I don't know why they keep coming on. Its in the mid to upper 40s here, I can turn the truck off after running for 20 minutes, turn it back on and the grid heaters kick on. If I let it set for a few minutes they will kick back on. Why? I figured once it was warmed up, if I turned it off for a second it would still be warm and not trigger the grid heaters.

 

If the IAT reads a temp lower then 66*, it will trigger the grid heaters.

 

Mine does the same thing.

 

Every time you start the vehicle it will restart the cycle. I've been hauling heavy for 500 miles, I have to wait to cool off turbo then shut off. When I restart it will cycle grids again.