Hi, I’ve been experiencing a knock noise coming from my blower motor or something in contact with that assembly. It is random and fairly infrequent, occurring every minute or two. There is nothing loose in the blower motor and I can’t track this down. The next thing I will try is putting a volt meter on the fan power and see if there is a voltage drop or spike that is causing this. It only happens when on high, can a failing resistor on the motor control do something like this?

Any thoughts?

Thanks

 

I am not sure what is causing your problem, but I am certain that a blower motor resistor would not cause a knocking noise.

Are you 100% sure there is no debris or loose parts near the fan?

Is the cabin air filter installed?