dieselman2300

The fuel heater ONLY turn on when the key is ON according to the FSM.

I dont run the fuel heater anymore, because I have an AirDog now. This winter it got close to -20*f here, and my truck started and ran without the fuel heater everyday.

FWIW, if you run a good additive with an antigel in it, there should be ZERO problems with you fuel gelling and/or waxing.

busa

I have a full FASS unit so no heater, temps down to -40 never has gelled or stumbled. I do add anti-gelling additive more when its really cold.

Dartmouth 12V

The fuel heater will only turn on when the key is in the on position and the temperature is cold enough(I can't remember how it decides this). It will not help with cold starting since it is so far away from the injection pump(there is a filter and all of the fuel in the pump itself and lines before it gets to the injectors).

Yes, the fuel tank does get warm after a while. However, on extremely cold days when you are traveling at freeway speed where there is more airflow by the fuel lines to rob them of their heat, you can have gelling problems. It has only happened once but I saw my fuel pressure falling and I plugged back in my fuel heater and it climbed back up to normal.

Since the preheater does nothing normally, you should unplug it so that it does not burn up and create air leaks. Then, if you ever start to gel, you may be in luck if you plug it back in.

dieselman2300

According to the FSM,

"The fuel heater is equipped with a built in thermostat that senses fuel temperature. When the temp. is below 40*f, the built in sensor allows current to flow to the built in heater element warming the fuel. When the temp. is above 80*f, the sensor stops current flow to the heater element."

Like I said before, if you treat your fuel with an anti-gel additive, your fuel wont gel and/or wax.
Common Sense with a diesel.

dieselman2300

Another thing,
I would say out of the 50+ Diesel trucks on the job, only 25% of the guys use an additive, let alone an anti-gel.

Big Blue24

Ok, well in that case, get rid of it! Sounds like it does nothing.