I have a 2009 F-150 King Ranch with 5.4L. My blower motor runs continuously. This started about a week ago. I've already changed out the blower motor resistor, which according to my research is the most common problem, but that didn't fix the issue. Anyone else experienced this or have any suggestions on what to look at next. Thanks,

 

Do you have any idea if it is running at high speed or some other lower speed.
In either case you might start with carefully checking the blower motor switch to make sure it has not overheated and is now sticking in the on position internally..

 

It seems to be running somewhere between medium and high. How would I go about checking the switch?

 

It seems to be running somewhere between medium and high. How would I go about checking the switch?

 

You could try checking the power and ground at BOTH, the resistor and at the motor itself.

The other way is a little more work and it would require removing some of the dash covering to gain access to the switch.
Not knowing your level of expertise , you might consider having a shop do this.

There were problems in the past due to the heavy demand for power for the blower motor that caused the blower switch assy to overheat and self destruct