Theres 3 causes for this. First most common your blower motor is on its way out. Second a wiring problem on the blower circuit. Third is an airflow problem around the resistor.The main reason that resistors get hot is that when current passes through it energy is lost in the form of heat. This happens due to friction as electrons bump into each other, as well as the conductor resulting in heat. But, the resistor shouldn’t be very hot to the touch under normal conditions (if its power ratings are not exceeded).
Why do I keep burning up blower motor resistor?
I finally found the simple solution and ultimately the actual cause to the issue of the blower resistor burning out and over-heating the plug wiring - The blower motor itself is the culprit! After years of replacing the blown resister module 3 to 4 a year, I finally bit the bullet and bought a new blower fan/motor.
What causes heater resistors to burn out?
In most cases, a blower motor resistor fails due to corrosion or overheating. Sometimes, the mechanical resistance to the motor rotation causes an excessive electric current that can overheat and prematurely damage the blower motor resistor.
How do I know if my blower motor resistor is bad?
Signs of a Bad Blower Motor Resistor Loss of HVAC fan control (total or certain speeds) The fan only works on its highest speed setting. No air coming from vents. Intermittent or inconsistent fan speed.
Will a blower motor work without the resistor?
Without any power, the motor won't run. As a result, the blower fan stays still and silent, and no air blows out of the vents. There are instances where a bad resistor will prevent the current from reaching the blower motor altogether.
What causes heater resistors to burn out?
In most cases, a blower motor resistor fails due to corrosion or overheating. Sometimes, the mechanical resistance to the motor rotation causes an excessive electric current that can overheat and prematurely damage the blower motor resistor.
How long should a blower motor resistor last?
The blower motor resistor is designed to last for the car's lifespan. In most cases, these resistors will wear out long before the car does. Usually, the wear that the blower motor resistor has is due to the constant use that it gets and the heat that it is exposed on a regular basis.
Does a blower motor resistor have a fuse?
A fuse is often located on the resistor board. The fuse only protects the low and medium blower speeds. High speed will still work if the resistor fuse is blown.
What happens when a resistor burns out?
The resistance value can shift permanently, the lifetime can be significantly reduced, or the resistor is completely damaged resulting in an open circuit. In extreme cases the excessive power can even melt or catch on fire.
What happens if your blower motor relay is bad?
If the blower motor relay develops any sort of problem that hinders its ability to properly limit and distribute power, it may cause the blower motor fuse to blow. Any sort of electrical spikes or excessive current from a bad relay will blow the fuse and cut power in order to protect the system.
Can a bad blower motor resistor cause no AC?
Power to the blower motor is fed through the blower motor resistor, so if it fails or has any issues power can be cut off to the motor. A blower motor without power will not be able to produce any air pressure, and as a result the heating and air conditioning system will be left with no air coming from the vents.
Is there a way to test a blower motor resistor?
Place one lead of the Ohmmeter on terminal 1 of the resistor. Place the other lead on terminal 2 and check against specifications. If this circuit is open, showing infinity on the Ohmmeter, the blower resistor must be replaced. Move the lead from terminal 2 to terminal 3 and check this reading against specifications.
Can a bad blower motor cause overheating?
A bad blower motor will sometimes overheat, causing a “hot” smell to come out of your air vents. In the worst scenarios, your blower motor may actually start to burn.
What does cooling fan resistor do?
The resistor is powered by the ignition and enables the cooling fan to run at slow speed. Once the engine reaches a manufacturer-predetermined temperature, a temperature switch indicates to the cooling fan resistor that the fan should run at high speed to draw more air through the radiator and provide extra cooling.
What is the difference between blower motor and blower motor resistor?
The blower motor resistor is responsible for controlling the blower motor speed. In the past, this was done by varying the voltage supplied to the blower motor. In newer applications, the blower motor resistor is actually a solid state module that sends a varied signal to the blower motor.
How do you test a resistor?
To test individual resistor values (outside a circuit), connect the multimeter probe wires to the resistor's two terminals—it doesn't matter which way round, as resistors are not directional components. Make sure the multimeter dial is in resistance measuring mode. Then check the value on the multimeter.
Why does my blower motor keep failing?
Blower motor breakdown can be the result of anything from old age to failed bearings, high amp draw, electrical failure in the windings, dirt accumulation, and more. “The most common cause is dirt accumulation due to lack of maintenance,” said Tom Beaulieu, president of Bay Area Services Inc.
Can a bad blower motor resistor cause no AC?
Power to the blower motor is fed through the blower motor resistor, so if it fails or has any issues power can be cut off to the motor. A blower motor without power will not be able to produce any air pressure, and as a result the heating and air conditioning system will be left with no air coming from the vents.
What causes heater resistors to burn out?
In most cases, a blower motor resistor fails due to corrosion or overheating. Sometimes, the mechanical resistance to the motor rotation causes an excessive electric current that can overheat and prematurely damage the blower motor resistor.
Should I replace the blower motor and resistor at same time?
We do suggest that you replace the resistor at the same time. It may not be critical, but this will keep the system more uniform. The issue may even be related to the resistor. If you know that it is not related to the issue, then you do not have to replace it.
How can you tell if a fan fuse is blown?
Look at the fuse wire. If there is a visible gap in the wire or a dark or metallic smear inside the glass then the fuse is blown and needs to be replaced.
Can a resistor start a fire?
Some resistors go on fire when grossly overloaded. Some are self extinglishing and some are not. If you have a source that has a very high prospective fault current you must be very careful.
How do you know if a resistor is shorted?
If its two terminals are connected to the same node, the resistor is short-circuited. In practical circuits, we might also say a resistor is short-circuited if a much lower value resistor is connected in parallel with it.
How do I test a blower fan relay?
Connect a test light or multimeter to the ground (black lead). Turn the ignition key to the on position (engine off), and remove the relay. Using the probe, test all terminal sockets in the relay connector. Two of the four should have power.
How much does it cost to replace a blower motor resistor?
How much does a blower motor resistor cost? To replace the blower motor resistor, it would cost you anywhere between $50 to$150 – this includes the cost of equipment and labor. However, by doing it yourself at home, you can save up to $70.
What does a resistor do in a car?
The blower motor resistor in your car is the part that is responsible for pushing air through the vents when using the air conditioner or heater. The blower motor resistor is constantly put under stress which can cause it to eventually fail.
Why does the fan get hot when the fan speed decreases?
The lower the fan speed the hotter the resistors will get. They are many times designed so that they are inside by the blower, so it can cool them. Many times as a vehicle ages, the blower motor bearing start to wear and the motor actually takes more current to operate. The result could be a blown fuse or more often the resistors go bad.
Can a bad fan resistor cause overheating?
If the cooling fan resistor fails or has any issues, it can cause power to be cut off from the cooling fans, which can lead to overheating. Any sort of overheating issue should be tended to as soon as possible to avoid the possible engine damage.
Why is the resistor in the blower so hot?
The resistor is indeed very hot! and you are right it's cool by the blower, that's why most resistors are in the blower case. the fuse was blown because it's not the right amp rating or the blower may be going bad. .
What causes a condenser fan motor to overheat?
There are a few common reasons why a condenser fan motor would overheat to the point that it stops working, such as: Lack of maintenance: This is probably the most common reason that causes condenser fan motors to overheat and shut off. Proper and regular lubrication of the fan motor is necessary for the motor to run smoothly.
Below you will find two interesting articles on a similar topic 👇
Why does my car heater only work on full blast?What causes a blower motor resistor to overheat?
