hey everyone, i have a 2004 ram 3500 cummins that was over charging at about 15.1 volts, so i installed an external regulator properly grounded to the alternator, wires to keyed power and soo on. It works great putting out 14.7volts, my problem now is when i get about 30mins down the road the voltage gauge on the dash goes all the way down to 0 (or 8 if you prefer) but using a multimeter at the batterys while the trucks running it still shows 14.7volts. Once i turn the truck off and starting it again after an hour or soo the gauge will work perfectly and drop out again after 30mins... Please help and thank you in advance

 

Did you leave the stock wiring connected when you installed the external regulator? Have you tested alternator output when the gauge is showing nothing?

 

 

Hhhhmmmm....... I need wring diagrams. Not familiar with how the system is supposed to work on the newer trucks.

 

Not sure about the 04, but the voltage is controlled by the PCM on my 08 as are the gauges. Not sure about pre-CANBUS trucks.