VIDEO showing my situation below... I have an electric heater in my garage and the fan motor is vibrating, resulting in a lot of noise. I noticed that if I press my finger against the back of the motor, the sound stops. So, I wedged a piece of wood between the back of the motor and the grate. This stopped the vibration, but I want a more longterm solution. Any ideas on ways I can permanently fix this issue?
It looks like the motor bracket isn't fastened down properly, which allows it to move. Or maybe it's the point where the motor attaches to the bracket. Turn off the fan, take off the grate, and examine it - maybe you just need to tighten some bolts (if you tighten them, and they work loose again, try putting Lock-Tite on the threads.)
If that doesn't fix it, just leave the piece of wood in place. But if you leave it in there long-term, you'll want to fasten it somehow so it doesn't slide down.