it still gets my vote, take it to Autozone and have them check it.