Loud bang at engine start


I have, on two separate occasions, had what I would describe as a loud plastic "crack" or "snap" sound come from within the dashboard near the driver's side vent. The sound was produced whether or not the engine was actually cranked: pressing the start button without a foot on the brake also triggered the sound. On each occasion, the GLC would reliably produce this sound on start (if it had been off for more than a few [at least 5] minutes). In both cases, the sound occurred for a couple of days, then vanished. Some googling led me to speculate that it's due to a blend door actuator.





