Your truck has no glow plugs, just a grid heater, a/c block heater and a heater in the filter housing. My grid heater will still come on when its in the low 60's. you can hold the odometer (trip meter) reset button in and turn key on for a light test.are you guys talking about the glow plugs/wait to star light, if so it should only come on when i think its below 50 degrees. Then you have two other heaters the engine block heater, which only comes on when you plug it in and the grid heater which allows warm air to enter the intake manifold thus warming the engine sooner. The only way you can tell if its on is you can watch your lights dim and you voltmeter will drop and raise. Hope this helps you all out.