I have a 12 year old Whirlpool Microwave + vent hood combo (model GMH5205XVS-1). As far as I know, it should be configured to vent outside (via vent on an exterior wall). If I open the cabinets in the picture, there is a large vent and I can often smell cooking smells outside when the fan is on.

However, the suction above the cooktop is weak, even on the highest fan setting. Yesterday, I noticed there is a big vent at the top of the oven that is also sucking in air. I temporarily blocked it off and noticed it increased suction above the stove.

Is this supposed to be blocked off if the fan is configured to vent to the outside? Or does having suction at the top of the oven provide some other value?

Both the owner's manual and installation manual make no mention of this.

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  • @Traveler I'm not the original owner of the condo, and I don't have any part to seal it. I see a "damper assembly" in the install instructions: whirlpool.com/content/dam/global/documents/201009/… Could that be it?
    – James
    Feb 16 at 21:17
  • Looks like that damper is basically a "check valve" assembly to prevent outside air from flowing in: youtube.com/watch?v=NlP5QUctq9A
    – James
    Feb 16 at 21:23
  • 1
    It is not a damper. Damper usually sits at the end of the exhaust pipe (outside) Its function is to when the exhaust is not running to prevent outside air blowing in when there is wind. It is a small metal flap that is spring loaded (kept closed when the exhaust is not running.
    – Traveler
    Feb 16 at 23:34
  • "Backdraft damper" is the usual term for the device. Just about every exhaust fan has one.
    – kreemoweet
    Feb 17 at 4:52

3 Answers 3


The unit is working as designed: major air movement from below, as is fitting for a "range hood", and minor air flow from the room and around the microwave cabinet to vent moisture/odors. Cabinet-installed microwave ovens require venting of some sort. The horrible open cavities exposed on top of the unit must surely mean there is a missing screen panel of some kind.


There are some instructions in the manual for which way the fan needs to be put in for wall, roof, or in-room venting. Perhaps someone made a mistake in adjusting the fan setup. Taking the hood down and confirming the fan arrangement per the manual may help.

  • 1
    If the fan wasn't rotated for exterior venting air would be coming out of this top opening, not being drawn in.
    – isherwood
    Feb 16 at 21:00
  • I'm 99% sure the fan orientation is correct. Air is sucked in from both the top and bottom of the microwave. I can smell food smells by the exterior vent when cooking
    – James
    Feb 16 at 21:24

Does the vent beneath the microwave hold a tissue up when you have it venting on high? If so, then you’re probably fine, though it would be good to verify the outside ventilation.

I just checked a microwave (different GE model) I installed and verified outside venting. There is some suction from the top vent but not as much as from the range vents.

  • Yeah, mine's the same. These units are for clearing the room, not just the range area.
    – isherwood
    Feb 16 at 21:01
  • Yes, the vent beneath the microwave holds a tissue up with the fan on high.
    – James
    Feb 16 at 21:15

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