So, I get a significant thump noise (and slight car shake) about every 30 seconds when my HVAC is on. The HVAC works fine. It might be happening when the car is moving but it's not noticeable then. HVAC set to 21C so warmer than outside, but not significantly so. When I first noticed it (when sitting at a red light) I assumed I must have not been pressing the brake hard enough and hence the creep mode was somehow pulling a bit, but after doing some experiments it definitely seems to just be HVAC related. I can sit in the car, with "car off" on the dash, and every 33 seconds I hear/feel the thump. Turn off the HVAC and no thump. Pretty sure it's only been happening for the last month or so. Anyone else have this?