The motor the runs the pan in the heating and also air conditioning system in a car is referred to as a blower motor. It"s located inside the dash, frequently on the opposite side of the steering wheel or within the engine compartment ~ above the firewall. A blower engine resistor or a blower motor regulate module is the component that controls the rate of the blower motor.


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how the speed of the blower engine is controlled. Check out also: photograph of a Mazda blower engine resistor Honda blower motor regulate module.
What is the difference? A blower motor resistor is a basic electric resistor. It"s offered in cars whereby the blower motor has only 4 or 5 fixed speeds, together on the left side in this diagram. View the photo of the Ford blower motor resistor. Cars v an automatic climate manage system and also vehicles where the blower speed have the right to be changed gradually are equipped with an digital blower motor control module, view the photo. In most contemporary cars, the blower motor resistor or the regulate module are set up inside one of the ducts in the HVAC system, close come the blower motor. This is done, for this reason the resistor or a control module is cooled down by pass air. In some older cars, a blower motor resistor was set up on the firewall with accessibility from under the hood.

Blower engine resistor / control module problems

troubles with a blower motor resistor are usual in countless cars. The most common symptom that a failed blower motor resistor is as soon as the heater fan only runs in ~ the highest possible speed setup (4 or 5) and doesn"t work-related at short speeds. In some cars, a failed blower engine resistor can reason a heater pan to protect against working completely. In most cases, a blower motor resistor fails as result of corrosion or overheating. Sometimes, the mechanical resistance come the motor rotation reasons an extreme electric existing that have the right to overheat and prematurely damages the blower engine resistor. Because that example, this happens once the pan blade is jammed through a international object or when the engine bearings are worn out and it doesn"t spin freely. troubles with a blower motor manage module are less frequent, yet it fails for the very same reason: as result of corrosion or overheating when the motor is jammed or shorted. In most instances when a blower regulate module fails, the blower motor doesn"t work at all. In some cars (e.g., enlarge GM trucks), a failed blower regulate module or processor can cause the blower engine to proceed running also with the ignition OFF.

How is the blower engine resistor diagnosed?


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This Ford blower engine resistor has actually failed as result of corrosion
Diagnostic actions vary. Regularly a visual inspection of the resistor reveals the problem. Because that example, as you have the right to see in this photo, the blower motor resistor in this Ford Escape has failed due to corrosion. If the resistor mirrors no visual damage, the resistance in between terminals need to be checked and compared come specifications. If the resistance is the end of specs, the resistor should be replaced. for example, in this picture we measured the resistance the this blower engine resistor. According to the business manual, it must be around 4-5 ohms.
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failed resistor tested through an ohm-meter
In our instance the ohmmeter shows open circuit, which method the resistor has failed. Sometimes, a blower engine resistor might fail due to problems with the blower engine itself. This means after replacing the blower engine resistor, inspect if the blower motor runs freely and doesn"t make any type of noise. We have seen instances whereby a worn-out blower motor reasons a newly replaced resistor come fail again. Because that example, this problem was common in enlarge Chrysler and Dodge minivans. In this case, the blower motor must additionally be replaced. Among the symptoms of a worn out blower engine is the it have the right to intermittently develop a according to screeching noise once running.

How to check the blower motor?

If the blower motor doesn"t job-related at all, the blower engine itself should be experiment first. Frequently it"s excellent by measure up the voltage at the blower engine connector as soon as it"s turned on. If there is a voltage in ~ the engine (at the very least 4-6 Volt at short speed and 12 Volt at high speed), however the motor doesn"t run, the engine is negative or jammed.
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trial and error the voltage in ~ the blower motor. If over there is a voltage at the engine (at least 4-6 Volt at low speed and 12 Volt at high speed), but the motor doesn"t run, the engine is bad.
Things prefer leaves, twigs, nuts, piece of a ripped cabin filter deserve to jam the blade of the blower motor. This happens often in numerous cars. If there is no voltage in ~ the motor, the whole blower engine circuit should be tested, beginning from a fuse. See: exactly how to check a fuse in a car. If a blower motor is bad, that will must be replaced. The blower motor replacement expenses from $320 to $650, depending upon the car. In countless cars it"s reasonably easy; the blower engine is situated behind the gloves box and held by 3-4 screws. In others it can be situated inside the dash (e.g. Mazda 5) which makes replacement difficult. If you need a suitable diagnostic procedure, we have actually posted several web links where girlfriend can accessibility a service manual for your auto for a subscription fee. Examine this post, scroll under the page.

How is the blower motor control module tested?

Mechanics in ~ a dealership have the right to diagnose the HVAC mechanism with a scan tool. If the scan device is not available, in countless cars through an automatically climate control system there is a self-testing or diagnostic mode.
frequently it deserve to be activated by pressing and also holding different buttons. For example, in the 2009 Honda Accord, the company manual defines the procedure together follows: turn the ignition come ON. Press and also hold the turn off button and also within 10 seconds press and release the window Defogger button five times. The system enters the self-diagnostic mode and at the finish of it, if over there is a problem, the error code will certainly be displayed on the display. The service manual describes the experimentation procedure because that each code. See, because that example, these YouTube videos; add make and also model of her vehicle. Another means is to inspect the voltage at the blower motor, the blower motor manage module and also other components of the circuit according to the company manual. Because that example, in the pointed out 2009 Honda Accord, the + 12V power is supplied straight to the blower motor v the fuse and then v the relay.
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testing Honda strength transistor (blower motor manage module).
The blower motor regulate module (Honda call it strength Transistor) gives the ground. The strength transistor has 4 wires: 2 come from the climate control system regulate unit, one is the ground, one goes to the negative terminal that the blower motor. The company manual advises measure up the voltage in ~ the blower motor, climate if not OK, in ~ the strength transistor and also so on. A failed strength transistor was a fairly common reason for not functioning blower engine in some Honda and also Acura vehicles. For example, the Honda bulletin 03-048 defined a problem where the blower motor for the rear HVAC mechanism in the 2003 Pilot would not job-related at every speeds.
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Honda blower motor manage module (power transistor)

Repair options

Your neighborhood mechanic or any tiny repair shop should have the ability to diagnose the problem. That course, the quickest way is to do an appointment with your dealer. Many dealers have the part in stock. The blower motor resistor or manage module instead of is not an extremely expensive. for example, one of our colleagues had actually a problem with his 2011 Ford Escape: the fan only worked at the speed 4. He payment $50 come diagnose and also $112 to replace the resistor in ~ a local Ford dealership. When the same problem emerged two year later, the ordered the component online for $25 and replaced the himself.
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In the 2008-2011 Ford escape / Mazda Tribute, the blower motor resistor is situated on top of the HVAC unit, behind the glove box.
In the 2008-2011 Ford Escape, the resistor is located behind the gloves box on peak of the HVAC unit wait duct. It"s hosted by two screws and also is straightforward to replace. View the photo. In the 2008-2011 Ford F150, the blower motor resistor is likewise located behind the gloves box, however is mounted on the best side of the plastic wait duct. This thread in ~ f150online.com reflects where the resistor is located. The writer of this blog mutual his suffer of replacing the blower engine resistor in Jeep Liberty. In some older cars and trucks, the blower motor resistor is set up on the firewall, with accessibility from under the hood.

How the blower engine resistor works


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common blower resistor diagram


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This diagram shows just how the blower motor resistor is linked in a usual car. In this car, in the highest "4" fan rate setting, the resistor is bypassed and also the blower motor is powered straight by the fan switch. That"s why in part cars, the blower motor may still occupational in the "High" speed setup if the resistor is bad. In this diagram, the fan switch is collection to the rate "1", therefore the blower motor present is decreased by three resistors (R2 + R3 + R4) linked in series. The current flow is presented in blue and red. In the setting "2", there space two resistors linked in series, and in "3", over there is only one resistor. Including resistance come the electric circuit reduce the present in the circuit. When several resistors are connected in series, the total resistance increases and also is same to the sum of separation, personal, instance resistances.