My Heater and Ac fan only works on High

sounds like a resistor switch is bad to me

Where is the resistor switch located?

the resistor block as it is called is usually located in the A/C blower box on the passenger side firewall under the hood . It wil lhave a spade terminal connector with about five or six wires going to it . unless they changed where they put it , but that is where it used to be

Chances are if the resistor is bad the plug and blower motor are the cause. High resistance in the motor causes the resistor to usually burn out.

yes this is the resistor, it is located under the dash on the pasenger side, very easy to get to. Be sure to get a new resistor with the pigtail so you can change the end of the wire that connects to the resister, it is a better version with heat shield, chances are that your wires next to the plug are gone bad to.

And I dont thin it is the motor if it is running fine on full blast. These resistors are known to go in the Durango but not the blower motor.

what about 2002 ford f150 block resistor

I replaced the resistor still only works on high, new switch, new control box on drivers side. New fan motor fuses good

New resistor, new fan, fuses good, new switch