Got a 2011 xlt. Last year had the single speed blower problem. I replaced the resister and was fine. Now I got the first 3 speeds working fine. If I go to the fourth, I get like a loud hum and blower stops. Go back to any of the 3 and it's fine. Any ideas?

 

Was it an aftermarket part?

 

No, Motorcraft. I stick to that. On rare occasions It might run on the 4th speed but after going but back to a lower speed then 4th, I'll get the humming sound an no fan. I'm wondering if on the resister the connection or however you call it is defective. The new one will here tomorrow.

 

Going to add something else. If the truck sits for an hour or more off, when I start it up and run the fan on high (4th) it will run. But after driving for a few minutes and try another speed then try 4th, it goes back to humming.