robm Posted March 29, 2017 Share Posted March 29, 2017 The charge and brake failure lights are glowing at idle. They go out if I rev to 3000 RPM or so, and maybe less if the car is warmed up. This is usually a symptom of the alternator failing. Just to make sure, I cleaned all the battery terminals and clamps, and the ground connections on the engine. Then I measured the output voltage. I am getting 14.62 V on the battery terminals, and the same between the battery + terminal and the engine block. There is no AC on the terminals, so I know the diodes are good. But the charge and brake lights are still glowing. How can this be, if I have full voltage on the terminals? Link to comment Share on other sites More sharing options...
DaveT Posted March 29, 2017 Share Posted March 29, 2017 Seems odd... I never bothered to measure the battery voltage when I got those symptoms, as I had already known from previous experience what it meant. It's always been one of the slip ring brushes in the alternator has worn to the point of barely making contact. Maybe it's making just enough to still output at raised rpm, but not at idle. Link to comment Share on other sites More sharing options...
DaveT Posted March 29, 2017 Share Posted March 29, 2017 Replacing the brush fixed it in my cases. Link to comment Share on other sites More sharing options...
MR_Loyale Posted March 31, 2017 Share Posted March 31, 2017 I always just replace the unit and it fixes issue. Link to comment Share on other sites More sharing options...
rapidfire10ring Posted April 3, 2017 Share Posted April 3, 2017 Early Subaru alternators are notorious for having the hi-speed diode fail. The alternators are not service friendly. I bought several at a wrecking yard and immediately tested them at an auto-parts store. They all read good UNTIL you used them and the alternators were all overcharging. Shucks-O'Riley sells a LIFETIME alternator replacement that I opted for and I have never looked back. A failed alternator can cook many electrical circuits, get rid of it fast. Link to comment Share on other sites More sharing options...
robm Posted April 4, 2017 Author Share Posted April 4, 2017 I didn't think of the regulator being bad. The 14.26 V @ idle is probably a giveaway. I will check the voltage at 2000+ RPM. Link to comment Share on other sites More sharing options...
robm Posted April 10, 2017 Author Share Posted April 10, 2017 I checked for overvoltage. 15 V at 3000+ RPM, so I have a bad regulator. It is not supercritical yet, and I am traveling overseas in about 2 weeks, so I will leave it alone for now. Only short trips around town, I shouldn't wind up with a boiled battery or burn-out bulbs. Maybe I will buy another off Rock Auto just before I leave, so I will have it ready to install when I get back. Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now