Engine pulley stopping and starting while idling

2014 SUBARU CROSSTREK
34,000 MILES • 2.0L • 4 CYL • 4WD • AUTOMATIC
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DEREKREID1980
  • MEMBER
  • 2 POSTS
There is one pulley on the belt drive that starts and stops sporadically. at times it goes backward and makes a clunking noise when it starts or stops. is this normal?
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Feb 10, 2019 at 9:57 PM
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MPNANTO
  • ✓ASE Certified Mechanic
  • 17 POSTS
  • ASE Certified Mechanic
Hi Derek,

Thanks for visiting 2CarPros.

What you are looking at is your A/C clutch, it is normal for it to start and stop. The backwards rotation is also normal. The clutch engages to allow the compressor to spin this is what moves the refrigerant through your A/C system. When the A/C is not on the clutch disengages allowing the pulley to spin without moving the refrigerant through the system.

The backwards turn is the high and low sides equalizing. Once the clutch disengages the valve closes and the compressor vanes are pulled.
Feb 10, 2019 at 10:29 PM
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DEREKREID1980
  • MEMBER
  • 2 POSTS
Thank you very much. I just bought it today and was worried it was something serious.
Feb 10, 2019 at 10:36 PM
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MPNANTO
  • ✓ASE Certified Mechanic
  • 17 POSTS
  • ASE Certified Mechanic
You are welcome!

Thanks for letting us help.
Feb 10, 2019 at 10:38 PM
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