Subaru alternator question...

Hey guys, I've hit an issue with my 2002 Subaru Outback 3.0, 90k miles, auto. This week late Thurs night, and while driving to work on Friday, the "brake" light and the "battery" light, slowly began to flicker, and then stayed lit on the dash. After doing some searching it was suggested I had a bad alternator. So I got a new/rebuilt alternator swapped it out, and I'm still having issues.

I tested at the battery using a voltmeter. On Friday when the lights were on I had:

Car off 12.56

Car on 12.31

Car on with a/c on 12.16

This evening after replacing the alternator on the first crank I had:

Car off 12.51

Car on 14.38

Per the instructions after letting the car run for 15 minutes I had

Car running I had 11.81

Car running with a/c on 11.62

After running a total of 20 mins, and then turning the car off I had 12.40 and its going up. And the weird thing is that I have no lights on the dash even though the numbers are much lower.

Should the now lower numbers be a concern? Is my new/rebuilt alternator broke? Is there something else going on?

I'm kind of at a loss as to what I should be checking now.

FYI, I bought a bad new alternator once. From what I understand, it's not all that uncommon.

Either you got a new alternator that only worked for a short while, or you have a bad connection in the power supply or ground circuit that heats up and increases resistance. Check the voltage from the alternator output wire to the case and see what you have compared to the battery.

Ok guys here's some more info.

I tested the battery again with the car off 12.4. I checked at the power supply going into the alternator and got 12.4. I then started the car. Upon initial start up I had 14.2, but as I left the voltmeter on the positive and negative points of the battery, it began to go down. I took the car for a drive. Here's where things got interesting. After driving for about 15 mins making loops close to my house, I had the a/c on and it started not blowing cold. Shortly after, like less than a minute the ABS light came on. I was less than 5 miles from my house and headed directly home. While coming home, the speedometer and tachometer shut off. And then started getting all wonky, they would come on, flicker a couple times, needles jumping all over, and then shut back off. And kept doing it until I got home. When I got home, without shutting the car off I tested again 8.51 at the battery.

I've called and got another alternator on order and it will hopefully be here tomorrow. Is a bad alternator the correct diagnosis? Anything else I should check?

Also in the 21 minutes it took for me to type this up, I tested again and at the battery it is 12.08 and at the alternator it is 12.08.

Unless there is some sort of monstrous electrical draw, I'd say alternator...unless the belt is slipping, or the crank pulley is turning on the crankshaft. The voltage has come back up because the load is gone, Betcha it won't have enough amperage to start the engine.

Ah, rebuilt alternators from Adzone, noted for not being very reliable. Check your battery terminals for corrosion and loosness.

My thought was a draw. Check it out.

And, it almost goes without saying, but check the battery cables and clean all the grounds.

Alternators on Subies seem to have a pretty high failure compared to others. My wrx went through two. One rs went through two, race car has needed one. Legacy needed one when I bought it.

iceracer said: Ah, rebuilt alternators from Adzone, noted for not being very reliable.

Add O'Reilly's to the list, as that is where this one came from.

lol the autozone alternator on the geo prizm (toyota rolla) needed replaced every 6-12 months... thankfully it took more time to get tools out and do it then the actual swap...

Streetwiseguy said: Check the voltage from the alternator output wire to the case and see what you have compared to the battery.

So you are saying with the car running test from the power lead going into the alternator to the alternator case?

I just got back from having the new/used alternator tested at Oreilly and it passed.

I'm kind of at a loss as to what is going on. I've cleaned the cables to the battery but will check those again. I'll also be checking the grounds to make sure all is good. I checked my fuses with a test light but will be rechecking those as well.

What else am I missing?

Parts store alternators and starters are not to leave the building without going on the tester first.

Belt is tight? Tensioner is free? Grooves in belt are not shiny and thin?

It took I think 4 replacements on my dads legacy (every few months) to finally get a good rebuilt one from kragens. Have you checked the dealer? They are $$$, but if you dont want to have to carry a spare it might be worth it. At least you can swap them in less than 10 minutes with a bit of practice.

When it comes to starters and alternators, I prefer used OEM ones from the junkyard (rather than cheap/reman units from the part store) whenever possible. The rebuilt ones are particularly horrible when it comes to infant/instant failures.

Bryce

So I checked all the grounds, I checked all the fuses I could in the engine compartment and I got the new/used alternator in, again. When tested with car off battery had 12.11. Car on the battery tested at 14.35. Not 5 minutes in to letting it run the numbers started to go down, and then smoke started coming from the alternator. Immeadiate shutdown and test. 11.51 at battery and at alternator. Cranked again, no more smoke, but the numbers kept going down. Turned off and pulled the alternator again

Is it possible that the alternator could test right at startup and then overheat and not charge the battery correctly?

I'm planning to take the alternator back and try my hand at another new one. Should I take my battery in and get it tested as well?

And 8 mins. That's how long it took me to get the alternator out this time.

Just to keep a running update.

Battery tested fine. Picked up another new/used alternator and will give it a go tonight. Tested it before I left the store and it tested fine.

And Streetwiseguy, belt is new, less than 3 months old, still looks brand new. And I made sure it was in all the right grooves.

When I was working in the repair/srvice business, i reconditioned alternators. Never had a come back. The usual failure is from worn brushes or the voltage regulator failure.
So I wonder just what is done to these "rebuilt" units to cause the high failure rate that is so well known. Warranties are fine but they don't compensate for the time you spend doing the replacement.

Is there a shop in your area that specializes in electric motors, startes and generators ? Might be worth a try.

iceracer said: Is there a shop in your area that specializes in electric motors, startes and generators ? Might be worth a try.

Not sure but I will look. We haven't been here that long so I don't know where all the shops are yet.

You're right though that might be worth looking into.

octavious wrote: When tested with car off battery had 12.11. Car on the battery tested at 14.35. Not 5 minutes in to letting it run the numbers started to go down, and then smoke started coming from the alternator. Is it possible that the alternator could test right at startup and then overheat and not charge the battery correctly?

That's what it seems like.

Ok so here goes. I took the alt back and swapped it for a different one. Took the battery in and tested it as well. And it came back fine.

New alt, same batt, 12.45 with car off. 12.45 at alternator wire and battery negative. 12.45 alt case and alt wire. 12.45 alt case and positive wire at battery. 14.28 initial car startup and running. But then it began to go down. When it got down to 14.08 I shut it off.

So, I took the Optima red top out of the 911 and put it in the Outback. It read 11.99 car off. 11.99 at alt wire and battery negative. 11.99 alt case and positive wire. 14.24 car on and running. 14.24 negative battery and alt wire. 14.26 alt wire and alt case. After a few minutes it was at 14.18 and going down when tested at the battery. A few more minutes and it was down to 14.02 and still going down I shut the car off.

So to me its not the battery because it exhibits the same downward trend with both batteries. But what do I know at this point.

But just to make sure, I put the old battery back in the Subaru 12.7 car off. 13.81 w car running and going down. 13.52 with a/c on and still going down. It got all the way down to 13.05 and I stopped messing with it.

As it was idling but working its way down to I checked all the fuses again, all were good, I even checked the ones inside under the dash. After I cut it off I checked continuity at the relays inside the fuse box in the engine compartment and all seemed good.

Color me confused. I have no idea.

How did this work out for you? I'm having similar symptoms in my 01 Legacy sedan: ABS light off and on, battery indicator, CEL (P1137 oxygen sensor?) and airbag light off and on.

(Sorry for bumping such an old thread - google brought me here!)

I've learned to keep spare used OEM Subie alternators on hand. $20 at the salvage yard and they are super easy to change. In fact, I keep one wrapped in a t-shirt and sitting in the spare tire wheel well.

The parts store rebuilds are too unreliable for me.

They are pretty easy to rebuild and the bearings and brushes are usually the problem.

If all you need is the bearings and brushes they are pretty cheap. Brushes are under $5 if they will sell them separately and about $30 for the OEM brush and holder assembly. The bearings are around $30 for OEM and $12 each for OES. If its the rectifier, diode, rotor, or any of the other main parts you might as well get a rebuild just due to the cost of the parts.

I have had nothing but problems with parts store rebuilds. I only buy either new for about $300 (eek!) or a rebuild for about $120 from an electrical shop. I have been happy with Maniac Electrical in Dallas.