Hey Soobs,

 

A while back the alternator charging light (battery and hand brake) lit up on my 1993 Legacy LS. I attributed it to something weird going on in Kansas. Anyway, I ended up replacing the battery and the alternator and everything seemed O.K. A few months later during vacation travels, the light came back on so I attributed it to a faulty rebuild. I got a free replacement (when checked with a meter it wasn't putting out enough juice) and everything was fine again. Well, this evening towards the end of an 800-mile drive the light again started to come on. It only comes on while accelerating or driving over about 65 mph, or up hill - all seemingly load related. The peculiar thing is that just like the other two times, the problem showed up only after about 10 hours of pretty much nonstop driving. That, and that it just happened to occur in Kansas again! Could something other than battery/alternator be causing this? Car runs perfect otherwise.

how old is the belt?

 

is it tight?

The belt is maybe two years old at the most and it looks to be in good shape - clean, tight, no noticeable cracks. Maybe I should replace it just to be safe clean and quite tight. This morning the cold battery showed about 12.9 volts and when I started it the alternator was putting out about 14 volts, just like normal.

Seems like you are doing everything correctly to fix the problem. Has the car not started, or been difficult to start after a bout of battery light on the dash? If not, I am thinking you have some electrical gremlin creating a false warning light on the dash. Maybe a ground wire is loose or corroded? You may want to check the water level in the battery. I once bought a new battery, that I installed myself, only a short time later to learn that it was low on water. I never bothered to check the water level, thinking a new battery would be full of water.

Yep, water level is fine. I put a new belt on this morning and sure enough, the light starts to come on when the speed goes beyond about 65, or if I push it up hill. I don't think it's a problem with a faulty light as last time the alternator really was under-performing. My plan is to find a NAPA at the next big town along the way and see if they'll replace it yet again. I suppose it's possible that I got two bad rebuilds in a row. I'm hoping this doesn't become one of those chronic mystery things that keeps coming back to haunt me.

i had a pretty similar thing happen to me in an old f150 i use to have. after months of working on it; replacing the battery, alternator and selonoid , i finally figured it out. it was the starter. it was causing a short and didn't cause any noticable troubles until the truck was climbing , accelerating etc etc. it sounds a lot like your problem. hope this is of some help. curtis

Yep, water level is fine. I put a new belt on this morning and sure enough, the light starts to come on when the speed goes beyond about 65, or if I push it up hill. I don't think it's a problem with a faulty light as last time the alternator really was under-performing. My plan is to find a NAPA at the next big town along the way and see if they'll replace it yet again. I suppose it's possible that I got two bad rebuilds in a row. I'm hoping this doesn't become one of those chronic mystery things that keeps coming back to haunt me.

 

If there is some sort of extra battery drain, when the car is running, maybe you can detect it with motor not started, and with the ignition key turned to the "run" position. Put a meter on the battery, and see what amperage is draining from the battery. Your NAPA store counter guy can do this test.

 

Yea, it is possible to get two bad rebuilds. Stranger things have happened. If so, with your present alternator, I would think the voltage regulator could be the culprit.

I got 3 bad rebuilds from Autozone last year. Two were diode pack related and the third was a bad bearing. This all occurred within 1100 miles.

 

I would also have them load test the battery. It is possible that one of the internal plated could be shorted. I know you mentioned that it was a new battery but its worth a shot.

i was having the same thing happen a couple of weeks ago in my 91 legacy, my altenator was a rebuild, and was intermitentlly charging. i bought a brand new altenator instead of a rebuild for 40$ more and it hasn't done it sence. i also took it on a four hour drive through mountain roads last weekend with no problem. if your starter was sticking and shorting out you should hear a light buzz, but if it was it could be the problem also.

I have a similar problem with the battery and brake light coming on in my 99 legacy outback. It only happens when it has been sitting overnight and disappears when the car is warmed up. I recently had to replace the alternator and went with a rebuilt one. As I said the light goes off when the vehicle is warmed up. Any thoughts?