Microwave Vent Flap Noise . Four bolts were put through the flap towards the bottom to add weight to prevent flap from open so often and reduce the angle of swing and electrical tape was applied where the flap contacts. Leaky house allowing big pressure differences between inside and out? Open Roads Forum Noisy banging range hood exterior vent flap fix?? from www.rv.net Locate the noisy roof vent flapper. Once again, you should set the multimeter to rx1. I resolved the aluminum flap by using teo sided tape to attach steel.