OT? - Bad alternator?

First: Check ALL ground connections by removing sanding and reattaching. Check Battery connections, ground connections to engine,body and starter connections as this is a common tie point. Yes a shorted diode in the alternator will drain a battery but, you clamed 14 volts charging at some point so I think that eliminates that part of the alternator. Post back on this post on what you find. eddie

Hi,

My understanding, backed up by the literature that comes in the box with a new alternator, is that it can be a chicken or egg situation: battery may not have been properly charged by a failing alternator and died, alternator could have died due to bad battery causing it to overheat a diode, etc.

Warning I've read several times is when replacing alternator to have the battery checked. A six year old battery is definitely getting toward the end of its life anyway, so the fact you swapped out both should keep you in good shape. Follow Eddie's advice on cleaning everything, and let us know how it goes!

Another tip I've read on new batteries is to make sure they're first well charged up from an external source to avoid excess strain on the alternator. If you've got a trickle charger, you could stick it on overnight to do this. I really don't know if that helps, but I've tried it a time or to and it did no harm.

Rick

Sounds like you had a short circuit diode in the alternator - allows the battery to discharge back through the alternator windings.

Dave

As Rick suggested: I ALWAYS charge a new battery to a full charge ASAP using a 10 amp taper charger. Stores give you a battery about 1/2 charged usually and then you run the heck out of your alternator to charge it.

Hi Guys;

Gonna be lazy and have it chauffeured to the happy dumping ground via the city sanitation department. When they run 20 bucks rebuilt on

ain't gonna lose any sleep over what happened. Just trying to figure out why the tach and voltmeter went nuts after putting the new battery in. Thought I detected a whiff of ozone, but they were pumping a lift station not too far away also. :) I had cleaned the terminal connectors, and all cable attachments are clean and tight. The alternator had a "moment" about 3 weeks ago, where the needle jumped a bit indicating a charging state a bit higher than it had ever been before accompanied by a grinding and funny smell, that's why I wasn't too surprised when I had to replace both. I've never seen a concurrent failure, so like you say, which came first the chicken or the egg, most likely never know, but figured someone that reads the NG that has a better understanding than I might be able to guess what may have happened.

Thanks again. Mark

If the alternator failed from a shorted diode, it most certainly could run down the battery. There are other ways the alternator could fail though.