2004 accord coup 2.4L.
Battery warning light came on 2 days ago. Then abs, air bag, break light all came on today and battery dead.
Battery voltage 11.8v when car is off, 8.8v when jump started.
Closer inspection in engine bay, I see the alternator is not spinning (seized) but serpentine belt is running and tension is ok (check the arrow and its in range)
This car just had it's starter replaced 2 weeks ago. The battery is 2 years old 51R.
Is there any diagnose I should do before just replace the alternator? Any suggestion is appreciated. Also, how much would it be to pay a mechanic to replace this alternator (labor and part). Thanks.

 

Just removed the alternator and it spins freely and smooth.

 

Are you sure it was not spinning before? You may want to spin the other pulleys with the belt removed like the tensioner, PS pump, etc to see if another pulley is causing an issue.

Some shops may be able to bench test your alternator to see if it is working properly. If you go with a replacement, I'd recommend a Densoaftermarket brand or find a place that rebuilds alternators. In my opinion, the rebuilt alternators from the parts stores are iffy at best.

 

You are right. It was spinning freely. I have put the alternator back and jumped the car. The battery voltage is 12.05v before jump start and 9.5v after start, 9.0v after 2 min of running. I think my best bet is to replace the alternator.

 

I'm in US but can only find denso reman alternator. Other option is Remy new alternator for only $130 on amazon or Carquest reman/new alternator for $150/$220

 

The Denso reman is the option I'd go with.