When I turn the fan speed to 4 the fan turns off, any ideas where I should look to try and fix?

[sonicsprings]

Maybe one of the cables behind the knob popped off? Speeds 1-3 all work fine

 

[ozonetrooper]

It could be the blower motor resistor.

blower resistor/click here

 

[michael1974]

Did you ever get it to work on 4