I'm really hoping this is my alternator. The passenger side battery yesterday was hissing , hot , and putting acid out the top of it. It started when I noticed the dash gauge reading 11-12volts. I took it to Advanced auto parts for their scanner, and they said the alternator was putting out 19volts. and that the passenger side battery was bad (I figured that lol) I figured that if the alternator was putting out high voltage wouldn't the gauge read on the higher end? Does the alternator have an internal regulator? Why would only one of the batteries be boiling and not the other if the alternator is putting out too much? Any other ideas what it might be? I put a new battery on it (problem still there) and a new alternator goes on today. I'll keep everyone updated.

 

Check all battery cables and terminal connections. If one battery terminal is loose or has high resistance it can cause the other battery to overcharge. The alternator is controlled by the ECM.

MikeyB

 

That dash gauge ain't worth a dang, it's just a dummy gauge. It's controlled by the ECM...

Check your ground connections to the block, follow the battery wires, make sure there is no corrosion and that they are not stiff and brittle.

It does just sound like a bad alternator, but the batteries could have had something to do with it, the average lifespan for these batteries is about 4-5 years. Get the other battery tested while you are at it... most folks recommend replacing the batteries at the same time.

I would say it's just that one battery because it was the weak one of the two.

Make sure you test the alternator before you buy a new one.

 

After putting in the new battery the alternator was still showing an output of 19volts and almost immediately started frying the new battery while going through the tests. It was the older of the two batteries, although I'm not sure by how much since I have only owned the truck for 2 months. The funny thing is, I put new gauges in the night before this happened, so i thought that I might have a ground somewhere, but I can't think of how that would be. Ignition wire is to cigar lighter, others are to the dimmer wire, grounds are to a steel plate near the emergency brake pedal.

I had this issue with my '89 Cummins, and the voltmeter read high voltage when the regulator was frying the battery. Why wouldn't the voltmeter be reading high if the alternator was frying the battery? Basically I guess I am unsure what the voltmeter on the dash is telling me...

 

I am not sure, but I think that the voltmeter says what the ECM thinks the output is, not what it actually is.

Case in point, I have a grid heater delete, but when it's cold enough for the grid heater to activate, the volt meter still shows a drop, even though there is not any cables or grid heater to draw the current.

 

Huh...that is interesting. I guess I am going to put in the new alternator and see what happens, hopefully that fixes it.

 

Keep us posted.

 

I installed the new alternator and it is still reading 18.8-19.0 volts for a charge. After about 20 seconds it actually blew one of the caps off of the new battery. I'm guessing it wasn't the alternator. All connections are tight, what else is there?!?

 

Check all the connections, including the starter. Something is telling the alternator to put out that much voltage.

Why would you buy a new alternator without testing the old one first?

Guardrail

 

The ECM tells the alternator how much voltage to put out. Remove the neg terminal conections from the batteries and then clean the ECM connectors. Reconnect the batterys and check the output again. If over 15.3vdc then clean your battery connections, alternator connections. and all ground wires from the batteries / engine to the body / frame. Good luck.

 

I'm betting the wire from the alternator to the passenger battery is corroded. I put a piece of 4ga on mine when it did this, I think OE is 6ga.

 

The root cause of your problem is a poor connection between the two batteries. remove and clean the battery cable ends and the battery terminals of the cable that connect to both positive side battery terminals.

 

There is a temperature sensor under the driver's side battery. The ecm uses a temp reading from the battery on the driver's side, to determine it's rate of charge. If the sensor is reading too cold, the ecm will jack the alternator's output, to try and raise the charing rate of the driver's side battery.

Being that the alternator is hard wired to the passenger side battery, it takes the brunt of the hit. The alternator is simply doing what it is told to do, which is overcharging the passenger side battery and causing it to boil off.

Check under the other battery, and look for a disc shaped sensor, that has to contact the bottom of the battery case, and the wiring for that sensor needs to be in good shape.

Also clean up your terminal connections while you have things apart.

Good luck

 

I hate to say it but I think I am taking it to the shop to diagnose this one. This truck has been nothing but problems since I have owned it (2 months) and I have put roughly $5500 dollars to it so far. To say that I have lost enthusiasm to work on it right now is an understatement. I had less go wrong with my 12V and 24V combined over the course of 5 years than I have with this CR. I will keep you posted as to the final outcome. Thanks everyone for your input and have a Merry Christmas!!

 

I relocated both battery,s to the rear, The wire coming
from ecm, went to finder ground. I had no disc.