It is a hot summer day, and you are stuck in traffic for hours. You try to turn on your AC, but you don’t feel that it did anything. You don’t hear the AC working at all. You need to crank the AC to the max before anything happens. If this is the case, you may have a problem with the blower motor resistor. You should know how to bypass the blower motor resistor for a quick fix.
So, how to bypass the blower motor resistor? First, you must know that the problem is in the blower fan resistor. You would need to test and check it with the multimeter. You can skip this step and bypass the resistor by changing the blower motor’s speed to the maximum. But we recommend solving this problem as soon as possible.
A list of symptoms can point to a problem with the motor resistor. We will go through all the problems that can cause a problem with the resistor. Also, we will cover the topic of testing the resistor. That can save you a lot of money, and you can find a problem yourself. This way, you will know if you have a problem with the motor, resistor, switch, or other component. Stay with us!
What Is Blower Motor Resistor?
The blower motor runs the fan in the air conditioning system in a car. Usually, it is located inside the dash, on the opposite side of the steering wheel. Sometimes it is placed on the firewall of the engine compartment.
A blower motor resistor is a part that is that controls the speed of the blower motor. This way, you can choose at what speed the AC will work. In most modern cars, it is located behind the passenger side of the dashboard, in the HVAC housing.
A blower motor resistor is a part that is that controls the speed of the blower motor. This way, you can choose at what speed the AC will work. In most modern cars, it is located behind the passenger side of the dashboard, in the HVAC housing.
What Are The Signs Of a Faulty Blower Motor Resistor?
Any problems connected with the AC and airflow can be connected to a faulty blower resistor. If there is no air when you flip the fan switch, or you cannot select the fan’s speeds, you should check the motor resistor.
Some problems are connected to the blower motor, and some with the switch, but these are all common symptoms. You should start checking the resistor and the wiring harness. If there are no problems there, check the motor and other components.
Blower Motor Only Has One Speed
If you cannot change blower speeds, that can point to a defective blower motor resistor. In most cases, the fan will work only at the highest speed. It will get the power from the switch.
This malfunction happens when the resistor fails or short circuits, but also check the connections to the motor and the fan switch.
Some Settings Are Not Working
If some settings of the AC don’t work, that can be traced back to a bad blower motor resistor. If you are not sure what the problem is, you should also check the blower motor switch. A faulty blower motor switch can cause several blower issues. Check the whole system for problems before you replace the resistor.
Vents Are Not Producing Any Air
If the air is not coming out even on the highest setting, that is a sign that the motor resistor doesn’t work at all. If the resistor is not working, then the blower motor cannot receive any power. Before you change the resistor, check the blower motor resistor fuse. A blown fuse can also cause this exact problem.
Check Out the Symptoms of a Bad Blower Fan Motor Resistor:
Common Reasons For Blower Motor Resistor Failure
Besides regular wear and tear, the motor resistor usually fails because of overheating issues. Use the AC properly, and monitor its work, so you can avoid expensive problems.
Overheating
If the fan blade is jammed by a foreign object or the fan bearings are worn, the motor cannot rotate freely. Then the excessive electric current can cause a resistor to overheat.
Clogged Air Filters
If the air filters are clogged, the whole AC system must work harder. That can lead to damage to several components, including the motor resistor.
Frequent Fan Speed Changes
Each time you change the AC settings, the components are under stress. Frequent and unnecessary fan speed changes will shorten its work life.
Faulty Wiring
Any internal wiring issues can cause the failure of the motor resistor. Those issues can be loose wiring or problems with rust.
Wear and Tear
If the AC is used frequently, it will work shorter. The work life will be shortened if the system has more stress. To avoid these problems, do a regular checkup of the system, and replace everything on time.
How to Test a Blower Motor Resistor
You will need a multimeter and the test light to test the motor resistor. Before you start with the testing, conduct a visual check of the resistor. If there is rust and burns on it, that is a definitive symptom of a defective blower motor resistor.
Locate The Blower Motor Resistor’s Fuse
The blower resistor thermal fuse is usually located on the resistor board. Note that the fuse only protects on the low and medium blower speeds. If the fuse is blown, the AC will still work on the fastest setting. Test the fuse with the ignition key turned on. For this test, use the 12-volt test light.
Attach the clip lead of the test light to the ground. You can use a bolt screwed into metal. Touch the sharp probe end to the terminals on the fuse. If there is an electrical current at both terminals, then the fuse is good. If only one end has power, the fuse is bad.
Test The Motor
Unplug the motor and test it using the same test we mentioned in a step before. Test the power at all engine speeds. If the resistor is faulty it will lose power when changing the engine speeds. The blower will have power at the highest speed because it will get power from the switch.
Examine The Blower Motor Ground
Grounds of the most blower motors are pulled through the case of the motor. This can cause the grounds to corrode or become loose. That will impact the overall work of the motor and create problems. You should test the motor ground if there is direct power at all AC settings, but the motor is still not functioning.
Is it Possible to Use Blowers Without Any Resistance?
If the heater blower has a dead blower motor resistor, the motor can’t work. The only setting you may be able to use is the highest value. Then the heater blower will get power from the switch.
How To Bypass Blower Motor Resistor?
Turn the fan to maximum power and bypass the motor resistor. The motor on this setting will receive power from the switch.
How Much Does It Cost to Replace a Fan Motor on an AC Unit?
The price of the fan motor on an AC unit depends on the model of the car. It can vary between $300 and $400. The labor price is similar so the final cost can go up to $800.
FAQs
Will a blower motor function without a resistor?
It can work on its highest setting. When it is on the highest setting, it bypasses a resistor and gets power from the switch.
Is there a fuse on a blower motor resistor?
Yes, there is, and it is usually located on the resistor board.
Does the blower motor resistor control the speed?
That is the primary function of the resistor. When you change the temperature, the resistor transmits the signal to the blower motor. Once the motor receives the signal, it will speed up, or slow down, depending on the signal.
What is the first sign of a faulty blower motor resistor?
When you notice that the AC works only on the highest setting, that is the first and most certain signal of a bad blower motor resistor.
Final Considerations
Bypassing a blower motor resistor is okay if you need the AC immediately. But, in the long run, you should replace it. If there is a problem with the resistor, other AC parts can also have an issue. We will always recommend keeping every system of your car in check.
If you want to prolong the life of the resistor, use the AC normally, and don’t put it under severe stress. Do a regular checkup of the AC, and minimize its maintenance costs.
