Motor head question
 

I have a 2010 ford f150 king ranch. The other day the blower on the AC broke and kept it in the high position. Ac works greats, just the fan does not adjust levels. I have tried all the relays and all fuses associated with the Ac fan/blower.
Any further suggestions,

2010 is it still under warranty? I'd bring it to dealership if it is!

Sounds like you may have a bad blower module which controls fan speeds if its stuck on high only.

Have 39k miles. Warranty ended at 36k.
Where would the blower module be? In the dash?

There's a resistor next to the fan. I forgot what its called. That's what needs changing.

2 screws and that's it

With so many modules and possibilities, it may be worth taking to a shop. I know some good independent shops that could help you. Just think, one module may cost $300+. If you replace it and, that's not the problem, you can't return the now used part and you've still the problem as well as some higher blood pressure!

If it works on high & stops working in the other fan positions then more than likely its the blower module which took the place of the resistor years ago, still has 2 screws holding it in & will be close to the blower motor.

Tex dawg is 100% correct. Used to be called a resistor, now it is a blower module.

$78.00 labor was $75.