I know this has to be bad.....

Black Sun 5.0 said:

Brand new battery, engine, the whole biz. Well I noticed my electric fan and DC Control unit, which was working fine, started to act flaky. I open the hood and noticed a white substance on the terminals of the battery. Obviously there is a problem. What would cause this?

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pasty or poweder-like?

Its battery acid corrosion - a simple mild alkali will clean it off like baking soda or a coke for that matter. You can apply petroleum jelly after cleaning the posts to prevent it from recurring.

and use some steal wool or sand paper on the posts too.

If you're all of the sudden getting a lot of paste on the battery, then it's boiling off one or more of the cells. Either the battery is bad or the alternator is overcharging. Some of the cheap batteries are bad out of the box or last only a couple of mos.

I'd pull it and get it checked. If the resistance gets high enough on the terminals or a cell opens, the alternator can output large spikes in voltage, particularly when a heavy load is removed from the system. It's pretty hard on the controller since it will attempt to provide the filtering that the battery normally provides. You could also get real unlucky and have the alternator take out the injector drvers, since they're not protected.

You definitely don't want to disconnect the battery in order to see if the alternator is charging, it's a bad idea.

I find it real odd. Did they check the battery. If it has a bad cell, it will continously boil off the sulfuric acid from that cell. Were any of them low?

As far as the alternator overcharging, one reason would be a bad diode bridge. If the bridge is bad, it will actually undercharge slightly at idle, but what happens is that as the armature passes the set of windings that's connected to the bad set of diodes, the regulator will turn full on in an attempt to generate more voltage. When the next set of windings hit, the field is saturated, so you end up with a voltage spike.

A bad regulator would also cause the problem, but it would most likely be shorted and the voltage would be high enough that you would have probably noticed it.

The regulator is easy to check, 14.4 - 14.6 V @ 2000 rpm, the diode bridge can be checked by measuring the AC voltage at the alternator. I'm not positive on the spec, but I would think that it should be less than .2V.

Another possibility is that the battery is draining overnight. If that's the case, the alternator will charge the battery at a high rate and boil off some of the acid. The battery should be at about 12.6 after sitting overnight.