Welcome to the FMCA forum!
Think you are referring to the dash heater. That being the case, there are hundreds of different styles and sizes. The problem is often the electrical wiring. Switch, resistor array, relay or fuse.
So could you see if you can find some information regarding the blower motor.
First some questions. Does the fan run on some speeds and not others?
Then can you determine if the problem might be the speed selector switch? or the resistor array, generally in close proximity of the motor its self.
The motors are frequently located on the passengers side behind the kick panel in front of the passenger seat or outside on the firewall passenger side.
I will look and see if I might have some wiring information in the mean time.