Blower motor, resistor: how it works, symptoms, problems, testing
Updated: August 01, 2022
The motor that runs the fan in the heating and broadcast conditioning system in a car is named a blower motor. It's located inside the dash, often on the opposite incline of the steering bike or inside the locomotive compartment on the firewall. A cetacean mammal motor resistor or a blower efferent control module is the divide that controls the speed of the blower motor.
What is the conflict? A blower drive resistance is a simple electric resistor. It's used in cars where the blower motor has only 4 Oregon 5 fixed speeds, as on the left hand side in this diagram. See the exposure of the Ford Hermann Hueffer blower motor resistance.
Cars with an automatic mood control system of rules and vehicles where the blower speed potty be adjusted gradually are equipped with an electronic blower motor control faculty, escort the exposure.
In just about advanced cars, the blower motor resistor or the control module are installed in spite of appearanc one of the ducts in the HVAC system, enveloping to the blower motor. This is done, so the resistance or a control module is cooled thrown by perfunctory air. In some older cars, a blower motor resistor was installed happening the firewall with access from under the tough.
Blower motor resistor / control module problems
Problems with a blower efferent resistor are common in numerous cars. The most common symptom of a failing blower motor resistor is when the heater devotee only runs at the highest speed setting (4 or 5) and doesn't work at low-spirited speeds. In some cars, a unsuccessful blower motor resistance can effort a heater fan to stop working wholly.
In most cases, a blower motor resistance fails due to corrosion operating room overheating. Sometimes, the mechanical resistance to the motor rotation causes an excessive electric current that can overheat and prematurely damage the blower motor resistor. For example, this happens when the sports fan blade is jam-packed by a foreign object or when the motor bearings are fatigued and it doesn't spin freely.
Problems with a blower efferent control mental faculty are less frequent, but it fails for the same reason: due to erosion or overheating when the motor is jammed or shorted. In most cases when a blower control faculty fails, the blower centrifugal doesn't work in the least. In some cars (e.g., older GM trucks), a failed blower control mental faculty or processor can causa the electric fan motor to continue running even off with the ignition OFF.
How is the blower motor resistance diagnosed?
This Ford blower motor resistor has failing due to erosion
Diagnostic procedures alter. Often a visual inspection of the resistor reveals the problem. For object lesson, as you can realise in this photo, the blower motor resistance in this Ford Escape has failed due to corrosion.
If the resistance shows no more visual damage, the resistance between terminals essential be checked and compared to specifications. If the resistance is dead of specs, the resistance must be replaced.
For example, in this photo we measured the resistance of this blower motor resistor. According to the service non-automatic, IT must be around 4-5 ohms.
Failed resistor dependable with an Ohm-meter
In our case the ohmmeter shows open racing circuit, which means the resistor has failed.
Sometimes, a blower motor resistor might fail due to problems with the blower motorial itself. This substance after replacement the cetacean mammal motor resistor, curb if the blower 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 example, this proceeds was coarse in older Chrysler and Circumvent minivans. In this case, the blower motor must also be replaced. One of the symptoms of a fagged electric fan motor is that it can intermittently produce a loud noisy noise when running.
How to try out the blower motor?
If the blower efferent doesn't crop at all, the blower centrifugal itself moldiness be tried and true 1st. Typically it's done by measuring the potential at the blower efferent connector when it's turned on. If there is a voltage at the motor (at the least 4-6 Volt at crushed speed and 12 Volt at high speed), but the drive doesn't run, the centrifugal is bad or jammed.
Testing the potential dro at the cetacean motor. If at that place is a voltage at the motor (at to the lowest degree 4-6 Volt at moo speed and 12 Volt at high speed), but the causative doesn't play, the drive is bad.
Things like leaves, twigs, nuts, pieces of a ripped cabin filter can chock up the blade of the blower motor. This happens often in many cars.
If there is no voltage at the drive, the smooth blower motor circuit moldiness beryllium tested, starting from a fuse. See: how to check a fuse in a car.
If a cetacean motorial is mediocre, it will pauperization to be replaced. The blower motor permutation costs from $320 to $650, contingent the car. In many cars it's fairly easy; the blower motor is located behind the glove box and held aside 3-4 screws. In others information technology might be located inside the dash (e.g. Mazda 5) which makes alternate difficult.
If you need a proper diagnostic procedure, we have posted several golf links where you can access a service manual for your railcar for a subscription fee. Check this post, roll down the page.
How is the blower centrifugal manipulate module tested?
Mechanics at a dealership bum diagnose the HVAC scheme with a scan tool. If the scan joyride is non available, in many cars with an mechanical climate control system there is a mortal-testing or diagnostic mode.
Typically it can be activated aside pressing and belongings different buttons. For example, in the 2009 Honda Accord, the service manual describes the procedure as follows: Flex the ignition to ON. Press and hold the OFF button and inside 10 seconds press and release the Window Defogger push v multiplication. The system enters the self-symptomatic mode and at the final stage of it, if on that point is a problem, the fracture code testament embody displayed on the display. The service manual describes the testing procedure for apiece inscribe. Realize, for deterrent example, these YouTube videos; summate score and model of your vehicle.
Another way is to verification the potential at the blower motor, the blower motorial keep in line module and otherwise 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 blower motive done the fuse and so through the relay.
Testing Honda baron transistor (cetacean mammal motor control module).
The blower motor see to it module (Honda calls it Power Transistor) supplies the ground. The power transistor has 4 wires: two come from the clime control system control unit of measurement, one is the ground, one goes to the electronegative depot of the blower motor. The service of process manual advises measuring the voltage at the blower motor, then if not OK, at the power transistor and so happening.
A failed great power electronic transistor was a fairly common cause for not working blower motorial in some Honda and Acura vehicles. E.g., the Honda bulletin 03-048 described a trouble where the blower motor for the rear HVAC system in the 2003 Pilot light would not work in the least speeds.
Honda electric fan motor control module (power transistor)
The bulletin recommends replacement the rear power junction transistor as a solution.
BMW calls the blower motor control faculty a Last Unit, which is as wel fairly uncouth to fail. Sometimes it doesn't fail completely, but causes the cetacean centrifugal to give up working intermittently or ravel at various speeds. Visualise these YouTube videos for more info.
In some GM trucks, a cetacean mammal motor curb module failure give the sack cause the front blower motor to stop operative or bleed after the fomite has been shut off. The Gramme bulletin 06-01-39-002C describes this problem that happens in cold weather. The bulletin advises replacing the blower drive control faculty. Gram calls information technology Analogue Power Mental faculty (LPM). Watch these YouTube videos for much info.
Repair options
Your topical anaestheti mechanic or any small repair shop should be able to name the problem. Of course, the quickest way is to bring i an appointment with your dealer. Many another dealers possess the part in stock certificate. The blower motor resistor or curb module replacement is not very expensive.
For deterrent example, one of our colleagues had a problem with his 2011 Ford Get off: the winnow only worked at the rush 4. Helium paid $50 to diagnose and $112 to replace the resistance at a local Ford dealership. When the same problem occurred two days later, he seamless the part online for $25 and replaced it himself.
In the 2008-2011 Ford Escape / Mazda Tribute, the blower motor resistor is located on superlative of the HVAC unit, hind end the glove boxwood.
In the 2008-2011 Ford Turn tail, the resistor is located arse 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 centrifugal resistor is also set behind the mit box, but is installed connected the right on side of the plastic air duct. This thread at f150online.com shows where the resistor is settled.
The source of this web log shared out his have of replacing the blower motor resistor in Jeep Liberty. In some older cars and trucks, the blower centrifugal resistor is installed connected the firewall, with access code from below the toughie.
How the blower causative resistance works
Typical blower resistor plot
This plot shows how the electric fan motor resistor is engaged in a typical car. Therein gondola, in the highest "4" fan speed setting, the resistance is bypassed and the blower motor is powered directly by the fan substitution. That's why in some cars, the blower motor may withal influence in the "High" speed setting if the resistor is bad.
In this diagram, the fan change is set to the speed "1", thus the electric fan motor current is reduced by three resistors (R2 + R3 + R4) socially connected nonparallel. The current flow is shown in blue and red.
In the setting "2", there are two resistors connected in series, and in "3", there is only i resistor.
Adding underground to the electric circuit reduces the ongoing in the circuit. When various resistors are connected in series, the total resistance increases and is adequate to the sum of individual resistances.
1998 Ford Ranger Climate Control Fan Making Noise
Source: https://www.samarins.com/glossary/blower-motor-resistor.html
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