Skip the auto shop - Our mechanics make house calls

Q: AC knocking when it is turned on

asked by on

I think there is either a problem with the blower or fan belt. When the air conditioner is turned on, it starts making a catching/knocking sound. As soon as it is turned off, it stops.

Hi there. It sounds to me as if your AC’s fan is interfering with something in the track of its spinning. Also your issue can point to your AC compressor clutch not gripping the pulley correctly. I’d suggest having a certified mechanic sent by YourMechanic come to your residence and correctly diagnose the air conditioner’s symptoms that your vehicle is experiencing.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. AC knocking when it is turned on

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Ac water leak by driver side

It is normal for water to leak out of the rubber tube. This tube is called the evaporator drain. It is meant to route the water that comes off of the evaporator core. If the carpet inside the car on...

Q: Wondering condition on a road test.

Hi there. If you are road testing a vehicle to buy, you will want to make sure that the vehicle is safe for road operation. During a road test, if the vehicle is wondering around, there could be multiple things...

Q: Jeep shutting off and then hard to start.

It sounds like there may be a problem with your fuel pump. A lot of times when a fuel pump is starting to go bad it will stop working once it warms up. When it stops the fuel pressure will...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...