i have a Chevrolet Spark 2013.I've been hearing a periodic knocking sound like a hammer, whenever i turned on my blow fan.It happens even without changing the thermostat on ac or heat. I figured the sound location from the engine. I saw something like a gear attached on the side of the engine which spins when fan is on, it fully stops, then the knocking sound, then spin again in that sequence, so spin -> stop -> knock -> spin. It does this periodically every 30 seconds.When the fan is off the knocking sound disappears. Is it normal? Should i get to the mechanic asap or leave it for the next scheduled service maintanance? Thanks in advance

  • Welcome to Motor Vehicle Maintenance & Repair! From your descriptions, you've got a problem with your A/C compressor. This is about the only thing up front which makes any noise and is cyclic. When the A/C compressor is turned on by the computer, the fans will also come on. I wouldn't know why it would be making the noise like you describe, but would bet if it's making a noticeable noise, the compressor is going out. Just a guess, though. – Pᴀᴜʟsᴛᴇʀ2 Nov 24 '19 at 19:50
  • please can you record that sound ( video)on your channel in youtube and share the link here as reply, so i can advice you . – Sam Fidal Nov 28 '19 at 14:18
  • @SamFidal youtu.be/yjFxbXSC8vY you can hear the sound at 00.10 second. Thank you – Themis Kontzialis Dec 2 '19 at 20:06

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