I noticed a problem with my furnace filter. In the vertical slot where it gets installed, there is a channel along the bottom but not along the top. As a result, the top corner of the filter furthest away from the opening will bend toward the blower motor and allow air to rush past the filter. How can I fix that without taking apart the whole intake duct?

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Dumb idea #1: Put a series of machine screws along the duct opposite of the filter slot. The filter should push against them when air is flowing and no longer be able to bend. The bad part: Would then be even more of PITA to line up the filter and get it in.

  • 1
    I think Ryobi makes a drill for that.
    – Alaska Man
    Nov 1 '18 at 17:40
  • Call a furnace company and get them to sell you a 1” filter track, you can likely get in installed without taking everything apart. I replaced on in one of my rental houses it was easy, I used a filter itself to level it, and I could reach where I needed to shoot a screw through the blower access panel.
    – Tyson
    Nov 1 '18 at 20:53

Assuming you can find a channel at one of the big box stores you can slide the channel in and maybe screw it in all the way at the end so the screws don't interfere with the filter. In fact it seems like you don't even need a piece of channel. A piece bent like an L should work. When you screw it in offset it so the top of the L is not above the top of the filter. Attached is a drawing. Black is opening, red is L bracket, blue is screw

  • This worked pretty well. At the big orange store I found aluminum angle stock. I took the side off the furnace and was able to get inside the air return and drill+screw the angle stock in place as you suggested. Nov 2 '18 at 17:08

Buy a metal-framed filter that won't bend so easily. These are available from HVAC suppliers and usually include filter media that is washable/replaceable.

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