Greetings all. Have a weird problem with my Super Dodge.

Sometimes it seems to charge normally. Meter says it's making about 14.2 Volts. Seems a bit high.

Then, from time to time, it won't charge at all. After a few seconds to a few minutes of running, with the Volt Meter showing about 12.5 volts, the meter will swing to 8V, and the Check Gauges light will illuminate.

This has been going on for a week now. First day it happened, I looked under the hood, and the passenger side battery had acid on the top of it. I bought a new battery, but that wasn't the problem. New battery looks like it may have acid on it recently too, now.

Load tests on both old batteries and the new one show that they are 'like new' strong, so no problems there.

So, I bought a new alternator and installed it this weekend. No changes. Sometimes it charges, sometimes it don't, and the gauge goes to 8V and the chime/Check Gauges light comes on. They guy at the parts store said that the engine computer functions as the voltage regulator, so I haven't replaced that.

Anyone know what might be my problem?

Peter Straub

What is the temperature in the mornings? My volt meter will drop pretty low when the grid heater is cycling on and off...

14.2v seems about right for a vehicle under normal operation. Dropping down to 8v and having the check gauges light come on does not however. Looking at schematics, it appears that the gauges in this truck are all run off of a data link wire. I'm not sure if this includes voltage however... Do all the other gauges work when this happens or not?

I doubt if it is a battery issue. I would be more inclined to think there is a gauge or gauge cluster problem. What kind of voltage is the alternator putting out at the batteries when the gauge is reading 8v?

they also do this to protect the electrical system. i drained both my batteries via a short on my trailer over night. jumped the truck and it would charge high at 14.5 or so for 10-20 minutes then drop to 8 turned out it was the system sensing the batteries requiring too much change. hooked it up to my code reader cleared the codes no more issue. except a week later when the batteries died completely and i had to put new batteries in. even after installing the new batteries it didnt quit with the high charge no charge thing till i reset the computer again with teh code reader.

I'll try the clearing the codes and see if that helps.
I was playing with it a bit last night - I had a 4 hour trip out of town. It's a weird thing very much like a computer problem. If I reboot it (turn the engine off, then on), sometimes it works normal. Sometimes it don't. Sometimes I have to reboot it a dozen times, but once it starts charging, it's fine until I reboot again.
Peter Straub

Personally, I wouldn't be so quick to blame the ECU until you have exhausted other options. Basic electrical troubleshooting still is important in this day and age...

Again, do all the other gauges work or do they all go to zero when the check gauges light comes on?

Have you verified whether or not you actually have alternator output charging the batteries when the volt meter reads 8v and the check gauges light comes on?