Alternator Difficulties

[Brian_911]

I replaced my alternator in November of last year with a Bosch OEM alternator. I just had the engine rebuilt, and following the rebuild my alternator is bad again. I just pulled the alternator and my local auto store can't test it. Before I spend a couple hundred dollars for a new alternator, is there anything associated with pulling and replacing the engine that could be causing the problem?

Full symptoms: Four days after I picked the car up (driving each day), the engine would not start - dead battery. I charged the battery, took it to my parts store and got a satisfactory load test on the battery. I put the battery back in and drove the car, noted that battery voltage was poorly regulated for a while (12 - 17.5 VDC) and now the alternator is generating no voltage - system voltage simply remains battery voltage. If I load down the electrical system (with headlights, wipers, etc) voltage drops in keeping with a battery load curve. Revving the engine has no affect at no load or at heavy load

Connection on the back of the alternator were correct. Belt tension on the alternator was fine. I have the 8 month old alternator out now. Any ideas of anything more I should try before I just give in and buy a replacement alternator?

Thanks for your help!

[Brian_911]

No new lessons learned here. Replaced the alternator and now I'm getting a solid 13.5-13.7 VDC when the engine is running.

[47silver]

i had 2 bad rebuilts.
i also took my original alternator to get rebuilt.
The original has pressed in diodes whereas the rebuilts have loose diodes. The alternator repairmen told me that these are less heat tolerant than the pressed diodes, so you get a shorter life.
he recommends the pressed in diodes so i am having him rebuild the original alternator for me. it is expensive??? 400 bucks as the stator needs rewound also.