front fan speed on high or off.....only option..... ford expedition 2003 mod

[Grungemaster]

Struggling finding the root cause for dysfunctional fan speed front climate control. I have changed the motor blower resistor and the control unit, but the fan is still only working on high speed. It is either on high or off.


Anyone have any suggestions for where to look next?

 

[stamp11127]

If it is manual controls each fan speed setting sends power to specific points of the blower motor resistor. Check for source voltage for each setting at the blower motor plug.