when is it time to plug them in?

 

Well ya got to options A when it dont start or B when it gets hard to start next time it gets about that cold its time to plug it in. Id get a heavy duty timer tho and set it to go off about 2 hours before ya want the truck to start. I dont no what the 7.3 engine uses but my 6.9 uses a 600 watt heater wich draws quiet a bit of power and can really make the meter hum.

 

thanks its been getting in to the 20 i have had no hard time starting my truck it starts everytime no problem thats why i was asking. thanks

 

No problem Id tell ya a more excat temp to plug in but it varies quiet a bit between engines i guess its were ya park wether its in the wind or not how it was driven etc etc

 

Thanks I did not know all that had to do with it

 

The relative humidity seems to have an affect on mine, if you travel somewhere wet like oregon, bring your ext cord. Mine will start down to 10 degrees without plugging in if the gloplug system is working properly, but I usually plug it in for 3-4 hours when it starts to get below 30, it runs smoother and seems to be less wear and tear.