Rattling Noise Coming From Air Vent Car – What Could Be Wrong?

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Do you hear a rattling noise coming from the air vent car in your car? It sounds like something is loose inside the air vent, and you wonder what the problem could be and how to resolve it. We’ve researched this topic and have the answer here for you.

A rattling noise coming from the air vent is usually caused by foreign objects and small debris in the blower motor. It can also be caused by a damaged blower motor cage. In addition, the rattling noise can be the result of a loose blower motor. 

A rattling noise coming from your car's air vent is very common. In this post, we will talk about causes and solutions for this annoying sound, so read on!

Car air conditioning. The air flow inside the car. Detail interior of car - Rattling Noise Coming From Air Vent Car - What Could Be Wrong

What Is A Blower Motor?

A blower motor is an electric motor used to move air through a ventilating fan. It is part of the A/C system.

The purpose of a blower motor is to move air through the vents in your car. It is controlled by an electric switch or dial that opens and closes the blower motor.

This allows the blower motor to run at different speeds and provide different amounts of airflow. The blower motor is usually found at the bottom of the dashboard, on the passenger side behind the glove compartment.

How To Diagnose A Rattling Noise From A Car Air Vent

Car air conditioning. The air flow inside the car. Detail interior of car

This rattling noise usually occurs when a broken cage on the blower motor is making contact with something inside. There is also the possibility of the blower motor accumulating dirt or debris that causes it to rattle when the blower motor is running. 

In this case, you might want to check the blower motor by removing it and observing its physical condition. Here are the steps to follow to diagnose a rattling noise in a blower motor:

1. Check if the blower motor is mounted properly

One of the reasons why your blower motor might be rattling is because it is not mounted properly. To check if the blower motor is mounted properly, try to jiggle it back and forth to check if it's loose.

You may have to replace the blower motor if it's already loosened. Additionally, the blower motor might be touching or hitting something else. If this happens, the blower motor probably has a damaged cage.

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2. Inspect the blower motor's spline shaft

When you think of spline shafts, the first thing that comes to mind is probably the spline in your car's steering system.

This is a set of cylindrical teeth (grooves) that engage a mating set of teeth (grooves) on the shaft to transmit rotational motion.

Check the spline shaft for any visible cracks or damage. Make sure the spline shaft is tight and there are no foreign objects stuck in them.

If you suspect something's stuck inside the splines, try using a vacuum to suck it out.

3. Inspect the bearings

Continuously variable transmission gearbox repair closeup.

Check the bearing housing and the bearings themselves. If the bearings are loose or rusty, they can make a squeaky noise. If the bearings appear to be worn out, you're better off replacing the blower motor. 

4. Check the blower motor's fuse

A fuse is a device that controls the flow of electricity. It’s found in every electrical appliance, including computers and TVs. When something causes too much current to flow through it, the fuse shuts off the flow of electricity. 

A fuse will blow if it has been exposed to an overcurrent. Overcurrent means that the current is above a certain threshold and the current is not interrupted by a break in the circuit, causing overload.

Another cause of overcurrent is a short circuit in the electrical system. A short circuit is when an electric current flows through a path that's too short to allow the flow of the electric current to be controlled.

A short circuit occurs when there is no resistance or impedance in a circuit. 

How to test a fuse 

The most common method is to use a multimeter (also known as a volt-ohm meter). You can test a fuse by connecting a small probe to the terminals at either end of the fuse.

By checking its physical condition, you will also know if the fuse is blown. If you see a broken wire in the fuse, then it's a blown fuse.

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5. Check the blower motor's resistors

Resistor motor blower

The blower motor has a resistor assigned for each fan speed. Resistors are used to control current flow through circuits. The resistance of a resistor is the amount of electric potential (voltage) required to pass a certain amount of current.

In other words, a high fan speed setting will require a resistor that has more voltage to power it up than the resistor for a low fan speed setting.

If the blower motor only works at a high fan speed setting, then there's possibly something wrong with the resistor for the low fan speed.

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How to test a resistor

A resistor can be tested using a multimeter. To check the value of a resistor, just connect the two ends of the resistor in series with the multimeter.

Then connect one lead to the positive terminal and the other lead to the negative terminal of the multimeter.

If you see a voltage drop, then your resistor is good. If you don't, it might be damaged or a faulty resistor. You're better off replacing the entire blower motor assembly if you've diagnosed at least one faulty resistor.

6. Check the connectors of the resistors and the blower motor

A connector is a fitting component that connects two electrical cables, wires, or other electronic and mechanical components.

Connectors are made of plastic or synthetic rubber and may be designed to allow for a quick connection and disconnection between the cable and the device.

They are usually molded to have strain relief and often have a threaded or bayonet style fastener to ensure a secure connection. 

How to check the connectors

The physical condition of the connectors should give you an idea of whether they are good or not. If the connectors have any cracks or signs of corrosion, it is a good indication that they are old and need replacement.

Check for bent or damaged pins. The wires should also be inspected for any signs of wear, damage, or deterioration.

Connectors are also checked by using a multimeter to check the continuity. Take out the connector from the blower motor and the resistors and measure continuity across the terminals.

If the continuity is open, replace the blower motor with a new one. If continuity is found, you can use it for further testing

7. Check the cabin air filter

Replacing the dirty cabin pollen air filter for a car

A cabin air filter is a part of the ventilation system of an automobile that cleans and freshens the air inside the vehicle.

A cabin air filter is used to trap dust particles, pollen, and other impurities that enter the vehicle's interior through the ventilation system. The cabin air filter should be changed somewhere between every 15,000 and 30,000 miles.

The first sign that your cabin air filter needs replacing is when the air feels "dirty". If you feel a musty smell or smell of mildew, this is a good indication that your filter is clogged.

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In addition, delaying the replacement of your cabin air filter may cause the accumulation of dust in the filter, which can increase the resistance of the filter and decrease its efficiency.

You also run the risk of tearing the filter apart, so don't be surprised if there are small particles and debris getting through the filter to the blower motor.

Watch the video below for a simplified explanation:

How Much Does It Cost To Fix Or Replace A Car's Blower Motor?

You can get an estimate of how much it will cost to repair or replace a car's blower motor by contacting a reputable auto repair shop. Most of these shops will give you a free estimate when you bring your vehicle in for service.

Some of the costs associated with repairing a car's blower motor include labor, parts, and repairs. A blower motor may need to be repaired if it does not function properly or if it is damaged. 

The cost of repairing a car's blower motor will depend on the type of blower motor and the severity of the issue. In some cases, it may cost more to repair than it does to replace a motor.

If a repair won't fix the problem with your blower motor, then a replacement is required. If you are looking to replace the blower motor of your car, you can expect to pay around $130 to $200.

Can You Drive Without A Blower Motor?

Technician in the service center install and maintenance blower air of car and use screwdriver remove a bolt in process,service concept

Driving a car without a blower motor is possible but it might not be a good idea. Without a blower motor, the engine will not be able to expel enough hot air. This will cause the engine to overheat and eventually quit.

In Closing

A rattling noise in a car is a common occurrence. A good way to determine whether the rattling noise is coming from the air vent is to listen to the noise for a while and see if you can pinpoint its source.

Rattling noises coming from the air vent can be caused by debris in the blower motor or a damaged blower motor. The blower motor may need to be repaired or replaced if it isn't functioning properly. 

You might also be interested in these articles:

How To Pull A Vacuum On A Car Air Conditioner?

Why Does My Car Air Conditioner Smell Like Rotten Eggs?

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