Last weekend I was out on a 150 mile Z club run in some hot weather. On the return trip home, I noticed my Charge warning light was on, and that my voltage was dropping... Clearly I was running on battery power alone, such that I couldn't even use my turn signals! I pulled over and discovered what you see in the pictures.

The alternator is from MSA and is only 2 years & 15k miles old. Though we were traveling at a fast pace, I wasn't doing an overt/unusual amount of boosting or high revving (I don't flog my car, but it is a sports car after all). There was a fair number of hills to climb, and I did use the AC on flats or downhills.

So, my question to all of you is: What the heck caused this??
What should I do to diagnose if it's the alternator at fault (or is damaged), or if it's something connected to that wire?
If I need to replace that white wire, where the heck does the other end go to?
And how can I tell if that little capacitor-looking thing connected by the small wire is damaged?

Thanks!

 

That's a new one on me. That capacitor really isn't needed, something to do with noise, I believe.

 

It looks like it arched. Are any of your fuses including fuseable links fried? it looks it it was arching around that wire a bit. or it managed to ground itself by shorting out a few or all of the diodes or the windings in it.

And the wire might need a new Eye ring on the end of it but it seems to have for the most part survived.

 

As far as I can tell, the fuses all look ok. In fact, I can still start and drive the car on battery power alone (I recharged it with an external charger). I did a quick test touching a voltmeter to that fried wire, and I am still getting 12V to it, which means that I've still got a complete circuit to the battery. So that should mean the wire's still ok, and that something's up with the alternator, right? If I gotta replace such a "new" alternator, I'm thinking if there's a more reliable one I can go with that's "plug n' play"..

 

It's a sickness called "Oldness" happens when something becomes Old. mine did the same, but it cooked all the way to the fuse box. what hell that was. I replaced with a 2 gauge battery-starter wire. huge wire. but bygod it works great. I have also placed a military grade circuit breaker inline. no more fuse. real nice when you have to work on it. flip a switch. no hot wire at the alt.

http://www.powerwerx.com/_images/pro...185-50_lrg.jpg

i got this in 60 amp. I forgot what brand mine is, it's not Buss. But it is also High-Temp and you can mount on block next to Alt if you want.

 

Ok, did some more testing. I disconnected that wire from the alternator and started the car (on battery power alone). While idling, that wire is still reading 12V, since it's apparently still got a complete circuit to the now-recharged battery. However, the alternator was reading 17.2V So is that too much voltage beyond the operating range, or is that normal for an alternator to put out that much voltage (perhaps being disconnected tricked it into thinking it was trying to quickly charge a low battery?)?

 

Yeah, you shouldn't do that to your alternator. It'll fry the windings. Basically, you put your alternator into "Open Loop" with no battery to "regulate" it will spin into high voltages.

Here's the inline high amp waterproof circuit breaker. These are very common in marine applications:

http://www.westmarine.com/webapp/wcs...4&ci_sku=17549

Cheers,
LWW

 

These circuit breakers are great and all...but that doesn't resolve the question of what caused it in the first place, to avoid a repeat in the future. Because I'm still getting readings through that white wire, so it's still connected to the battery (or wherever it goes). Does that white wire go directly to the fusible links box, or does it go somewhere else first?

Wade, how can I tell if the alternator windings are fried from spinning "without a load" during the time I was driving it on battery power only?

 

Steven, That is the main "charging" wire to your battery, that's why you still get a 12v reading from it.

You'd have to crack the case on the alternator to see if any of the diodes are blown.

It's easier to take it to Kragen or AutoZone and have them do a load test on it to see if it's still operating within normal parameters.

I suspect the internal voltage regulator on that alternator is toast anyway, which is probably what fried your battery wire in the first place.

WW

 

I kinda had a feeling it might be the voltage regulator.. Do you reckon I should still stick with an OEM replacement alternator, or should I go with something else that'd be a direct drop-in?