My 2005 Impreza Outback Sport isn't charging the battery and everything points to the alternator, except that the charge indicator light (battery icon) doesn't light up. Ever. If I charge the battery the car will start and run, until the battery dies but the light never comes on, whether the ignition switch is "on" but the car isn't running, or it is running. Of course I can't remember if the light used to come on at start up or not. I assume it did. My understanding is that the indicator light circuit also supplies voltage to the alternator to provide the initial current to get it going. So is it possible that the problem is not the alternator but the indicator light circuit? Is there a way to test that? The battery voltage is right on 12 whether the car is running or not, and I've cleaned and tightened the battery cables.

Thanks!

Will

replace the Charge fuse.  That could be all that's wrong.   BUT.........if it keeps popping the fuse, or.........

If then light still does not come on with key on, try providing ground the the BW wire at the ALT plug with Key on.  That should light the indicator.

 If it doesn't, pull indicator bulb and verify if burnt out or not.

If it does light the bulb when manually grounded, but not with ALT hooked up at key on, then Alt is shot.

Your understanding of the battery indicator light is correct. Current has to pass through it to provide power to the exciter inside the alternator. The battery light should turn ON when the ignition is turned to ON, like the rest of the warning lights do. If that doesn't happen then follow the good advice given by FerGloyale by grounding the B/W wire going to the alternator. If the light still doesn't work then either the light is bad, power from the ignition isn't getting to the light, a blocking diode inside the cluster is bad, or there is a wiring problem on that circuit.

The alternator provides a path to ground normally until it generates the field. Then there is a charge on the windings and the current stops flowing to ground and the light goes out, unless there is a problem with the alternator.

Thank you FerGloyale and Cougar! I had checked the charge fuse and it looked ok, so I'll move onto grounding the B/W wire and let you know the results.

Thanks again,

Gardener

You're welcome for the help. Let us know what you find out with the test.

I finally had a chance to do the test today, and when I ground the B/W wire and turn the key to ON, the battery light comes on! When I reconnect the wire to the alternator it does not come on. I assume that means that the alternator is defective in a way that prevents the current from reaching ground? Thanks again, I'll feel better about replacing the alternator now.

Gardener

16 hours ago, Gardener said:

I finally had a chance to do the test today, and when I ground the B/W wire and turn the key to ON, the battery light comes on! When I reconnect the wire to the alternator it does not come on. I assume that means that the alternator is defective in a way that prevents the current from reaching ground? Thanks again, I'll feel better about replacing the alternator now.

Gardener

yes that's definitive fault in the Alternator