On page 89 of the owners manual under "C" there is this statement "Turn the temperature control to maximum heat to turn on the auxiliary heater". On page 195 fuse link "H" describes a 80 amp fuse for "Positive temperature coefficient heater"
Does Transit have an electric air heating element for the dash air vents? My 08 Sprinter had a 1000 watt air heater that would start automatically when warm air was selected and would shut off automatically when interior warmed up. I could see when it stopped by the change in volts shown on my Scan Gage. Voltage would jump up 1/2 volt when it turned off.
If I knew how it functioned, I could avoid turning on the "vehicle" powered 1000 watt inverter when Ford heater was operating. Hopefully Ford electric heater is not automatic and only comes on if heat selector switch is at max. setting.
It is not all it is cracked up to be. I have no heat at all until I start driving but my defrost works. So letting it run for 15 minutes to warm up the interior does not work. It has been like this since brand new so it is not a clogged heater core.