How do I check the temp control switch on a 98 f150 - manual heat. There are 3 prongs on the back. What test can I do to confirm is not the switch.

 

What are you trying to confirm (or not)? That it is a temperature control?

It's just a potentiometer.

 

I got out the mutlimeter this moring. There are 3 prongs. No matter the dial position the meter reading is the same. I assume the center 1 is the hot connection and the outer ones control the door depending on voltage.