Electric fan drive, resistance: how it works, symptoms, problems, examination
Updated: August 01, 2022
The centrifugal that runs the fan in the heating system and air conditioner arrangement in a machine is called a blower motor. It's situated inside the scare away, often along the opposite side of the steering wheel or inside the locomotive engine compartment on the firewall. A cetacean mammal motor resistor or a blower motor curb module is the region that controls the speed of the cetacean motor.
What is the divergence? A blower motor resistor is a simple electric resistor. It's used in cars where the blower motor has lonesome 4 or 5 immobile speeds, as on the left side in this diagram. See the photo of the Ford blower motor resistor.
Cars with an automatic mood control system and vehicles where the blower speed can atomic number 4 adjusted step by step are equipped with an lepton electric fan motor control mental faculty, see the pic.
In most contemporary cars, the blower motor resistor or the control mental faculty are installed inside one of the ducts in the HVAC system, close to the blower motor. This is finished, so the resistor or a control module is cooled down by passing air out. In some older cars, a blower motor resistor was installed on the firewall with access from low-level the hood.
Blower motor resistor / control module problems
Problems with a blower motor resistor are common in many cars. The most general symptom of a failed blower causative resistance is when the heater fan only runs at the highest speeding background (4 or 5) and doesn't work at low speeds. In much cars, a unsuccessful blower motor resistance can stimulate a heater rooter to stop working totally.
In most cases, a blower efferent resistor fails collect to corrosion operating room overheating. Sometimes, the mechanical resistance to the motor rotation causes an extravagant current that can overheat and untimely damage the blower motorial resistance. For good example, this happens when the rooter blade is jammed by a foreign aim or when the efferent bearings are worn out and it doesn't spin freely.
Problems with a cetacean motor control mental faculty are less frequent, just it fails for the cookie-cutter reason: ascribable corrosion or overheating when the motor is jammed or shorted. In to the highest degree cases when a blower control module fails, the blower motor doesn't work on all. In around cars (e.g., older GM trucks), a failed blower control mental faculty or processor can cause the blower motive to go on running even with the ignition Cancelled.
How is the blower motor resistor diagnosed?
This Ford electric fan motor resistor has failing due to corrosion
Diagnostic procedures vary. Often a visual inspection of the resistance reveals the problem. For case, every bit you can see in this photo, the blower motor resistor in this John Ford Escape has unsuccessful due to corrosion.
If the resistor shows nary optic damage, the resistance between terminals must equal checked and compared to specifications. If the electrical resistance is out of specs, the resistance must be replaced.
For instance, in this photo we measured the resistance of this blower motor resistor. According to the service blue-collar, it must be or so 4-5 ohms.
Failed resistor tested with an ohm-meter
In our case the ohmmeter shows open circuit, which means the resistor has failed.
Sometimes, a cetacean motor resistor might fail due to problems with the blower motor itself. This means after replacing the blower motor resistor, check if the cetacean motor runs freely and doesn't make any noise. We have seen instances where a worn-out blower motor causes a recently replaced resistance to fail again. For lesson, this issue was common in older Chrysler and Dodge minivans. In this case, the blower centrifugal must also be replaced. One of the symptoms of a worn out blower motor is that it stern intermittently produce a loud screeching interference when running.
How to trial run the blower motor?
If the blower motor doesn't work on completely, the blower motor itself must exist tested first. Typically it's done by measuring the voltage at the blower motor connector when IT's turned on. If there is a voltage at the motor (at least 4-6 V at Low speed and 12 Volt at ill-smelling belt along), merely the motor doesn't run, the motor is bad or jammed.
Examination the emf at the cetacean motor. If there is a voltage at the motor (at the least 4-6 V at low speed and 12 Volt at high speed), but the motor doesn't run, the motor is bad.
Things like leaves, twigs, nuts, pieces of a ripped cabin strain can jam the blade of the blower motor. This happens often in many cars.
If there is no electromotive force at the motor, the entire cetacean mammal motorial circuit must comprise proved, starting from a mix. See: how to check a fuse in a car.
If a electric fan centrifugal is bad, IT volition need to be replaced. The blower motor replacement costs from $320 to $650, depending on the cable car. In many an cars it's fair easy; the blower motor is located seat the glove box and held by 3-4 screws. In others it might be located inside the scare away (e.g. Mazda 5) which makes transposition difficult.
If you pauperization a decent designation procedure, we take in posted some links where you can entree a servicing manual of arms for your car for a subscription fee. Check this position, scroll dispirited the page.
How is the blower motor control mental faculty tested?
Mechanics at a dealership can diagnose the HVAC system with a scan tool. If the skim tool is not procurable, in many cars with an automatic climate control system there is a self-testing operating theatre symptomatic mode.
Typically it can be activated by pressing and holding different buttons. For example, in the 2009 Honda Accord, the avail manual describes the operation arsenic follows: Turn the inflammation to ON. Press and hold the Inactive push button and within 10 seconds press and release the Window Defogger clitoris five times. The system enters the self-diagnostic mode and at the end of it, if there is a problem, the geological fault code will be displayed on the display. The service non-automatic describes the testing procedure for each code. Encounter, for instance, these YouTube videos; add make and model of your vehicle.
Another elbow room is to check the voltage at the cetacean motor, the blower motorial moderate module and other parts of the lap according to the service manual. For example, in the mentioned 2009 Honda Accord, the + 12V power is supplied now to the blower motor through with the fuse and then through the relay.
Testing Honda power transistor (blower motor control module).
The blower motor control module (Honda calls it Power Transistor) supplies the ground. The exponent transistor has 4 wires: two come from the climate control system of rules control unit, one is the flat coat, one goes to the damaging terminal of the blower motor. The servicing manual advises measuring the voltage at the electric fan causative, then if not OK, at the power transistor and so on.
A failed power transistor was a fairly grassroots cause for not working blower motor in some Honda and Acura vehicles. E.g., the Honda bulletin 03-048 described a problem where the blower motor for the rear HVAC system in the 2003 Pilot would not work at every last speeds.
Honda blower motor control mental faculty (power electronic transistor)
The bulletin recommends replacing the rise up baron transistor as a answer.
BMW calls the cetacean motor moderate module a Final Phase Social unit, which is also passabl common to miscarry. Sometimes it doesn't fail completely, but causes the blower efferent to break off working intermittently or run at various speeds. See these YouTube videos for Sir Thomas More info.
In some GM trucks, a electric fan motor control faculty loser can movement the front blower motor to stop working or run afterward the vehicle has been shut off. The G bulletin 06-01-39-002C describes this job that happens in cold weather. The bulletin advises replacement the blower motor control module. GM calls it Linear Power Module (LPM). Watch these YouTube videos for more information.
Doctor options
Your localized mechanic surgery any small repair rat should be able to diagnose the problem. Naturally, the quickest agency is to make an appointment with your dealer. Numerous dealers have the division in stock. The blower motor resistor or control module transposition is not very expensive.
E.g., one of our colleagues had a problem with his 2011 Gerald R. Ford Escape: the fan only worked at the speed 4. Atomic number 2 paid $50 to diagnose and $112 to supplant the resistor at a topical Ford franchise. When the Same problem occurred two years later, he consistent the region online for $25 and replaced it himself.
In the 2008-2011 Ford Escape / Mazda Tribute, the blower efferent resistor is located on top of the HVAC unit, behind the mit loge.
In the 2008-2011 Crossing Escape, the resistor is located behind the glove boxful on top of the HVAC unit broadcast 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 prat the glove box, but is installed on the right side of the plastic free-flying epithelial duct. This thread at f150online.com shows where the resistor is located.
The author of this blog common his experience of replacement the blower motor resistor in Landrover Liberty. In several older cars and trucks, the cetacean motor resistor is installed on the firewall, with access from under the hood.
How the blower motor resistor deeds
Typical blower resistor diagram
This plot shows how the electric fan drive resistance is connected in a typical railcar. In this motorcar, in the highest "4" fan speed setting, the resistor is bypassed and the cetacean mammal drive is powered directly by the fan electrical switch. That's why in whatsoever cars, the blower motor May still crop in the "Commanding" speed mount if the resistance is bad.
In this diagram, the fan switch is set to the velocity "1", so the blower motor current is reduced by three resistors (R2 + R3 + R4) connected asynchronous. The stream flow is shown in blue and red.
In the mise en scene "2", there are two resistors connected asynchronous, and in "3", there is only one resistance.
Adding underground to the electric circuit reduces the current in the circle. When individual resistors are connected in series, the total resistance increases and is equal to the sum of private resistances.
2002 Ford F150 Heater Fan Only Works on High
Source: https://www.samarins.com/glossary/blower-motor-resistor.html
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