Thump noise when turning on A/C

[tmhamm09]

When turning on A/C recently heard and felt a thump or knocking noise in passenger side.

 

If I leave A/C on and turn there car off, I hear the thump when I start the vehicle. Today, A/C decided not to cool for 5-10 min then thumped on. 14 FTC titanium with 59k, a bit early for A/C compressor to die?!? Will test pressure and leak check, any other ideas would be helpful, the compressor is not cheap?!?

[Juliecat44]

The dealership has had my 2016 for 8 business days for no AC.  Mine “thumped” just like yours.  Leak tests and AC system pressure test were negative.  A corporate tech informed me the front and/or rear evaporators are a known problem, more commonly the front.  The dealership is now tearing apart the interior of the rear of my vehicle to get at the rear evaporator.  My dealership STILL doesn’t have a diagnosis, but I subverted them, reaching out to Corporate to get some insight.  Hope this helps!

[808tc]

I have a 2019 that has about 500 mi that started making a thumping noise intermittently.  It can slightly vary in pitch and volume but seems to be coming from the rear evaporator unit (under the drivers seat) and possibly under the dash (front evaporator unit).  The noise seems to be caused when the rear a/c in turned on and off using either the rear knob or front button.  It will also make the noise intermittently when the rear a/c is  on cycling by itself.  I also tested with the engine off and it  will also do it if the rear a/c is turned on  and off.  The a/c operations doesn't seem to be affected, just a thumping noise.  Has anyone been successful in diagnosing the noise?