When the heater or air conditioner in your car is turned on, the fan turns on pushing the air from the car vents. The motor that spins that fan is called a blower motor. It is located inside the dashboard usually on the opposite side of the steering wheel or the inside of the engine compartment on the firewall.
In almost every modern car out there, the blower speed can be adjusted. Some cars have blowers which have 4 to 5 fixed speed settings, which can be chosen but in this case, the speed of the blower motor is controlled by a blower motor resistor.
What is a blower motor resistor?
A blower motor resistor is an adjustable resistor. This electric component is used to regulate a vehicle’s air conditioning system, it is the part that controls the blower motor’s fan speed according to the settings which can be changed by using the knob and turning it left or right which would increase or decrease the resistance of the flowing electric current to the spinning blower motor connected to the fan.
As a part of our comfort and luxury the fan speed is one of the most tweaked settings in a car and so the blower motor resistor is persistently put under stress which can eventually cause it to fail, excessive humidity in the atmosphere can cause an increase in resistance. Because of this, the blower motor resistor may create issues with the whole heating and air conditioning system.
Even though it is unusual for this motor resistor to go bad, almost every component, apart from a few, fail at one point or another, after which they either need to be repaired or replaced completely. Fortunately, in this case, the motor resistor isn’t a high tech piece of electronic and can be replaced rather easily and inexpensively. Diagnosing a failing blower motor resistor is actually easy too, and doesn’t require any special skill or even basic knowledge as the resistor serves a single purpose – to limit the blower to different speed settings. A faulty blower motor resistor will usually produce these symptoms that can be identified.
Heater Blower Motor Resistor Symptoms
No air blowing through vehicle’s vents
Commonly, upon turning on the blower while operating either the air conditioning system or heating, if the blower fails to turn on at all, it’s usually not the blower itself or even the resistor, but sometimes it is the resistor only. Since the blower resistor is directly responsible to transfer the power from battery to the blower itself, a symptom of the faulty blower motor resistor is that no air flows from the car’s vent. The blower motor resistor is responsible for powering the blower motor directly, so if it fails major issues in the heater and air conditioning system as if the Power is completely cut off to the motor due to overheating or corrosion the motor would simply not work, which would leave the whole heater and air conditioning system useless with no air flowing through the car vents.
Blower motor only working on high speed
A common symptom of a faulty blower motor resistor is when the heater and air conditioner fan only works at high speed and can’t be adjusted to low speeds. This occurs due to the failed blower motor resistor not being able to control the flow of electric current, it could be that the resistor is somehow bypassed and the power is directly being fed from the switch. Excessive current can overheat and permanently damage the blower motor resistor
In this case, the heater and air conditioning system may still function normally pushing the cold or hot air out of the vent beside the speed. The resistor needs to be replaced with a new one in order to restore its function.
Blower motor only working on low speed
Another common symptom of a faulty blower motor resistor is that the blower motor only works at slow-speed. This can be caused because of bad wiring between the blower motor resistor and the blower motor itself.
Blower motor doesn’t work in certain settings
Another symptom of a faulty blower motor resistor is that the blower motor is not able to work on some settings. This causes the blower motor to malfunction or not function at all in one or more settings. It is highly probable that the blower motor switch has stopped working.
A proper diagnosis is highly recommended if you are uncertain of the issue
Smoke coming out of the vents
If you notice smoke or burning smell coming out of your vents, it could possibly be because of the overheating of the blower motor resistor which could have burned some wires inside of the dash.
It’s best to stop the car immediately and investigate further damages and let it cool down.
Solutions & Testing
There’s not much you can do to fix a bad blower resistor as it’s better to replace it completely. If you feel comfortable with trying to replace the resistor yourself, you can find out where the component resides and how to test it.
Steps to check/test the resistor:
Find the blower resistor and detach it from the rest of the circuit, Once the resistor is positioned and detached, it is often possible to say whether or not the resistor has burned out or not judging by simply looking at its condition. A burned out resistor needs to be replaced via the correct alternative.
If the appearance is normal, it is necessary to a degree the resistance throughout every individual resistor. The resistors are all linked to a single common point. Switch the multimeter to the resistance measuring mode, connect one probe of the multimeter to the commonplace point and use the other probe to degree resistances at other points. If any of these resistances show an open circuit, then the blower resistor desires to get replaced.
Heater Blower Motor Replacement Cost
Know what fee you should pay to get your automobile constant. The average cost for a blower motor resistor substitute is between $80 and $150. Labour costs are envisioned among $35 and $80 even as elements are priced between $50 and $75. The estimate does not consist of taxes and charges.