The blower motor resistor is a vital component in a vehicle’s heating, ventilation and air conditioning system. The blower motor forces the hot or cold air through ducting and the interior vents. The resistor is the component that regulates the speed of the blower fan by reducing voltage going to the fan. It enables the variation of the setting of the blower motor. It lets you reduce the amount of air that comes into the interior car, instead of just having a blast of hot or cold air the highest possible setting. The blower motor resistor is situated between the vehicle’s heater or air conditioner controls and the blower motor. It is typically found attached beneath the dash. There are two main types of blower motor resistors. The wire-type is typical for older cars and uses different sized coils of wire for each fan speed. Transistorized blower motor resistors are found in more modern cars and utilize a circuit board. For the majority of vehicles, the highest setting for heating or air conditioning bypasses the resistor altogether, giving the fan full voltage. If the blower still operates on high, but won’t operate on any other speed, there is probably a problem with the resistor. Since the resistor draws a great deal of power from the electrical system, it gets very hot. A blower resistor can melt part of the wiring and then fail to work properly. It is not terribly difficult to replace a bad blower resistor as a do-it-yourself project. If you have a screwdriver or a wrench, you can unbolt the resistor from the HVAC ducts. To gain access to the resistor, you’ll probably need to remove the glove compartment. If the component is melted, the replacement project might be a bit more involved. Since soldering might be required, you may want to seek out the help of a professional.