I've tried 3 different batteries and they all overcharge to the point that they make a bubbling sound and leak some around the cap.

At idle the system is at about 14.5 volts, which should be okay (the typical range for a car's electrical system is between 13.8 and 14.4 VDC). However, I haven't checked the voltage at higher RPMs; but even when just idling for just a few minutes it makes the battery bubble.

A new voltage regulator was installed along with a new alternator when I first got the truck.

Why would 14.5 volts overcharge the battery? Is there something I'm missing? I don't mind replacing the voltage regulator again; but is that the problem?

 

Fridays suck around here for some reason...nobody around. You might also try posting in the Electrical section and see if that gets you any answers. Not something I've run into (yet) so I don't know anything about it!

 

Im not an electrical man, but I recently had mine tested as well and i was told that the alternators on our trucks should be putting out about 13.4 volts. New alternator or not, it sounds like something is wrong with it. I would try swapping it out, if you got the warranty for another one first. 14.5volts is a lot and will definitely cause your batter to overcharge.

 

Overcharging the battery is probably the alternator, new or not.

 

Okay, as it turns out, 14.5 volts is slightly too high, as the "gassing voltage" is right at 14.4 volts (I've long known that 14.4 volts was the upper end of the acceptable range but I didn't know why, nor did I know that there was no leeway there). This is from Popular Mechanics, from an article about charging a car battery:

"The traditional charger is a simple transformer and diode affair that charges a battery to a constant voltage just below the gassing voltage of 14.4 volts."

So I guess the problem is with the voltage regulator, or perhaps its wiring. I wouldn't say it is the alternator, because what it is doing is normal. An alternator by itself will definitely overcharge a battery because there is nothing to keep it in check; the higher the RPMs, the higher the output; which is why there is a need for a voltage regulator to keep things at a steady voltage below 14.4. From Wikipedia:

"An unregulated alternator can put out a high level of charge, and can quickly ruin a battery."

 

When I had mine tested i was told my regulator was going out and not putting out enough.. send me yours, i'll send you mine, and we'll both be happy.

 

The new regulator seems to have fixed the problem so far. The one that was on there was fairly new, but generic and cheap. The new one was from an OEM in Japan, and was more substantial (weighed about twice as much). The old one had gotten worse than when I first posted this thread. The voltage was getting up to 17.5.

The new regulator keeps it at a steady 12.35 VDC, which is lower than what I'd like (I'd prefer it to be in the 13 VDC range), but I guess as long as it keeps it above 12 VDC then it is okay.

This also seems to have fixed my problem with turning the truck off. When I first posted this thread and the voltage was around 14.5, the truck would usually shut off with the key, but not always (not "dieseling"; just continuing to run normally, as though you hadn't touched the key at all). Then as the voltage started getting higher (i.e., as the regulator was getting worse), it would never shut off with the key. Last night after installing the new regulator, it shut off with the key for the first time in a while.

Edit: This is the new regulator. As I said above, it is working fine, but does anyone know what the blue wire is for? The old el cheapo regulator didn't have an extra wire outside the main green connector like that.