I have an '09 3500 6.7 with a new problem. Recently, whenever it is below 55 degrees in the morning, my grid heater begins cycling as soon as the truck is started. This is new as it never cycled in the past until below 40 degrees. If the grid heater cycles, I have to wait 10 to 15 minutes to put in gear and move...otherwise the voltage light and check engine light come on. This hasn't been a huge issue as it would run fine and the lights would go off after the truck was shut off and sat for at least 8 hours. Today, though, lights came on and after a few miles, engine started surging and then dropping to nearly zero rpm with little control. Thoughts from anyone appreciated.

 

Amanda, I have an '08 3500 6.7. For your grid heaters to cycle on at 55 degrees is normal. The temp inside your intake is probably colder. It shouldn't take getting down to 40 degrees for your grid heaters to cycle. My voltage light has never come on during this procedure but my voltmeter does drop down to 8 volts during the cycle but stays on shorter and shorter each time it cycles. My MIL or check engine light has never come on due to cycling grid heaters and you shouldn't have to wait 10 - 15 minutes to get rolling. Every time your check engine light comes on your computer should store a retrieveable code which can be read with an OBDII scanner or if you don't have one there is a procedure given in a post today for retrieveing them using your odometer. I should add that instead of the 600 amp maintenance free batteries I have the 750 amp batteries which might make a difference with the load on them at start up. I know this doesn't directly answer your question, but it might help you find the answer.

Rickywa

 

I think you should get your batteries load tested and/or replaced. I have a 2007 and replaced them with some 1100+ amp models...

 

Yes, have them tested separatelly by disconnecting one battery terminal. Replace both if one bad.