qiria

Hi all, My octavia 2014 1.2 tsi has been making this strange noise since I got it last year. The dealership have checked the diagnostics and found no faults. It seems to happen randomly, but my suspicions are something to do with the aircon. If i turn the aircon off the noise stops (usually). The aircon seems to work fine. Sometimes the noise happens whilst driving, and sometimes just after the car has been turned off, lasting for about 3-5 seconds. Anyone else have this problem, or know what it is? I'd rather have an idea before giving it to the mechanic to pull things apart trying to find it. Thanks!