My heat only works on high on my 98 windstar - 1998 Ford Windstar

codes are OBDll and are available online free
P0174

• Intake air leaks
• Faulty front heated oxygen sensor
• Ignition misfiring
• Faulty fuel injectors
• Exhaust gas leaks
• Incorrect fuel pressure
• Lack of fuel
• Faulty Mass Air Flow (MAF) sensor
• Incorrect Positive Crankcase Ventilation (PCV) hose connection
• P0171
• Intake air leaks
• Faulty front heated oxygen sensor
• Ignition misfiring
• Faulty fuel injectors
• Exhaust gas leaks
• Incorrect fuel pressure
• Lack of fuel
• Faulty Mass Air Flow (MAF) sensor
• Incorrect Positive Crankcase Ventilation (PCV) hose connection
• P0102
• copy and paste
• https://www.justanswer.com/ford/2dnqt-98-windstar-dtc-p0102-sitting-trouble-code-mil.html

copy and paste
https://www.justanswer.com/ford/8kg47-ford-windstar-code-p0302-p0305.html

P0453
copy and paste
https://www.justanswer.com/ford/3qxa3-getting-po453-code-evap-pres-sensor-high-99-windstar.html

I had the same problem with my 98 and the signal lights switch on the steering column was bad

check the white plug on top of the transmission for contamination or loose/corroded connection

maybe the actuator behind the radio that controls the hot and cold air ..$50 part

try changing the thermostat for starters.

would be best if you did lest hassel with electrical

intake manifold may be leaking and cause rough idle pretty big job check for leaks heat could be heater control valve faulty or not getting vacuum its located near firewall under hood on pass side i think u will see 2 coolant hoses going into car firewall feel hoses also should get hot heater valve will be connected to 1 of the 2 hoses

If you have the heater directed to the windshield, the AC will turn on. Move the control away from defrost.

first of all check to make sure you put back the correct amount of fluid and then do this start the car up and put antifreeze in it and let it run till it gets to temp you may have an air bubble in the system then put the cap back on right away check the condition of the drive belt

make sure it has plenty of coolant in it if it is low the heater wont work. is there any water in the passenger side floorboard