If the resistor shorts or fails, it may cause the blower motor to remain stuck on one fan speed. The heating and air conditioning systems may still function at one speed, however the resistor will have to be replaced in order for full functionality to be restored.
Can you bypass a blower motor resistor?
In the highest speed state, the blower resistor is bypassed completely and the fan is connected directly to the car's battery, which allows maximum current through the motor. 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.
What does a resistor do on a blower motor?
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.
What are the symptoms of a bad blower motor resistor?
If the airflow from the vents is weak ...
If you try to increase the air pressure and you feel no difference in the pressure blowing, then your blower motor resistor may be failing. A damaged blower motor resistor will work on one fan speed which may not be enough to keep the inside of your car cool or warm enough.
How do I test a blower motor resistor?
Blower Motor Resistor Testing
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.
Can you bypass a resistor?
A wire in the left circuit is shorting the 100Ω resistor. All current will bypass the resistor and travel through the short. The voltage across the 100Ω resistor is going to be zero.
What does a final stage resistor do?
The final stage (or blower motor) resistor controls the speed of the blower motor in your heating & air conditioning system . Faulty resistors can cause a list of erratic issues, from the fan running when the car is off, to only having one fan speed available.
What happens when a resistor fails?
When a resistor fails, it either goes open (no connection) or the resistance increases . When the resistance increases, it can burn the board, or burn itself up.
How much does it cost to replace a blower motor resistor?
The average cost for a Blower Motor Resistor Replacement is between $108 and $137 but can vary from car to car.
Can you repair a blower motor resistor?
The resistor module is easy and inexpensive to replace. It's then typically installed in the ductwork, near the car blower—either under the dash or under the hood. (Refer to a service manual to locate yours.) Purchase a new resistor module at the auto parts store (usually less than $25).
How long does it take to replace a blower motor resistor?
takes about 45 minutes .
What happens when blower motor relay goes 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.
What can cause a blower motor to stop working?
In a situation where the motor doesn't work on any speed, the most likely causes are: a blown power supply fuse , a bad motor ground connection, bad motor speed control module or a failed motor. On all systems, a failed blower motor is least likely.
Can a blower motor resistor be tested?
If you want to do a quick test of the blower resistor, you can check the resistance of each of the resistors with a multimeter as follows: set the tool to read ohms (a measurement of resistance) and connect one of its probes to the common output terminal of the resistor.
What does a resistor do on a cooling fan?
The cooling fan resistor is meant to send power to the fans in steps , so that the fans may operate at different speeds. If any of the individual steps or switches fail, it will disable the cooling fans from operating on that speed setting.
How do you test a blower motor with a multimeter?
Using a multimeter set on the Ohm scale, use the positive lead and test the black wire. To check the purple wire for current, use your ignition key and turn it to the run setting, turn the heater power to full power and set the multimeter to DC power. If your meter reads “no current” the motor is no good.
