90% of the time it is the temp mode door actuator located in the driverside rear of the truck
The selector switch needs to be fixed or replaced.
possibly low on freon or a blown fuse
the heater blows warm air when fan is on low but blows cold air when fan is turn to higher setting
Low coolant? Bad thermostat? Heater core plugged, restricted or airbound? Bad heater control? Water pump not circulating coolant?
chock
The 1999 Ford Transit cold start wiring diagram can be obtained from most Ford dealerships. The wiring diagram can be found in most Ford repair manuals.
Needs to be charged. 134a You might have a leak.
diagram for 1999 chev subarban air conditioner
The 2007 Ford Expedition Owner Guide shows : For the battery : BXT-65-650 or BXT-65-750 ( if equipped ) So that's BCI group size 65 ( 650 or 750 cold cranking amps )
It came from the factory with a ( 650 ) cold cranking amp battery , according to the Owner Guide
According to the 2000 Ford Expedition Owner Guide : Both the 4.6 and the 5.4 came with the ( Motorcraft BXT-65-650 battery ) * that's BCI group size 65 , 650 cold cranking amps
Sounds like it is low on coolant.