97 Legacy GT Alternator Output

trolleyop

Last night the lights on my 97 Subaru Legacy GT were changing from dim when I was idling to normal when I accelerated. I could hear the speed of the heater fan varying, too.

I checked the alternator output at idle and found it to be at approx 14.25 volts. When I turned on the headlights and heater at the same time however, the voltage dropped to approx 13.8 volts and did not recover to 14.25 volts until I accelerated the engine.

By comparison, I tried the same test on my 2004 Subaru Forester and found that the voltage would briefly dip to about 13.9 volts, then recover to approx 14.25 volts while still idling.

Does this sound like the alternator/regulator in my Legacy is going bad? (Maybe the brushes are wearing down?).

The original alternator was replaced during a 2001 recall (The car had approx 47,000 miles on it then). The Legacy now has approx 120,000 miles on it.

Thanks. Any help will be appreciated

paisan

That sounds about right. I wouldn't let it go too long. It's an easy and relatively cheap fix, a DIY even for the greenest of folks.

-mike
Subaru Guru and Track Instructor

xwesx

Agreed. I let the alternator on my '96 go too long. It got to the point that if I had my lights on during idle, the battery would wear down and the car would stall out. It took me 20 minutes to replace it.