Microwaves - Vent Getting Louder or Changing Speeds

On over-the-range microwave ovens, you may find the vent fan is changing speeds or getting louder while it is running. This can be normal.

 

Cause:

 

• In both recirculating (with the charcoal filter in place) or in vented applications where the ductwork causes an excessive back pressure on the fan, the fan will automatically kick up to a higher speed when set on high. This is done to compensate for the added back pressure (it will stay on this higher speed at the medium and low settings as well).

 

To Override (places the fan in medium or low speed):

 

• Starting with the vent fan in the off position) press the vent fan pad twice to get to the medium speed, or three times to get to the low speed.

 

If you wish to confirm that the vent is changing speeds:

 

• Push the "VENT FAN" pad followed quickly by the "VENT FAN BOOST" pad. That way the fan shifts from LOW to VERY HIGH as quickly as you can push the pads. You should be able to hear/feel this difference, even with a charcoal filter installed.

 

To view a short video on microwave vent sound level: