A car blower motor is a crucial part of its heating and cooling systems. While problems with the blower motor might not have an effect on the vehicle’s operation, you may have difficulties taking control over the temperature of your vehicle’s interior, thus having an effect on your comfort level. It, therefore, helps to quickly identify the early signs of a failing blower motor and replace or fix the faulty component as soon as possible.
The following is a troubleshooting and how-to guide for common car blower motor issues.
What are the symptoms of a bad blower motor?
If you notice any of the following signs, it could be an indication that your blower motor is bad:
Weak airflow from the vents
As your blower motor wears with time, it may reach a time it will not be able to push as much air through your vehicle’s HVAC system. If you start to notice that the power of the blowers is not as powerful as they once were, this is could indicate the blower motor is bad.
Fan only blows at certain speeds
If you notice that the fan only works at certain speeds, but not others, it could be a sign the blower motor is bad. Most blower motors are designed to operate at different speeds so as to able to regulate different cabin temperatures efficiently. If the blower motor is faulty, it can fail to push air at any of its designed settings.
No air flow from the vents
If there is no air flow from the vents when the heater or air conditioning is activated it could be another symptom that the blower motor is bad. A faulty blower motor can disable an otherwise fully functional vehicle HVAC system, thus making the driving experience less comfortable for the passengers.
Unusual noises
Unusual noises coming from your vehicle’s HVAC system is another indicator of an issue with the blower motor. Foreign objects can get sucked into the engine compartment and get caught in the blower motor fan. The fan blades can as a result get damaged or even snap off, and when that happens, you will notice a slapping or sudden pop noise that comes from right behind the vent.
You might also hear whirring noises or noises that get louder when you increase the fan speed. All these are signs of problems with the blower motor.
Smoke or burn smells
Smoke or burning smells in your car while driving can indicate a bad blower motor, but can also be due to other causes. If the blower motor is burned out, there could be a burning smell or you may see smoke.
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Can blower motor make a humming sound?
A mild humming sound is normal. That’s the blower-moving air. This hum changes intensity as you change air flow settings. Your car blower motor can make a loud humming sound when turned on because of a number of issues. It is not uncommon for these blowers to loosen their fan balance over time. Also, there could be some debris inside the fins.
To troubleshoot the problem, find the blower motor in your vehicle and check all the screws holding it to the HVAC system to make sure they are all tight. You can also turn on the blower motor and then apply pressure on the backside of it to hear if that changes the humming noise.
If thereafter you tore the motor out and there are no foreign objects stuck inside, the screws are tight, and pushing on the backside changes the noise then you may need to replace the blower.
Car blower motor works intermittently
If the car blower motor works intermittently this is likely caused by worn brushes inside the motor. Once the motor starts running, normal vibration keeps the brushes working. The problem worsens will worsen over time. One way to establish if this is the issue is the motor will often start running when you bang on the heater box.
If the fan usually starts up right away, then quits after a few minutes, the cause is likely to be overheated and burned connector terminals, usually on the control panel or speed switch. Replacing only the control panel will not fix the problem entirely. You also need to cut out and replace the mating connector terminals individually, otherwise, the resistance they cause will generate more heat, and that heat will also overheat the new controller terminals.
Car blower motor speeds up and slows down by itself
When a car blower motor speeds up and slows down by itself, this is likely a sign the motor is starting to fail and so it ends up slowing down when it has to work hard on hot days. If something in the motor has broken down, such as an electrical connection, has bad wiring, or some other operational issue, the fan won’t turn.
Another possible cause is a bad relay or capacitor. A capacitor that is malfunctioning or failing can cause the motor to slow down/or overheat. In this case, you might need to replace the capacitor.
Fan belts can become stretched, cracked, and break during normal wear and tear. This can result in a slow-turning fan.
Car blower motor won’t turn off
The most common reason that your blower motor won’t turn off is because of a stuck relay keeping the circuit closed. Relays help open and close electrical circuits to turn components, like a fan, on and off. Over time, relays can fail or stick together from electrical currents, causing a circuit to stay closed and constantly supply power.
How to straight wire a car blower motor
There are usually only two wires coming out of most blower motors. All you have to do is run a wire straight from the battery to one of them and the other one to the ground. It usually doesn’t matter which one of the two wires you use since they are not hot/ground specific. Use proper gauge wires so they don’t heat up and fail prematurely.
Here are wiring instructions you can try:
- Run a wire from the positive battery terminal
- Route the wire through the firewall at the passenger side
- Go to the dash and pull the blank farthest to the right. Install a switch.
- Unplug the stock plug from the blower motor and run another wire from the switch to the blower.
- Make a jumper that goes from the motor to the stock plug. This feeds ground back to the dash, the fan switch and on to ground. The female connector goes in the motor and the male blade goes to the right side of the plug.
- Install a relay near the battery and wire it to an ignition wire so it automatically cuts off with the car key.
Check the current rating of the motor. 30 amp relay and 10 gauge wire will work for the power circuit and 14-gauge and 16-gauge wire for the switching circuit.
When the blower motor does not work at any speed, the most likely causes are the following:
- Blown power supply fuse
- Bad motor ground connection
- Bad motor speed control module
- Failed motor
How long does it take to replace a blower motor in a car?
It takes an experienced technician around 4 hours to replace a car blower motor. For a DIY enthusiast at home, with decent skills, it can take about 5 hours or more.
Troubleshooting Car Blower Motor
Follow these instructions to troubleshoot problems with your car’s blower motor:
- If the blower only works on high speed, this is a dead ringer symptom of a bad blower resistor, not a bad speed switch. Replace the resistor.
- If the blower works on slow speeds but not on high speed, check for a bad fuse or bad high-speed relay. Swap the high-speed relay with another relay with the same part number. Also, check the fuse for the control side of the high-speed replay. Make sure the ground side of the high speed relay is working.
- If the blower works on some speeds but not others this can be a bad blower motor resistor or a failed speed switch. Refer to your vehicle’s wiring diagram and check for continuity on all resistors and speed switch settings.
- If the blower motor resistor has repeat failures check for full airflow at the vents. If the airflow is restricted or lower than normal, check cabin air filter. If it is okay, check for debris on the evaporator or heater. Decreased airflow causes the blower motor resistor to overheat and fail.
- If the blower motor fuse blows repeatedly blower s drawing too much power. Check the cabin air filter for clogging. Check for airflow restrictions in the duct, paying attention to debris on the evaporator or heater core.
- If the blower motor doesn’t work in cold weather there is a bad bearing in the blower motor. Replace the blower motor.
- If the blower motor doesn’t shut off, if you have a variable speed blower motor, replace the blower motor speed control module. If you have a three or four speed blow motor, remove the blower motor relay. If the motor stops, replace the relay.
How to Test a Blower Motor
If you hear that the blower motor is operating but don’t feel any air flowing through the vents, the problem is with the airflow controls. If the blower motor is not running, follow these troubleshooting instructions:
- Use a voltmeter or ohmmeter to check for a blown fuse. If there is one, replace it.
- Start the car and see of the blower works. If the fuse blows again, check for loose circuits.
- If the circuits are okay but the blower motor keeps blowing fuses, replace the blower motor.
If your car engine is working fine but the blower isn’t, you can test the blower motor to see if it needs cleaning or repair. Here is what to do:
- Disconnect the car battery.
- Detach the blower motor from its connector.
- Unscrew all the screws on the blower motor and place them in a container or somewhere you can easily replace them.
- Locate the retainer clip in the center of the blower wheel. Disconnect it from the motor shaft and set it aside.
- Clean out any debris from the motor.
- Use a cleaner for electrical parts to clean the blower motor.
- Oil the bearings.
- Check that the blower wheel spins freely and all the other parts are operating properly. If there is a part that is not working properly, clean and oil it, and test it again.
How to Troubleshoot and Fix Grinding Car AC Noises
Loud noises you hear when your car’s heater or AC is on often indicate a blower motor issue. To troubleshoot and fix the problem, follow these steps:
- First, test your blower motor. With the key on, turn on your AC or heater. Does the bad blower motor sound get worse when you crank your blower motor all the way up?
- Next, locate the blower motor. Blower motors are usually located under the glove box, but it may depend on your vehicle.
- After you locate the blower motor, remove it and check for any debris that may be caught inside it. If you find a foreign object wedged inside it, gently remove it.
- Reinsert and retest the blower motor. If you don’t hear anything even after putting it on full blast, then you know the debris was what was causing the noise. If you still have a noisy car AC, you likely need to replace your blower motor.
How to Replace a Car Blower Motor
Note: The location and mode of installation vary from car to car. Be sure to consult your user manual or a car model specific guide for extra tips
Before setting out to change your car’s blower motor, make sure you have to do what is required as far as safety is concerned. Park on a flat surface with the parking brake on, pop the hood, and disconnect the battery.
Then proceed with the steps below to replace the blower motor:
- Locate the blower motor. You can find the blower-motor location in the repair manual. It is usually in the passenger-side footwell area, below the glove box.
- Remove the lower trim panel below the glove box.
- Open and remove the glove box (optional on some vehicles) by pushing retaining clips aside to unlatch the glove box from the housing.
- Going headfirst into the footwell with a flashlight, look up until you locate the blower motor.
- Locate the 3-6 bolts holding it in place and remove using sockets and ratchet.
- Then, slide the blower motor assembly out and slip off the HVAC vent connections. Finally, remove the electrical power connector by hand or by carefully using a small screwdriver on the clips.
- Compare the old blower motor to your new part and orient the replacement blower motor in a similar way as it was installed. There may be a gasket to replace as well.
- Plugin the power connection, and slide HVAC vents on. Slide the blower motor into its bracket and bolt down.
- Replace the glove box and lower trim panel. Reconnect the battery.
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To ensure everything is working properly, turn on the engine and test operation by selecting different levels of heat and air conditioning. Make sure there is proper airflow with no unusual noises.