[Bingo6104]

OK here is the deal I have had alt and battery replaced about 3 years ago. A few days ago I noticed the battery and brake light coming on at low idle. It would go away at 2000 rpms. I had it tested at advance auto and they said the alt was bad.
Well today I was driving and the check engine light came on them my speedo and tach gauges went dead. The rpm would jump up and down some but was mostly dead.
Then the power of the motor went down. I couldn't pass a scooter and it was making some chugging sounds.
I made it to O'Riley's and they had a hard time getting a ECU read out. When they finally did it popped a code of p1507 . They put a charge on my battery cause what ever is happening killed it. They took their machine and tested my batt and alt and it said it was fine. After the car gets a charge it will run fine for a few then it just dies .
Would the alt cause all of this ? Any suggestions? Stuff to try ?

 

[canubaru]

bad alt.

 

[Bingo6104]

bad alt.

If it was going in and out is that why it would it would read good st one place and bad at another? O'riley's has a lifetime warranty on one for 128 then you have your core exchange . Would a fautly charged system make it throw codes like that p1507
Is the alt another part is better to be replaced by a OEM part from the dealer ?

 

[cardoc]

Battery condition effects the alternator output. If the battery is weak it will cause what you describe. The problem you posted didn't drain the battery, the drained battery caused the problems.

Also, check the ground connections for tightness and corrosion free. It is best to replace the alternator and battery together. When a Subaru alternator fails, it is generally because of a weak battery and the alternator is overworking to provide the needed amperage to run the car. Especially in automatics.

 

[Bingo6104]

Thanks for the info the battery is under warranty . The alt isn't though. Even if the battery past the test could it still be bad ?

 

[cardoc]

Depends on how they tested it. If they tested amperage output with the engine off, it needs to be above 450, or no more than 150 amps under what the CCA shows for the battery. Also, conductance between the battery and block need to be checked. This will let you know if you have a weak ground. A loss of more than 50A indicates a loose or corroded ground. Same with a test between the battery and body/firewall.