1999 ford expidition air condition/heat switch

-Sounds like the system is clogged or the on off valve is not open
properly.
-Check the valve and flush the system. It should be good to go.

Good luck

Mai

it needs to be reconditioned, ater that recharge with required refill kit

Ignition switch may not be feeding power to AC clutch and/ or radiator fan circuit.

Your problem is a faulty heater control valve. The design used on these vehicles allows for hot water to flow constantly and compete with the evaporator as there is no blender door. You have to replace the valve and possibly the control head. Meanwhile, you can bypass the valve to have cold air

Sounds like a broken or cracked vacuum line under the hood.

The A/C system has a pressure switch will keep the A/C from running if the freon is low. It prevents damage to the A/C compressor from low freon.
My bet is you'll need to recharge the A/C system.

I know from experience that if the coolant is to low ( not just the freon levels in the compresor but the antifreeze/coolant level as well) the AC system will not cool and will blow hot. Check the coolant Antifreeze and freon levels, even with the Coolant being a little low my 1998 Ford E150 Van will blow hot. After you have ruled out of these possibilities and the chance it is the thermostat most likely the problem is what Ford calls the "Flap" it controls the air flow through the vent system when you switch from Heat to AC. When the Flap is working it closes off one systems air flow so as to not interfere with the current climate selection.

where is the heat blend door located 97 ford e-350 van

IF U ARE TRYIN TO GET THE HEAT U CAN DO 3 THINGS
1. TURN HEATER ON THE FACE/FEET POSITION AND PLACE ON HIGH, TAKE THE RADIATOR CAP OFF AND CONTINUE TO POUR WATER/COOLANT UNTIL HEAT GETS HOT
2. CHECK/REPLACE THERMASTAT
3. CHECK/REPLACE HEATER CORE

This is a redundancy thing in the climate control system. You'll want to take the console apart and check the connectors behind the climate control panel. I was installing a stereo in mine, and when I started the car (with the climate control disconnected), it did exactly what you're describing.