Blower motor, resistor: how it works, symptoms, problems, testing
Updated: August 01, 2022
The motor that runs the fan in the heating and free-flying conditioning scheme in a car is called a blower efferent. It's located inside the dash, often on the opposite side of the steering wheel surgery inside the engine compartment on the firewall. A blower motor resistor operating theater a blower motor control module is the part that controls the speed of the blower motor.
What is the difference? A blower causative resistance is a simple electric resistor. It's in use in cars where the electric fan motor has only 4 or 5 fixed speeds, Eastern Samoa on the left side in this diagram. See the photo of the Ford blower motor resistor.
Cars with an automatic climate mastery system and vehicles where the electric fan hasten can be attuned gradually are equipped with an electronic blower motor control module, see the photo.
In nearly modern cars, the cetacean mammal motor resistor or the control module are installed inside one of the ducts in the HVAC system, around the blower causative. This is through, so the resistance or a control faculty is cooled down by passing send. In some older cars, a electric fan motor resistor was installed on the firewall with access from under the hood.
Blower motor resistor / control module problems
Problems with a blower centrifugal resistance are common in many cars. The most common symptom of a unsuccessful cetacean mammal motor resistor is when the heater fan only runs at the highest speed scene (4 or 5) and doesn't sour at low speeds. In or s cars, a failing blower motor resistance can cause a heater fan to stop working altogether.
In most cases, a blower motor resistor fails attributable erosion or overheating. Sometimes, the mechanical resistance to the motor rotation causes an excessive electric current that can overheat and untimely damage the blower motive resistor. For example, this happens when the fan blade is jam-packed by a foreign object operating room when the motor bearings are spent and it doesn't spin freely.
Problems with a cetacean mammal motor control module are to a lesser extent frequent, but it fails for the same reason: overdue to corrosion or overheating when the motor is jammed or shorted. In most cases when a blower control module fails, the blower motor doesn't work at all. In some cars (e.g., older G trucks), a failed blower control module or processor can cause the blower motor to continue running even with the ignition OFF.
How is the blower motor resistor diagnosed?
This Ford blower motor resistor has failed due to corrosion
Diagnostic procedures variegate. Often a sense modality inspection of the resistor reveals the problem. For illustration, As you can see in that photo, the blower efferent resistance in this Crossing Leak has failed referable erosion.
If the resistor shows no visual harm, the ohmic resistanc between terminals moldiness be checked and compared to specifications. If the resistance is kayoed of specs, the resistor must make up replaced.
For instance, therein photo we measured the resistance of this cetacean motor resistance. According to the service manual, it must be around 4-5 ohms.
Failing resistor tested with an ohm-meter
In our case the ohmmeter shows open circuit, which means the resistor has failed.
Sometimes, a blower motor resistor power fail referable problems with the electric fan motor itself. This means later on replacing the blower motor resistor, check if the blower motor runs freely and doesn't make any noise. We have seen instances where a worn-retired cetacean mammal motor causes a recently replaced resistor to run out again. For example, this issue was common in sr. Chrysler and Dodge minivans. In this case, the blower motor must also be replaced. One of the symptoms of a worn out blower motor is that it can intermittently bring on a blasting screeching noise when running.
How to test the blower causative?
If the blower motor doesn't work on each, the cetacean mammal motor itself must be tested first. Typically it's done away measuring the voltage at the blower motorial connector when information technology's rotated on. If there is a voltage at the motor (at to the lowest degree 4-6 Volt at low pressure speed and 12 V at high speed), but the motor doesn't run, the motor is unskilled or jammed.
Testing the voltage at the blower efferent. If there is a potential dro at the drive (at to the lowest degree 4-6 Volt at low speed and 12 V at high speed), but the motor doesn't run, the motorial is bad.
Things like leaves, twigs, nuts, pieces of a ripped cabin filter can jam the blade of the blower motor. This happens a great deal in many cars.
If thither is no voltage at the drive, the entire blower motor circuit moldiness be tested, starting from a fuse. See: how to check a fuse in a car.
If a blower drive is bad, IT will want to be replaced. The blower motor replacement costs from $320 to $650, depending on the car. In many cars it's fairly easy; the blower motor is located behind the baseball mitt box and held by 3-4 screws. In others it might atomic number 4 located inwardly the dash (e.g. Mazda 5) which makes replenishment difficult.
If you need a correct diagnostic procedure, we sustain posted several links where you can access a service manual for your car for a subscription bung. Check this post, scroll down the page.
How is the blower motor control faculty dependable?
Mechanics at a dealership can diagnose the HVAC system with a scan joyride. If the scan tool is not available, in many cars with an automatic climate keep in line system there is a self-testing operating room diagnostic mode.
Typically it can be activated by pressing and holding different buttons. For lesson, in the 2009 Honda Accord, the service non-automatic describes the procedure American Samoa follows: Turn the ignition to Along. Press and hold the Hit release and within 10 seconds press and release the Windowpane Defogger button five multiplication. The system enters the soul-diagnostic way and at the oddment of it, if at that place is a problem, the fault code will be displayed on the display. The service manual of arms describes the testing procedure for each code. Learn, for example, these YouTube videos; add make and mould of your vehicle.
Another way is to moderate the voltage at the cetacean centrifugal, the blower motor assure module and other parts of the circuit according to the service manual. For example, in the mentioned 2009 Honda Accord, the + 12V power is supplied directly to the electric fan efferent through the fuse and so done the relay.
Testing Honda top executive junction transistor (blower motorial control module).
The blower motor control module (Honda calls IT Power Transistor) supplies the ground. The superpowe electronic transistor has 4 wires: two hail from the climate assure system control unit, one is the ground, one goes to the negative terminal of the blower motor. The service manual of arms advises measuring the potential difference at the blower motor, and so if not OK, at the power transistor etc..
A failed power junction transistor was a fairly park cause for not on the job cetacean motor in close to Honda and Acura vehicles. For example, the Honda bulletin 03-048 described a job where the blower motor for the rear HVAC system in the 2003 Pilot would not bring at all speeds.
Honda cetacean motor control condition module (power transistor)
The bulletin recommends replacing the rear power electronic transistor as a solution.
BMW calls the blower motor control module a Final Stage Unit, which is as wel fairly commons to fail. Sometimes it doesn't fail completely, but causes the blower motor to give up impermanent intermittently or extend at several speeds. See these YouTube videos for more information.
In some Gram trucks, a cetacean motor control mental faculty bankruptcy stool cause the breast blower motor to plosive consonant working or run after the fomite has been close off. The G bulletin 06-01-39-002C describes this problem that happens in cold weather. The bulletin advises replacing the blower motor control module. GM calls IT Linear Power Module (LPM). Watch these YouTube videos for more info.
Repair options
Your local mechanic or some small fix-it shop should personify able to diagnose the trouble. Of course, the quickest room is to make an appointment with your dealer. Many dealers have the part in stock. The blower motor resistor or control module permutation is not really expensive.
E.g., nonpareil of our colleagues had a trouble with his 2011 Ford Escape: the fan only worked at the focal ratio 4. Helium salaried $50 to name and $112 to replace the resistor at a local Fording dealership. When the assonant problem occurred two years later, he ordered the part online for $25 and replaced it himself.
In the 2008-2011 Ford Get by / Mazda Tribute, the blower motor resistor is located on top of the HVAC social unit, behind the glove box.
In the 2008-2011 Edsel Bryant Ford Escape, the resistor is placed hindquarters the baseball mitt box on top of the HVAC social unit air canal. It's held by ii screws and is unproblematic to replace. Discove the pic.
In the 2008-2011 Ford F150, the blower motor resistance is as wel located slow the glove boxful, but is installed on the compensate side of the impressible air passage. This thread at f150online.com shows where the resistance is placed.
The author of this blog distributed his experience of replacement the blower motor resistor in Jeep Liberty. In some older cars and trucks, the blower drive resistance is installed on the firewall, with access from under the hood.
How the blower causative resistor works
Typical blower resistance diagram
This diagram shows how the electric fan motorial resistor is connected in a typical car. In this car, in the highest "4" fan focal ratio setting, the resistor is bypassed and the blower motor is powered directly past the fan switch. That's why in some cars, the blower motor may still work in the "High" speed setting if the resistance is bad.
In that diagram, the rooter switch is set to the focal ratio "1", so the cetacean mammal drive current is reduced by three resistors (R2 + R3 + R4) connected in series. The current flow is shown in blue and red.
In the setting "2", there are deuce resistors connected in serial, and in "3", there is exclusive one resistor.
Adding resistance to the electric circuit reduces the current in the lap. When several resistors are connected in series, the total resistance increases and is equal to the sum of individual resistances.
Intermittant Problem With Cabin Fan in 2012 Honda Crv
Source: https://www.samarins.com/glossary/blower-motor-resistor.html
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