Psychotic Alternator

[HighRev85]

This story starts off like any other. I'm driving around and want to open up my secondaries. So at a certain set of lights, I do just that. I get to about 3,800 RPM's and my battery voltage spikes up past 16V by my gauge, complete with a resetting EATC and flashing idiot lights. I bring it back down to 1,800 and now have a non-functional alternator. So I run some tests before I get back and I've discovered this:

The alternator will function and immediately overcharge (IE past 16V on the gauge) at any engine speed above 3,200 and can maintain a charge of about 14.5V if you bring it down to 2,500 or so. The EATC, ABS braking system, and Air bag system will reset itself when the system overcharges initially.

I replaced the voltage regulator (thinking it could be the problem) to no avail. I cleaned the battery terminals, checked, cleaned, and tightened the +B post on the alternator, and tightened the fan belt. I'm thinking it might be a bad ground or a short...but I have no idea where to look. Any help in the matter would be GREATLY appreciated. Thanks!

 

[SHOZ123]

Sounds like something is moving when at high rpms. Time for a rebuild?

http://www.transpo-usa.com/distr_us.html

 

[ohfosho]

its still a alternator voltage regulator problem...its obviously not 'regulating the voltage'???? try a different brand/store...

 

[HighRev85]

Yep, it was the alternator. One of the posts that go from the E-Field to the middle bearing (where the brushes make contact) had broken the sauder and would only make contact (or arc) at higher rpms. I fixed that and replaced the battery cables too. You think I'd be out of the clear...but now the car has trouble starting (or having trouble drawing current to start), no lights or anything when the key is moved to the "start" position. I suspect that it's one of the battery cables, I was a little overzealous and cracked the clamp that goes over the negative battery post...

But it all works! Thanks for the replies guys and gals

 

[40BelowSummer]

Usually when there appears to be power then when you turn the key it draws all the power it is a connection. Checked the Battery ground, starter/fusebox connections.

 

[HighRev85]

Usually when there appears to be power then when you turn the key it draws all the power it is a connection. Checked the Battery ground, starter/fusebox connections.

That was it. I kept the hood up after checking the battery connections at the starter and noticed smoke curling from the positive battery post...evidently the round end of the battery cable (the name escapes me...wow I feel dumb) broke. The air gap was causing resistance, which made the current arc over the air gap. I retightened it for a temporary fix, but plan on returning that piece of crap cable/wire/whatever you want to call it.

Thanks for all the help guys and gals