Nissan 300ZX Heater Blower Motor Resistor Replacement Cost

The blower motor is a fan housed in the heating ventilation and air conditioning (HVAC) ducts, normally located behind the glove box. This uses a blower motor resistor to change the speed at which the fan operates.

The air conditioning and heating controls allow the user to switch fan speeds, allowing the fan to spin faster or slower. It has this capability because the fan uses the blower motor resistor. The blower motor resistor is between the power source and the fan, and allows only the desired amount of power to go to the fan. When the fan receives less power, it turns slowly, and when it receives more power, it will speed up. This translates to the amount of air that is blowing out of the vents.

When the blower motor resistor fails, the air conditioner and heater may still work, but heat or cool may blow from the vents on some of the fan speed settings. In some rare situations, mostly after long periods of partial blower motor function, the blower motor resistor may fail completely, leaving the entire HVAC system useless.

Driving with a defective blower motor resistor may not be the most comfortable option for occupants, but there is no safety risk associated. The blower motor resistor contact cause other components to become damaged, and has no moving parts. If it has failed completely, the temperature in the vehicle will be completely unregulated.

Blower motors resistors tend to fail frequently in high mileage vehicles, but their failure does not depend on mileage. Age can be a factor as the plastic can become brittle over time, or heat may cause electronic failure. The amount of use a blower motor receives may also be a factor.

The servicing technician will perform a series of tests that will lead them to the blower motor resistor. If the blower motor is not blowing air on any setting, the technician will first find and inspect any related fuses. Afterwards, the blower motor resistor electrical connector is inspected to determine if power is reaching the blower motor resistor. If power reaches the blower motor resistor, the blower motor does not receive power, the blower motor resistor is probably faulty. It will be removed, inspected, and bench tested with an external power source.

If the blower motor resistor must be replaced, either the glove box or lower cover will be removed from the dashboard. This will grant access to the HVAC duct box, and the blower motor service cover. The service cover is removed, and the blower motor resistor is disconnected from its’ electronic connectors. Finally, the blower motor retaining screws will be removed, followed by the blower motor resistor. Installation will include installing the blower motor resistor into the blower motor, followed by the reverse order of operations for removal. The technician can then test the function of the blower motor, and confirm the customer complaint has been resolved.

We do not recommend immediately suspecting the blower motor resistor of failure when the symptoms that were mentioned occur. Testing is imperative to making a proper diagnosis, and replacing parts becomes costly very quickly. We recommend disconnecting the battery any time there is an open electrical circuit, as arching to the vehicle chassis can damage sensitive components.

If the blower motor is making a grinding or rattling noise, the blower motor resistor is typically not at fault. When some of the fan speed settings stop functioning, it is considered safe to use on the remaining settings, as those circuits have not suffered failure. Until the vehicle is repaired, further use should not complicate the issue. When all fan speeds are not functioning, the blower motor will be suspected, and the blower motor resistor may be tested in the process.

The moderately skilled DIYer can accomplish this diagnosis and repair. A basic understanding of a series electrical circuit, a few basic tools, and a digital voltage meter are all that is required. It is important that the DIYer understand the testing procedures for the blower motor circuit, as failing to properly test the blower motor may lead to unnecessary costs.