How does a blower motor resistor control the fan speed?

The blower motor resistor controls the fan speed of the blower motor and the resulting change in air pressure produced by the movement of the blower fan. It accomplishes this by regulating the electric current that powers the motor.

How to replace the blower motor resistor on a Chevy Silverado?

In this video we show you how to replace the blower motor resistor in a Chevy Silverado, Also it is very important to consider the blower motor anytime a resistor fails. A worn out blower motor may still work, however it will require more amperage to operate, this extra amperage is pulled through the resistor and can easily burn it out. Loading…

What are the symptoms of a failed blower motor resistor?

Blower motor resistor problems. Problems with a blower motor resistor are common in many cars. The most common symptom of a failed blower motor resistor is when the heater fan only runs at high speed and doesn’t work at low speeds.

Can a broken motor switch stop a blower?

A broken blower motor switch can also stop the blower from changing to certain speed settings. If your blower motor cannot change to certain speeds, check both the resistor and the switch on your dashboard. The most common failure points are the resistor and the motor itself.

Where is the AC blower motor resistor harness located?

If you can no longer adjust the air speed with your AC controls or your AC system no longer blows chances are you need a new Blower Motor Resistor. This COMPLETE KIT includes the Blower Motor Resistor and New Wire Harness. The AC Blower Motor Resistor is located on lower passenger side dash and is easily accessible by removing a few screws.

How can I Fix my blower motor resistor?

Purchase an upgraded pigtail and splice it into the harness along with a new blower motor resistor. Conduct an amperage draw test at the same time to rule out excessive current draw from the blower motor. Car makers design their HVAC systems to reduce the possibility of debris getting into the system.

How do you troubleshoot a blower motor resistor?

This can be annoying, but troubleshooting is easy. If you start at the blower motor, and check resistance in the circuit, you will find the problem in no time. Power supplied from the fuse panel passes through the switch to the blower resistor assembly.

What are the symptoms of a bad heater motor resistor?

Symptoms of a Bad or Failing Heater Blower Motor Resistor. 1 1. Blower motor stuck on one speed. A common symptom of a faulty blower motor resistor is a blower motor that is stuck on one setting. The blower 2 2. Blower motor does not work on certain settings. 3 3. No air from the vehicle’s vents.

How is the speed of the blower motor controlled?

On climate control systems without automatic temperature controls, the blower motor speeds are controlled by a switch wired to a stepped resistor that usually includes a thermal fuse.

What does the resistor on a heater do?

It is responsible for controlling the blower motor’s fan speed. When fan speed is changed via the knob on the instrument cluster, the blower motor resistor changes setting, which changes the speed of the blower motor.

How does a relay work on a blower motor?

Finally, with the fan switch on the highest speed, the fan motor is receiving system voltage (14.5 with the engine running). Some systems will energize a relay when the switch is set at the highest fan speed. The relay then closes its contacts, feeding full voltage to the fan, because a relay can handle the current better than the fan switch.

How does the resistor on a blower motor work?

The blower motor resistor allows you to change the speed of the fan and the flow of air. The blower motor connector joins the two and sends a signal from the blower motor resistor to control the speed of the blower motor.

How do you plug in a Ford Motorcraft blower motor resistor?

The plug fit perfectly and securely into the new ford motorcraft blower motor resistor. I suggest using a dab of dielectric grease on the each terminal of the connector and the edges of the connector before inserting it into the resistor socket.

Why do you need a blower motor connector?

The blower motor connector links the blower motor to the blower motor resistor. The blower motor is part of your vehicle’s air conditioning and heating system that pushes air through your vehicle’s vents. Without it, there would be no circulation of air. The blower motor resistor allows you to change the speed of the fan and the flow of air.

What is the name of the Denso fan blower motor resistor?

The label on the outside of the part reads, “Denso 077800-0111, 12V”. One fact that may help someone diagnose the problem is the fact that when the part is unplugged you get Lo and Hi speeds. The good news is that the part only takes about 15 mins to remove and install.

Where does the power transistor go in a blower motor?

The power transistor has 4 wires: two come from the climate control system control unit, one is the ground, one goes to the negative terminal of the blower motor. The service manual advises measuring the voltage at the blower motor, then if not OK, at the power transistor and so on.

How much does it cost to replace a blower motor resistor?

The blower motor resistor or control module replacement is not very expensive. For example, one of our colleagues had a problem with his 2011 Ford Escape: the fan only worked at the speed 4. He paid $50 to diagnose and $112 to replace the resistor at a local Ford dealership.

Where is the blower motor resistor located on a car?

It’s located inside the dash, often on the opposite side of the steering wheel or inside the engine compartment on the firewall. A blower motor resistor or a blower motor control module is the part that controls the speed of the blower motor.

The electronic module that controls the speed of the blower motor is called a blower motor control module. In some cars, the blower motor has only 4 or 5 fixed speeds. In this case, the speed of the blower motor is controlled by a blower motor resistor.

What causes a blower motor to stop working?

If your blower motor has stopped working, check the connector. If it’s in bad shape, or has melted, it may be the cause of the motor’s failure. Get your blower motor working with a connector from O’Reilly Auto Parts. Check out our blower motor resistor connector options for your vehicle.

What happens when a cooling fan resistor fails?

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. You may notice that the cooling fans only operate at one speed, when they used to operate on two or more. 3.

Why is the resistor not working on my blower?

Hi There, The resistor is what controls the speed of the blower motor, not the relay. The blower motor relay supplies power to this motor when you turn the switch to “on” that can sometimes fail. When this happens, you may notice that you will not feel anything blowing out of the vents at all.

How is a step resistor used in a fan?

A voltmeter connected to both ends of a resistor while current is passing through it to a load will measure the amount of voltage being “dropped” by the resistor. Because lower voltage means lower current delivered to the fan, the stepped resistor circuit can be used to control fan speed.

What happens if the blower motor only works on high speed?

In other designs, the failure of 1 resistor means you lose only one speed. However, most car makers bypass the blower motor resistor completely when you move the fan speed switch to high. If your blower only operates on its highest speed, chances are you have the series type of blower motor resistor. This is the most common failure mode.

How much does a blower motor resistor cost?

Depending on the manufacturer and model, a blower motor resistor can go anywhere between $3 and $335 on CarParts.com. The replacement parts come in individual units, sets of two resistors, or as part of a blower motor resistor kit.

What happens when a blower motor resistor fails?

The blower motor resistor is the component directly responsible for controlling the blower motor fan speed. If the resistor shorts or fails, it may cause the blower motor to remain stuck on one fan speed.

Why does my blower fan only work on one speed?

by Lee Sallings. The most common symptom of a faulty blower motor resistor is a blower fan that only works on one speed, usually high. This can be annoying, but troubleshooting is easy. If you start at the blower motor, and check resistance in the circuit, you will find the problem in no time.

How does a 3 speed blower motor work?

Older style blower motor resistor with exposed resistor elements. The blower motor resistor is what’s responsible for giving you three blower speeds. The resistor block contains three different high resistance coils. Think of these coils like a filament in a light bulb.

What to do if your blower motor only works on high speed?

If your blower only operates on its highest speed, chances are you have the series type of blower motor resistor. This is the most common failure mode. To repair the problem, simply replace the resistor block. It’s usually located in the ductwork (to keep the coils cool) below the glove box.

Why is the fan on my Nissan Frontier not working?

Disconnected the motor and brought it into the garage. The fan has a big white fan blade on top and the motor sits in a black plastic case. One philips screw holds the motor in the casing. I carefully pried the motor out of the casing. My fan blade was a bugger to get off. Seized on.

What makes a fan blower motor not work?

There was no rust in mine. A lot of dark black brush residue, couple pieces of what appeared to be small leaves, and dirt. The fan motor parts themselves were very clean after I knocked on the concrete floor to knock the debris out. I think the lube and cleaning made the difference.

Where is the fan motor on my truck?

So I pulled my fan motor (Located by the passengers foot, under the glove box). To get at all 3 mounting screws I had to remove a side panel which was connected with clips and just pulled off by hand. Removed the motor but left it connected to the truck. It was a nice day so the motor was working. Man that thing is powerful

How does the resistor work on a blower motor?

Your vehicle’s blower motor resistor controls the speed of your blower motor. When you turn a knob to produce more air flow for heat or cool air, the resistor adjusts the electrical resistance to control the power sent to your blower motor. Since the blower motor and resistor are working almost constantly, it can wear out over time.

Where is the blower motor resistor located on a Ford Escape?

In the 2008-2011 Ford Escape, the resistor is located behind the glove box on top of the HVAC unit air duct. It’s held by two screws and is easy to replace. See the photo. In the 2008-2011 Ford F150 the blower motor resistor is also located behind the glove box, but is installed in the right side of the plastic air duct.

What to do if your blower resistor Burns?

Look for obvious signs of corrosion and burns from overheating. If you see signs of overheated connectors, replace the blower resistor and its connector, but again, you must splice the wires right, or you’ll have problems at the splice later on.

Why does my blower motor only work at slow speed?

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.

Where do I replace the resistor on my blower motor?

To repair the problem, simply replace the resistor block. It’s usually located in the ductwork (to keep the coils cool) below the glove box. Unplug the electrical connector, remove the screws and replace the unit. Replacement blower motor resistor blocks are usually available from any auto parts store or the dealer.

Is the speed of the blower controlled by the resistor?

The blower speed can be adjusted in almost every modern car. Some cars have blowers that have 4 to 5 fixed speed settings that can be selected, but in this case, the speed of the blower motor is controlled by a blower motor resistor. 1. No air blowing through vehicle’s vents

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