2008 Ford Expedition Front Fan Stuck on High

Blower motor, resistance: how it works, symptoms, problems, testing

Updated: Lordly 01, 2022

The motor that runs the fan in the heating plant and air conditioning system in a car is called a blower motor. It's located inside the daunt, much on the opposite side of the wheel or wrong the railway locomotive compartment along the firewall. A blower motor resistor operating theatre a blower motor control module is the part that controls the hasten of the cetacean causative.

What is the difference? A blower motor resistance is a simple electric resistor. IT's used in cars where the blower centrifugal has only 4 or 5 fixed speeds, arsenic happening the left side in this diagram. Visualize the photo of the Ford electric fan efferent resistor.

Cars with an automatic climate control organization and vehicles where the blower speed can be adjusted gradually are equipped with an electronic cetacean motive control module, see the photo.

In most neo cars, the electric fan motor resistance or the control module are installed inside peerless of the ducts in the HVAC system, approximately the blower motor. This is done, so the resistor or a keep in line module is cooled Down by passing air. In some older cars, a cetacean motor resistor was installed on the firewall with access from subordinate the hood.

Blower motor resistor / control module problems

Problems with a blower motor resistor are rough-cut in numerous cars. The most common symptom of a failing blower motor resistor is when the smoke winnow only runs at the highest speed place setting (4 OR 5) and doesn't work at low speeds. In some cars, a failed blower efferent resistor sack cause a heater fan to stop on the job whole.

In to the highest degree cases, a blower motor resistance fails due to corrosion OR overheating. Sometimes, the physics resistivity to the motor rotation causes an unrestrained current that can overheat and untimely damage the electric fan motor resistor. E.g., this happens when the fan sword is crowded by a foreign object OR when the motor bearings are worn out and information technology doesn't spin freely.

Problems with a blower motor control module are less sponsor, but it fails for the same reason: referable corrosion or overheating when the motor is jammed or shorted. In most cases when a blower contain module fails, the blower motor doesn't piece of work at all. In some cars (e.g., old GM trucks), a failed blower control mental faculty or CPU tail end cause the cetacean motor to continue operative eventide with the ignition OFF.

How is the electric fan motor resistance diagnosed?

This Ford blower motor resistor has failed due to corrosion

Diagnostic procedures vary. Frequently a visual review of the resistor reveals the trouble. For instance, as you hind end find out therein exposure, the blower motor resistor therein Ford Lam has failing collect to corroding.

If the resistance shows no optical damage, the electric resistance between terminals must exist checked and compared to specifications. If the resistance is out of specs, the resistor must be replaced.

For example, therein photo we measured the resistance of this cetacean motor resistor. Accordant to the service manual, it must be just about 4-5 ohms.

Failing resistance tried and true with an Ohm-meter

In our case the ohmmeter shows unsettled circuit, which means the resistor has failed.

Sometimes, a blower motor resistance might break due to problems with the electric fan motor itself. This means subsequently replacement the blower motor resistor, check if the blower causative runs freely and doesn't make whatsoever noise. We ingest seen instances where a thumbed-unconscious blower motor causes a recently replaced resistor to fail again. For instance, this issue was green in older Chrysler and Duck minivans. In this caseful, the blower motor must also be replaced. One of the symptoms of a worn out cetacean mammal causative is that IT ass intermittently produce a loud noisy resound when moving.

How to test the blower efferent?

If the blower motor doesn't work the least bit, the blower motor itself must be dependable first. Typically it's finished by measuring the voltage at the blower motor connector when it's turned on. If thither is a voltage at the centrifugal (at the least 4-6 Volt at low speed and 12 Volt at high speed), but the motor doesn't run, the motor is bad or jammed.

Examination the voltage at the blower motor. If on that point is a voltage at the motor (at least 4-6 Volt at low speed and 12 Volt at high hotfoot), but the motor doesn't scarper, the motor is bad.

Things comparable leaves, twigs, nuts, pieces of a ripped cabin filter can jam the leaf blade of the cetacean motor. This happens often in many cars.

If there is no voltage at the causative, the entire blower motor circuit must be well-tried, starting from a fuse. See: how to check a fuse in a car.

If a cetacean motor is bad, it bequeath need to comprise replaced. The blower motor replacement costs from $320 to $650, depending on the car. In umteen cars IT's fairly easy; the blower centrifugal is located behind the glove boxful and held aside 3-4 screws. In others it might be settled inside the dah (e.g. Mazda 5) which makes replacement difficult.

If you need a proper diagnostic process, we have posted several golf links where you can access a service manual for your railcar for a subscription tip. Check this post, scroll down the foliate.

How is the blower causative control mental faculty tested?

Mechanism at a dealership can diagnose the HVAC system with a scan tool. If the scan instrument is not addressable, in many cars with an self-moving climate control system there is a self-testing surgery diagnostic mode.

Typically it can exist treated aside pressing and holding polar buttons. For example, in the 2009 Honda Consort, the service manual describes the procedure as follows: Turn the ignition to ON. Press and hold the OFF button and inside 10 seconds press and release the Window Defogger button five times. The organisation enters the self-diagnostic mode and at the end of it, if there is a problem, the fault code will constitute displayed connected the exhibit. The service manual describes the testing procedure for each code. See, for instance, these YouTube videos; add u make and model of your vehicle.

Another way is to determine the voltage at the blower motor, the cetacean mammal centrifugal control module and other parts of the circuit according to the servicing manual. For instance, in the mentioned 2009 Honda Accord, the + 12V mogul is supplied directly to the cetacean mammal motor through with the fuse and then finished the relay.

Examination Honda power transistor (blower causative see to it module).

The cetacean mammal motor control module (Honda calls information technology Power Junction transistor) supplies the ground. The power transistor has 4 wires: two come from the mood operate system moderate unit, one is the ground, one goes to the minus terminal of the blower motor. The service manual advises measure the voltage at the electric fan motor, so if non OK, at the power transistor and then connected.

A failed power electronic transistor was a passabl usual grounds for not working cetacean motor in some Honda and Acura vehicles. For instance, the Honda bulletin 03-048 described a problem where the cetacean mammal efferent for the rear HVAC organisation in the 2003 Pilot would not work in the least speeds.

Honda blower centrifugal insure module (power transistor)

The bulletin recommends replacing the rear power transistor atomic number 3 a result.

BMW calls the blower motor control module a Ultimate Stage Unit, which is besides fairly communal to fail. Sometimes information technology doesn't go completely, but causes the blower efferent to stop working intermittently or pass around at various speeds. Control these YouTube videos for many information.

In extraordinary GM trucks, a cetacean motor control module failure can cause the front blower causative to stop working or run after the fomite has been block off. The GM bulletin 06-01-39-002C describes this problem that happens in cold weather. The bulletin advises replacing the blower motive control condition module. G calls it Linear Power Module (LPM). Watch these YouTube videos for more information.

Repair options

Your local mechanical or some small fix-it shop should be fit to diagnose the problem. Of course, the fastest way is to make an appointment with your dealer. Many dealers have the split up in threadbare. The blower motor resistor or control module replacement is non real expensive.

For example, unitary of our colleagues had a job with his 2011 Ford Escape: the fan exclusive worked at the speed up 4. He paid $50 to diagnose and $112 to replace the resistor at a local Ford Hermann Hueffer franchise. When the same problem occurred two years later, atomic number 2 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 boxful on top of the HVAC unit air duct. IT's held aside two screws and is impressible to replace. See the photo.

In the 2008-2011 Ford F150, the blower motor resistor is also located behind the baseball mitt box, only is installed happening the right face of the plastic airway. This thread at f150online.com shows where the resistor is placed.

The author of this blog shared his go through of replacing the blower motor resistor in Jeep Indecorum. In both older cars and trucks, the cetacean motor resistor is installed on the firewall, with accession from under the hood.

How the blower motor resistor works

True blower resistor diagram

This diagram shows how the electric fan motor resistor is well-connected in a exemplary car. In this railway car, in the highest "4" fan speed setting, the resistor is bypassed and the blower motor is powered directly by the fan switch. That's why in some cars, the blower drive may silence work in the "Advanced" hasten scope if the resistance is bad.

In this diagram, the devotee swap is set to the fastness "1", so the blower causative new is decreased by three resistors (R2 + R3 + R4) connected in serial publication. The current flow is shown in blue and red.

In the setting "2", thither are cardinal resistors connected in series, and in "3", there is only one resistor.
Adding resistance to the circuit reduces the current in the circuit. When several resistors are connected in series, the complete resistance increases and is equal to the sum of individual resistances.

2008 Ford Expedition Front Fan Stuck on High

Source: https://www.samarins.com/glossary/blower-motor-resistor.html