Ford Repair: AC/ heat fan blower, heat fan, fan blower

Question
My neighbor 96 ford explorer fan work intermittently. When he turns the air /heat on /off switch it some times will work for a few moments or if he is lucky until he turns off the car.  Are there any checks to determine which switch is bad?  

Answer
you could go to the blower when it is acting up and tap on it if it starts to run could have loose/dirty connections but most likely it would be motor-you can also check power and ground at motor if none there probably a switch or resistor but resistors don't ususally come and go so switch would be most likely cause.