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How do I test a blower motor resistor?

Author of the blog (work in a car repair shop)
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How do I 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.How to Test A Blower Motor Resistor? Locate the blower motor resistors fuse. The first thing you need to do is determine where the blower motor resistor fuse is located in your vehicle. Test the blower motor resistor fuse. Once the blower motor resistor fuse is located, the next step is to test if it's working properly. ... Take out the blower motor resistor and test it. Following the same steps mentioned earlier, make sure to unplug the blower motor and connected it to the 12 Volt test ... Test the blower motor ground. Blower Motors rely on certain grounds connected to the vehicle's body, and sometimes a bad blower motor can happen due to a problem with the ...

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.

How do you test a blower motor with a multimeter?

Turn off your vehicle, set your multimeter to Ohms, and check for resistance between the blower's positive and negative terminals. You may also turn the car key to run without starting the engine, put the cooling system at full blast, and check for DC voltage. If none of these produces a reading, the blower is bad.

How much resistance should a blower motor resistor have?

According to the service manual, it must be around 4-5 ohms. In our case the ohmmeter shows open circuit, which means the resistor has failed. Sometimes, a blower motor resistor might fail due to problems with the blower motor itself.

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 will a bad blower motor resistor do?

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 many volts should a blower motor receive?

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.

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.

Is there a fuse for the heater blower?

Many vehicles have two fuses for the blower motor, one in the interior fuse block and the other under the hood. The blower motor is usually under the dashboard on the passenger side.

Is there a fuse for blower motor?

What does a bad blower motor sound like?

A defective blower motor will make a continuous sound noticeable by the passengers in the vehicle. It can manifest as a knocking, whirring, clunking, vibrating, squealing, or whining noise that persists until the blower motor is replaced.

How do you know if a resistor is bad?

A good resistor should test within its rated range. A bad resistor will either show infinite resistance or a measurement far higher than its rated resistance. In either case the resistor is no longer functioning properly.

Can a bad blower motor cause no heat?

Problems with Your Blower Motor or Blower Motor Resistor Without it, there's no circulation of air—hot, cold, or otherwise. The blower motor resistor is the part that controls the fan speed of the blower motor. Both of these components can fail, resulting in the heating system simply not working.

What happens if 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.

How do you diagnose a bad blower motor switch?

Another symptom of a bad or failing blower motor switch is a switch that is stuck, or frequently gets stuck. If the switch or any of its contacts becomes damaged, this may cause the switch to jam, or get stuck when you trying to change the setting.

What should the amps be on a blower motor?

How do I test a resistor with a multimeter?

How do I know if a resistor is burnt?

Connect resistor to multimeter and measure voltage drop across the burnt resistor. Now measure the current flowing into the resistor. Multiply both values and you will get the wattage of Resistor (As P = VI i.e. Ohm's law). This wattage must be less than the wattage of the resistor being replaced.

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.

Why does my blower resistor go out?

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.

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.

Where is the blower motor relay fuse located?

Under the instrument panel, look under the glove box. On the right side of the fender wall you will find another fuse box. The blower motor fuse is easy to replace.

What relay controls the blower motor?

In a blower motor, the relay supplies the power that allows the fans to circulate warmed air. Essentially an on/off switch, the blower motor relay's reactions start and end the heating process in HVAC systems by controlling the flow of current between the power source and the motor.

Where is the blower motor relay fuse located?

Under the instrument panel, look under the glove box. On the right side of the fender wall you will find another fuse box. The blower motor fuse is easy to replace.

What causes blower motor failure?

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.

How to test a blower motor resistor fuse?

Test the blower motor resistor fuse Once the blower motor resistor fuse is located, the next step is to test if it's working properly. To do so, use a 12 Volt test light and connect it from one side to the ground and the other side to the fuse terminal. Monitor the behavior of the power on the terminals and see if the fuse is working properly.

How do I know if my blower resistor is bad?

Look for obvious signs of corrosion and burns from overheating. 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 is a blower motor power transistor?

The blower motor power transistor is commonly referred to as the blower motor resistor when in the true technical sense it isn't a resistor. This is due to the fact that the blower motor power transistor does pretty much the exact same job as the old style resistors of vehicles of the 80 and 90's. What job?... Vary the blower motor fan speed.

How does a blower resistor work?

To understand how the blower resistor works, a simple electrical principle called “ voltage drop ” is used. When a switch, a resistor, and a load are wired in series, the resistor “drops” some of the voltage passing through it, effectively reducing both current flow and voltage at the motor.

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