The blower motor is the component that runs the fan in the air conditioning system in a car. The fan pushes heated or cooled air through dashboard vents depending on the climate system settings and the fan speed selected.
The motor is located inside the dash, usually on the opposite side of the steering wheel or inside the engine compartment on the firewall. A blower motor control or a blower motor resistor module is the part that controls the speed of the blower motor.
In most modern cars, the automatic climate control system is often equipped with an electronic blower motor control module that is installed inside one of the ducts in the HVAC system, close to the blower motor.
But how do you hotwire a blower motor? Adjusting the fan speed will send a signal through a resistor to the blower motor to either pick up the pace or slow it down.
However, if the fan doesn’t work, it’s important to check fuses to make sure that they’re still functional, before actually pointing the finger to the motor blower.
How To Hotwire a Blower Motor
In most blower motors, there are usually two wires coming out. All you have to do is run a wire straight from the battery to one of them and the other one to the ground. You might want to use a toggle switch so you can turn it off.
It usually doesn’t matter which one of the two wires is hot or ground-specific, but it’s best to use a wire that has some copper strands to prevent it from heating up and failing prematurely.
Wiring the blower directly from the battery should work just fine. You may, however, need to consider disconnecting the wire from the servo or whatever normally controls the blower and fuse the connection to the battery at about 20 Amps or so.
Also, if you want to get fancy, opt for an SPDT switch so that you can toggle the blower between normal and direct-to-battery.
Blower Motor Module/Resistor Problems
When a blower motor fails, only a small amount of air will be delivered through the interior vents based on the amount of outside air entering the air conditioning system. Problems with a blower motor resistor are common in many vehicles.
The most common sign of a failed blower motor module is when the heater fan runs at the highest speed setting of 4-5 and doesn’t work at low speeds. In some cars, a faulty blower motor resistor can cause the heater to stop functioning completely.
Oftentimes, a blower motor resistor fails due to overheating or corrosion. The mechanical resistance to the motor rotation may cause an excessive electric current that can overheat and prematurely damage the blower motor resistor.
For instance, this can occur when the fan blade is jammed by a foreign object or when the motor bearings are worn out, keeping from spinning freely.
How to Test a Blower Motor
If the blower motor isn’t working, then the blower motor itself should be tested first. This is usually done by measuring the voltage at the blower motor connector when it is turned on.
To test a blower motor, use an ohmmeter or voltmeter to check for a blown fuse. In case you find one, replace it then start the car to see if the blower motor works.
If there is a voltage motor of at least 4-6 Volt at low speed, and 12 Volt at high speed, but the motor doesn’t operate, then the motor is faulty or jammed.
Objects like twigs, nuts, leaves, and pieces of a ripped cabin filter can jam the blade of the blower motor. If the motor has no voltage, then the entire blower motor circuit should be tested, starting from the fuse.
However, if the circuits are in proper repair, but the blower motor keeps blowing fuses, consider replacing the blower motor. The blower motor replacement costs from $320 to $650, based on the car.
It is relatively easy in most cars as the blower motor is located behind the glove box and secured by 3-4 screws. In others, the blower motor might be located inside the dash, which makes the replacement a bit complex.
How To Lubricate a Blower Motor
If the blower motor has oil parts, then it should be lubricated at least once per year. To each port, apply two or three drops of 10-weight non-detergent motor oil (not all-purpose oil). Be careful not to over-lubricate.
If the blower shaft has oil parts, it should be lubricated annually as well, following the same procedure.
How Do You Determine if It’s the Blower Motor or Resistor Bad?
One common symptom of a faulty blower motor resistor is when the blower motor is stuck on a one-speed setting. In such a case, the heating and air conditioning system may still function at the speed, but the resistor will need to be replaced in order to achieve full functionality.
The Typical Cost for Heater Blower Motor Replacement
In most cases, this repair is on the relatively budget side. For instance, a new blower may run between $150 and $100. Most blower motors sit in the dash underneath the glove box and are rather accessible for replacement. The installation cost will run in the range of $80-$100.
Meanwhile, if you want to replace the heater motor, the price for a new one will run around $40-$50. Keep in mind that pricing tends to vary depending on your location and your vehicle make and model.