Loud thump from under dash when starting AC

[Tango Yankee]

When I start the AC there is a loud thump from under the dash, like a vent damper closing. It is 100% not the magnetic compressor pulley kicking in. The thump is definitly too loud and will need fixed.

 

2013 GMC Sierra 1500 SLE

 

Thanks.

[GMCustomerService]

1 hour ago, Tango Yankee said:

When I start the AC there is a loud thump from under the dash, like a vent damper closing. It is 100% not the magnetic compressor pulley kicking in. The thump is definitly too loud and will need fixed.

 

2013 GMC Sierra 1500 SLE

 

Thanks.

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[KARNUT]

My 02 avalanche does that sometimes. I can feel it as well sometimes. I remember my 01 and 04 did that too even when new. I figured it was the compressor or even the AC line. 

[KARNUT]

4 minutes ago, KARNUT said:

My 02 avalanche does that sometimes. I can feel it as well sometimes. I remember my 01 and 04 did that too even when new. I figured it was the compressor or even the AC line. 

I just realized that since I had my AC serviced two weeks ago it is less intense. 

[richard wysong]

Maybe the recirculate door closing?