hi everyone I have been fighting a losing battle with the charging system on my truck, it only acts up when it's below 50 degrees, then the voltage gauge with jump back in forth between 9 volts and 14 volts and the lights flicker with it. the parts that have been replaced ecm, alternator, battery's, checked connectors. I've gone threw it from front to back and even had it at 4 different dealerships and still can find the problem plz help thanks.

 

That sounds it may be your grid heater cycling. Does it only do it after you start the motor?

 

yep it only does it when i start the motor and only when it's cold out. if it's above 60 degrees it will not be erratic.

 

LMAO

Every year without fail!

This is NOT a problem with your truck! Perfectly normal behavior!!!!

It is the intake grid heater cycling.

That intake grid heater uses about 2600w of power... (about 220A) which is far more power than the stock 136A alternator can keep up with. This is the one and only reason your truck has TWO BATTERIES. it does not need two batteries to start... It needs two batteries to stay running and start with that huge power draw from the grid heater during the winter months.


The grid heater will cycle any time the temp is below 60* F outside during key on/starting. it will stop cycling after something like 5 minutes, or when the vehicle exceeds 20MPH, whichever comes first..

Stop wasting your money replacing perfectly good parts. your ECM cycles the grid heater on and off because of the huge power draw... it cycles it off to prevent dropping below a certain voltage level, and to prevent the wires from overheating, and then cycles back on/off in timed intervals..

all cummins trucks do this.

If you don't like it: get a 240A alternator, delete the grid heater, or get a gas motor...