Car Heater Making Whining Noise [Explained]

Car Heater Making Whining Noise! Like you, we also experienced this issue and heard the whistling noise only when the HVAC system is on. First, we thought it was the transmission that makes this annoying noise. But soon noticed, that the rattling noise goes in vain when we shut the heater off. 

After going through this problem, we figure out the reason that causes the car heater to make a rattling noise. And today, we will introduce you to all the possible culprits responsible for this issue. So, keep reading. 

Car Heater Making Whining Noise [Explained]

Your car heater is making a whining or whistling noise for different reasons. Debris in the blower, loose alternator belt, and worn-out bearing of the fan motor are some of the culprits that cause your car to whine when the heater is on. 

Therefore, a faulty actuator, loose duct valve seals, improper gap between the squirrel cage & fan housing, and a faulty blower motor are also to blame if the car heater produces high-pitched noise. 

This chapter will explain each of the issues that cause the whistling noise when the heater is on. Also, we will provide solutions to stop the whining noise. 

Note: You can also read how to fix replaced blend door Actuator still not work problem.

1. A Piece Of Debris In The Blower

A leaf or pine needles and other foreign objects may become stuck in the blower and it’s common. This object that gets stuck in the blower will make annoying noise by spinning around the system when you turn on the fan. 

Solution:

Removing the foreign objects from the blower will eliminate the rustling sound coming from the heater. Just remove the blower motor and use an air nozzle to blow away the leaves. You can find the blower motor under or behind the dash passenger side. It’s usually right behind the glove box. 

Alternatively, you can use a shop-vac with a narrower nozzle to remove the leaves if you don’t feel comfortable taking apart the blower motor. 

We suggest you replace the cabin air filter to avoid future debris or leaves getting stuck in the blower motor. 

2. Alternator Belt Comes Loose

Car belt squealing when the heater is on! If this is the issue you encounter, check the alternator belt first. When you turn on your heater fan, it’s drawing a few amps and causing the alternator to work harder. Consequently, belt slippage will occur and create a squeaking noise. 

Solution:

Tightening up the alternator belt will fix the rattling sound in most cases. In this case, tighten up the belt. On the other hand, if the alternator belt gets completely worn out, you need to replace it. Fortunately, it doesn’t cost you a fortune to change the alternator belt. In this case, the following video will come in handy: 

3. A Bad Or Worn Bearing

You will experience the high-pitched whining noise from the heater if the bearing in the fan motor gets worn out. If the bearing gets worn out, the motor will struggle to spin freely. Consequently, it will make a rattling noise. 

Solution:

Generally, worn-out bearings in the fan motor require you to replace the complete fan assembly. However, you can wait until it gets completely faulty. Just lubricate the bearings by adding oil to them. 

To do this, you need to remove the fan assembly. You can easily get access to the fan assembly by making a way under the dashboard on the passenger side. Then, remove the bolts that hold the fan in place and pull out the fan assembly. We highly recommend you replace the fan assembly to solve the squeaking noise. 

4. Defective Vent Blend Door Or Actuator

The actuator controls the vent blend door for a specific function. It moves the vent blend door for temperature changes, defrost mode, recirculation, fresh air, and so on.

If the vent blend door or actuator is at fault, it will make a slapping noise when you turn the heater fan on. 

Solution:

Remove the dashboard to gain access to the vent blend door or actuator. Check the cable or actuator that controls the vent blend door.

Ensure the cable doesn’t get damaged and the actuator is working properly. Otherwise, you need to replace the actuator. And the following video will help you to change the blend door actuator: 

5. Loose Duct Valve Seals

Loose duct valve seals cause the hot air to escape from the heater and produce a rattling noise.

These seals may come loose if the screws that hold them in place are wobbling. In the worst case, the duct valve seals get worn out completely. 

Solution:

First off, check the screws that keep the duct valve seals in place. Fasten them if needed. On the other hand, you need to replace the duct valve seals if they get damaged. 

6. Blower Motor Squirrel Cage Touches the Fan Housing

The squirrel cage is basically a metal cylinder that has fins on it. These fins spin inside the blower motor. When the fins touch the fan housing, they make a squeaking sound and prevent the fan from working properly. 

Solution:

Ensure the squirrel cage doesn’t get bent. Then, adjust the gap between the squirrel cage and the fan housing. If needed, you should replace the blower motor squirrel cage. 

7. Defective Blower Motor

A failed blower motor is another suspect that causes whistling noise. The noise will increase with the increase of the fan speed.

In this case, there is no option except to change the blower motor with a new one. 

Solution:

It’s easy to replace the blower motor. First off, pull out the glove box underneath the dashboard. Then, detach the electrical connector (blower motor wiring).

Finally, remove the blower motor and install a new one. We recommend you take a look at the following video that will help you replace the blower motor: 

Conclusion

Debris in the blower was the culprit that made our car produce the whining noise. But there are other culprits that cause this issue. A loose alternator belt, worn-out bearing in the fan motor, and defective blower motor are some of them. 

Fortunately, we broke down everything that causes your car heater to make the whistling noise. So, follow the troubleshooting steps we mentioned to stop the annoying noise.