2nd Gen Non-Engine/Transmission Batteries?? Altenator??

[PMarsteiner]

So I go to the airport today, and come back home about a 40 mile round trip. The trans starts going in and out of lockup just a couple times @ 40mph. I'm like here we go again. So when I get home I pop the hood and notice that the batteries are wet. I haven't washed the truck nor has it rained in some time so after inspecting the batteries it looks like they are boiling over out of the vent caps at the top of the battery. So I go back to NAPA to ask if this is suppose to happen. ( Exide Batteries by the way) They don't know. They think the alternator is over charging the batteries and I need a new alternator. So The only way to check the alternator by them is to take it off the truck. I haven't done that since I believe if the alternator is charging the batteries then it is good. Voltage regulator? Any help would be appreciated.

 

[kenny61]

just check the voltage with a meter you should have around 14. 7 volts with the truck running anything much higher and you are overcharging. you might want to let it run a few minutes to let it settle down if the heaters arecycling

 

[DPapworth]

Voltage regulation is controlled by the PCM. It is pretty much impossible for a "bad alternator" to overcharge batteries -- the alternator only does what it is told, or it does less (when it is broken).

First thing to check is all of your high current cabling. Battery connectors, grounds, alternator connections. Are they all clean and tight?

Next, pull codes from the PCM and see if it is complaining about anything in the alternator circuitry.

Measure voltage with a voltmeter at the battery, and also at the PCM. If the PCM thinks the system voltage is lower than it actually is (due to a bad connection somewhere), then it will overcharge the batteries.

You can also try running with just one battery while you diagnose things, thus simplifying the system. The truck will start and run just fine on one battery -- you only need the second one in cold weather.