A heater resistor pack is used to control the speed of the two blower fan motors. In some vehicles the heater resistor is also used to control the air conditioning in a vehicle. Some SUVs or vans have a separate heater resistor in the front of the vehicle and one in the rear as they have two heater systems in the vehicle. The pack is a useful buy for one of these vehicles.
If a heater resistor fails, you may find that the heater fan will no longer blow on one or all of its speeds. If the blower motor is causing problems, you could notice that using the vehicle’s heating or air conditioning system is noisy, which could be caused by a failing heater resistor.
When inspecting a failed heater resistor, you may notice some points on the resistor that are burnt. This could be caused by an unnatural amount of load on the heater resistor fan. This could be caused by insulation from around the fan being dragged in to the fan, causing it to struggle to turn freely. Failure can also be caused by the bearings of the fan becoming damaged, resulting in excessive draw.