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Old 01-14-2010, 11:40 AM
chev chev is offline
Chev
 
Join Date: Jul 2000
Location: Florida
Posts: 12
faulty alternator kill battery?

Re: '78 300d, 150Kmi DD

I recently had to replace my alternator (again) after 2 years on the previous AZone reman. (I know, I know... Bosch OEM is the preferred replacement), but since I originally replaced the one that's been in there since I bought the car in 1991, with an AZ part, ten years ago and it's warrantied for life, I couldn't help myself! If only they were self-installing...
Anyway, I'm already on that bandwagon.

After the previous alt failed ( 2 years ago) and was replaced, I also replaced the battery about a year ago.

Now with this third alternator-which charged at around 13.7-14.1 volts- last month the car again failed to start. I tried to charge the battery with my 10 amp charger. After an overnight charge, there still wasn't enough current to start the vehicle. I also noticed at that point that there was no apparent hydrogen outgassing.
I took it back to Interstate Battery, and they kept it for the long Holiday weekend-providing me with a loaner. They called, and told me that the battery had taken a charge and was ok, and we swapped the loaner.
Last night, I again had a nearly dead battery.

My question is this: if, as I suspect, one or more of the diodes were bad on the old (previous) alternator, can the resulting un-rectified electricity damage an otherwise good battery? I think it may be discharging internally.

I charged it overnight and I'm now showing voltages around 13.5-14 volts while engine is running, and do not have a charge warning light on the dash as I did when the previous alternators failed.

I've also checked to see if there is any major current drain with the key off, and, other than during the (wonderful Chrysler) A/C servo parking itself, there does not seem to be any major current flow. There is a small current drain, but I think it's just the clock. I'll find the appropriate fuse and see if I can eliminate that as a possible cause, next.

As a side question, are OEM diode packs still available for these, and where? I kept my first defective (original??) alternator rather than turning it in for core, in case OEM parts were available, and I wasn't satisfied with the AZ rebuilds. I used to diagnose and repair my Dodge Ram van alternators years ago, and parts were readily available back then, and it was really easy.
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'63 Triumph Bonneville
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