Heater blower only one speed

SOURCE: 2004 Ford F150 - AC/Heater blower speed 1 & 2 not working.

You might have a bad speed selector switch, or your blower motor resistor is faulty.

SOURCE: I have high speed blower but no medium or low

It's likely a relay. I've often seen where the lower settings are ran through one relay and the higher setting ran through another because of the difference in amperage. I'd start there, the relays are often pretty cheap and a lot easier to replace than tearing the dash apart to change the switch.

SOURCE: heater blower only works on high speed

You probably have a bad resistor, the resistor is located underdash on the passenger side next to the blower motor, remove the wiring harness and screws to remove it and replace it with a new one. The resistor is responsible for blower motor speeds less than full. Hope this helps, let me know.

SOURCE: Location of the resistor for the heater fan speed

right side under dash

SOURCE: I ONLY HAVE hIGH SPEED ON MY HEATER BLOWER, SPEED

blower motor resistor, speed controller