When newly acquired, the long gone school bus yellow (brown interior) 1978 245 had enough leaves in the gutter and frame to fill a garbage can. The fix after cleaning was shoving an open weave kitchen scrubber partially into the two drains. It was too big to shove all the way into the drain. Note that '78 probably had 3/4 inch openings between the grills.

The 1992 244 has much smaller gaps but needed a modification to do as good a job as the 940s with the screen under the grill.

My intention was to get a screen fastened to the underside of the grill. The stiffer dog screen was still too flimsy and I am still looking for a house gutter guard type screen, a little stiffer but fold-able.

The photo shows a dog proof screen installed on the top. It is glued in place with a sticky 3M non-hardening rope type sealant. No noticeable affect to fresh air volume even with the fan off.

If I think of it I will try a gutter screen from a junked 940.

Tom