2013 F150 Heater Blower Stop After Few Minutes Then Starts Again for a Few Seconds
Blower motor, resistor: how it works, symptoms, issues, testing
Updated: August 01, 2021
The motor that runs the fan in the heating and air conditioning system in a car is chosen a blower motor. It's located inside the dash, oftentimes on the contrary 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.
What is the divergence? A blower motor resistor is a simple electric resistor. It's used in cars where the blower motor has merely 4 or v fixed speeds, every bit on the left side in this diagram. Run into the photo of the Ford blower motor resistor.
Cars with an automated climate control system and vehicles where the blower speed can be adapted gradually are equipped with an electronic blower motor control module, meet the photo.
In most modern cars, the blower motor resistor or the command module are installed inside i of the ducts in the HVAC system, close to the blower motor. This is done, so the resistor or a control module is cooled downwards by passing air. In some older cars, a blower motor resistor was installed on the firewall with access from under the hood.
Blower motor resistor / control module bug
Problems with a blower motor resistor are common in many cars. The virtually common symptom of a failed blower motor resistor is when the heater fan only runs at the highest speed setting (4 or 5) and doesn't work at low speeds. In some cars, a failed blower motor resistor can cause a heater fan to finish working completely.
In most cases, a blower motor resistor fails due to corrosion or overheating. Sometimes, the mechanical resistance to the motor rotation causes an excessive electric current that can overheat and prematurely impairment the blower motor resistor. For example, this happens when the fan blade is jammed by a foreign object or when the motor bearings are worn out and it doesn't spin freely.
Problems with a blower motor control module are less frequent, just it fails for the same reason: due 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 (due east.yard., older GM trucks), a failed blower control module or processor can cause the blower motor to go on 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 vary. Frequently a visual inspection of the resistor reveals the problem. For example, as yous can see in this photo, the blower motor resistor in this Ford Escape has failed due to corrosion.
If the resistor shows no visual damage, the resistance between terminals must be checked and compared to specifications. If the resistance is out of specs, the resistor must be replaced.
For example, in this photograph we measured the resistance of this blower motor resistor. Co-ordinate to the service manual, it must be around 4-5 ohms.
Failed resistor tested with an ohm-meter
In our case the ohmmeter shows open excursion, which means the resistor has failed.
Sometimes, a blower motor resistor might fail due to problems with the blower motor itself. This ways after replacing the blower motor resistor, cheque 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 resistor to neglect again. For example, this issue was mutual in older Chrysler and Dodge minivans. In this case, the blower motor must likewise exist replaced. 1 of the symptoms of a worn out blower motor is that information technology can intermittently produce a loud screeching noise when running.
How to test the blower motor?
If the blower motor doesn't piece of work at all, the blower motor itself must be tested first. Typically it's done past measuring the voltage at the blower motor connector when information technology's turned on. If in that location is a voltage at the motor (at least 4-6 Volt at low speed and 12 Volt at high speed), just the motor doesn't run, the motor is bad or jammed.
Testing the voltage at the blower motor. If there is a voltage at the motor (at least four-6 Volt at low speed and 12 Volt at loftier speed), but the motor doesn't run, the motor is bad.
Things like leaves, twigs, nuts, pieces of a ripped motel filter can jam the blade of the blower motor. This happens often in many cars.
If there is no voltage at the motor, the entire blower motor circuit must be tested, starting from a fuse. See: how to check a fuse in a car.
If a blower motor is bad, it will need to be replaced. The blower motor replacement costs from $320 to $650, depending on the car. In many cars it'due south fairly piece of cake; the blower motor is located backside the glove box and held by three-four screws. In others it might be located inside the dash (east.yard. Mazda five) which makes replacement difficult.
If you need a proper diagnostic process, we accept posted several links where you tin access a service manual for your car for a subscription fee. Check this mail service, scroll downward the folio.
How is the blower motor control module tested?
Mechanics at a dealership can diagnose the HVAC arrangement with a scan tool. If the scan tool is not available, in many cars with an automatic climate control system at that place is a cocky-testing or diagnostic mode.
Typically it can exist activated by pressing and holding unlike buttons. For case, in the 2009 Honda Accord, the service transmission describes the process as follows: Turn the ignition to ON. Press and hold the OFF button and within 10 seconds press and release the Window Defogger button five times. The system enters the self-diagnostic mode and at the terminate of it, if at that place is a problem, the error code will be displayed on the brandish. The service manual describes the testing procedure for each code. Run across, for instance, these YouTube videos; add brand and model of your vehicle.
Another way is to cheque the voltage at the blower motor, the blower motor command module and other parts of the circuit co-ordinate to the service transmission. For example, in the mentioned 2009 Honda Accord, the + 12V power is supplied directly to the blower motor through the fuse and then through the relay.
Testing Honda power transistor (blower motor control module).
The blower motor control module (Honda calls it Ability Transistor) supplies the ground. The power transistor has iv wires: two come up from the climate control organisation control unit, one is the ground, ane goes to the negative terminal of the blower motor. The service transmission advises measuring the voltage at the blower motor, and then if non OK, at the power transistor and and so on.
A failed power transistor was a fairly common cause for not working blower motor in some Honda and Acura vehicles. For instance, the Honda bulletin 03-048 described a problem where the blower motor for the rear HVAC organisation in the 2003 Airplane pilot would not work at all speeds.
Honda blower motor control module (ability transistor)
The bulletin recommends replacing the rear ability transistor as a solution.
BMW calls the blower motor command module a Last Stage Unit, which is too fairly common to neglect. Sometimes it doesn't neglect completely, but causes the blower motor to stop working intermittently or run at various speeds. See these YouTube videos for more than info.
In some GM trucks, a blower motor command module failure can cause the front blower motor to end working or run afterwards the vehicle has been shut off. The GM bulletin 06-01-39-002C describes this problem that happens in cold weather. The message advises replacing the blower motor control module. GM calls it Linear Ability Module (LPM). Lookout man these YouTube videos for more than info.
Repair options
Your local mechanic or whatever modest repair shop should be able to diagnose the problem. Of class, the quickest mode is to make an appointment with your dealer. Many dealers have the office in stock. The blower motor resistor or command module replacement is non very expensive.
For example, ane of our colleagues had a problem with his 2011 Ford Escape: the fan merely worked at the speed 4. He paid $50 to diagnose and $112 to supercede the resistor at a local Ford dealership. When the aforementioned problem occurred two years later, he ordered the part online for $25 and replaced it himself.
In the 2008-2011 Ford Escape / Mazda Tribute, the blower motor resistor is located on top of the HVAC unit, behind the glove box.
In the 2008-2011 Ford Escape, the resistor is located behind the glove box on top of the HVAC unit air duct. Information technology's held by 2 screws and is like shooting fish in a barrel to supervene upon. See the photograph.
In the 2008-2011 Ford F150, the blower motor resistor is as well located backside the glove box, but is installed on the right side of the plastic air duct. This thread at f150online.com shows where the resistor is located.
The writer of this blog shared his experience of replacing the blower motor resistor in Jeep Liberty. In some older cars and trucks, the blower motor resistor is installed on the firewall, with access from under the hood.
How the blower motor resistor works
Typical blower resistor diagram
This diagram shows how the blower motor resistor is connected in a typical car. In this automobile, in the highest "4" fan speed 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 resistor is bad.
In this diagram, the fan switch is set up to the speed "i", so the blower motor current is reduced by three resistors (R2 + R3 + R4) connected in series. The electric current flow is shown in blue and red.
In the setting "2", there are two resistors connected in series, and in "3", at that place is but one resistor.
Adding resistance to the electrical circuit reduces the current in the circuit. When several resistors are connected in series, the total resistance increases and is equal to the sum of individual resistances.
Source: https://www.samarins.com/glossary/blower-motor-resistor.html
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