Well long story, my truck ( 06 2500 ) was way overcharging so I take it to the dealer. They say $2100 needs a emc. They would have to order it so I went and picked up my truck. Charging perfect. So I drive it for two weeks and everything is great. Well today I cranked it in a parking lot and noticed the amp gauge wasn't right. Right hand battery boiling just like before. Drove it home and unhooked the batteries and then hooked them back up. Now it charges like new. Two questions, what am I resetting and why does it only overcharge the right hand battery? I hate to spend $2100 if that's not the problem. Ok maybe I'm resetting the emc but it seems like I'm over looking something if it's only overcharging one battery. thanks

 

Most likely it is the crossover cable that is bad....it will not allow the ECM to see the drivers side battery state and it will cook the passenger side because it is overcharging trying to fix the drivers side.

They will look just fine but be corroded under the cover...you may be moving it enough when you remove the cable ends to allow it to work for awhile then it craps out on ya again. You need to put a VOM on that cable after you unhook it to see what it reads.

My 06 was doing the same thing last week and I cleaned all the battery terminals, only the driver side positive had any corrosion and not much at that... but it was enough to make it overcharge. If it does it again I am ordering a new cable.

 

thanks for the help. You think I need to take the cross over cable loose on the drivers side and check volts? If the cable is bad it could still show the right volts? If ( when) my truck does this again why not put the pos. end of my jumper cables from battery to battery? I think you are right or hope you are right but this would let me be sure before I buy the cable. thanks again and I will post results.

 

I would assume that a bad ground on the driver side battery could cause the same problem.

 

update. The truck did it again so I pulled over and hooked jumper cables to the batteries. It went back to normal. When I was undoing them I saw a spark on the pos. side of the drivers battery. The cross over cable was not making good contact. After cleaning it again and re tightening the cable all is good. I just hope it stays that way. Thanks for the help, I was ready to trade for a different brand. It does look like the dealer would have checked this instead of wanting to replace the emc.

 

With the engine running, measure the voltage on each battery positive post with a voltmeter.
They should have the same reading.
If not then there is bad connection between cross over cable and battery post or bad cross over cable.
ECM monitors driver side battery voltage for charging control BUT the charging cable was connected to the passenger side battery.
Charging current goes to passenger side battery first then to driver side battery.

 

Thanks for the help. I've driven a good 400 miles and it's still all good. If this is a common problem it looks like Dodge has dropped the ball again. I've never taken it my dealer that they diagnosed it correctly.

 

This type of issue is typically associated with onE of the following issues. Check the crossover cable and be sure to clean all of the ground connections. You will likely find the problem to be between the two batteries. You may think that the cable is clean because you wire brushed the corrosion from the cable ends;however, the corrosion tends to creep into the stranded wire under the rubber cable sheathing right behind the cable end. This is what you must look for or it could happen again.

Even a dead drivers battery alone, will cause the same symptom and will compromise the passenger battery very quickly due to overcharging. It is a best practice to replace batteries in pairs.

 

Thanks again.