AC Makes a Hissing Noise? Car Heater Rattling? How to Fix

If your car’s AC makes a hissing noise when it’s turned on, or if you hear a rattling sound when your heater is turned on, there might be a simple, easy and quick fix. Find out how to fix a car AC that makes a loud sound like hissing, rattling, or humming by inspecting the blower motor with the tips in this article and video.

How to Fix a Car AC Hissing or Heater Rattling Noise

1A Auto mechanic reviewing how to diagnose an AC that makes a hissing noise or heater making a rattling sound

If you’ve turned on the air conditioning (AC) or the heater in your car and you hear a rattling, hissing, humming, or similar loud noise from under the dash, follow these steps to diagnose it.

How to Fix Car AC Hissing Sound or Heater Rattling Noise

  1. Remove the Blower Motor

    Most cars have a blower motor located underneath the dash on the passenger side. You might have to remove the glove compartment or a lower trim panel to access it. Blower motors are usually easy to remove and require removing a few screws and disconnecting an electrical connector to remove it.

    Find a video specific to your year, make, and model in our how-to video library

  2. Inspect the Blower Motor for Debris

    Check the blower motor for any debris that may be caught inside, like trash, pine needles, acorns, and more. Sometimes debris can get caught inside and cause a humming noise from the blower motor when the fan settings are turned up.

    If you find debris, remove it from the blower motor.

  3. Reinstall and Test the Blower Motor

    After removing debris, install the blower motor by tightening the screws and reconnecting the electrical connector. Turn the fan up to its highest settings and see if the loud humming, rattling, or hissing sound returns.

  4. Consider Replacing the Blower Motor

    If cleaning the blower motor of debris and reinstalling it didn’t fix this problem, you probably need to install a new blower motor.

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AC Makes Hissing Noise? Car Heater Makes a Rattling Sound? - 1A Auto
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AC Makes Hissing Noise? Car Heater Makes a Rattling Sound? - 1A Auto
If you have a car with an AC that makes a hissing noise or a heater that makes a rattling noise, find out how to fix it quickly and easily with these tips from professional mechanics
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1A Auto
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