HVACopediaTrane · Furnace troubleshooting
Fit the return air filter
What is going on
The return air filter that comes with the Trane may need trimming, depending on where your return ends up. It is an easy job but do it right: measure first, cut once, and use the score line the maker puts on the filter. A filter that does not fit lets dirty air go around it and into the blower.
Likely causes
- Filter too large for the return opening
- Cut made in the wrong place, damaging the media
- Gaps around the filter after trimming
Check in this order
- Measure the return location to see if the filter needs cutting.
- If cutting is needed, cut the filter on the score line marked CUT HERE at the end of the filter.
- Test-fit the filter and check it sits snug with no gaps.
- Note the filter size on the cabinet or a label so replacements match.
Applies to: Furnace return air filter
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Source: Trane AUH1B080A9421B installer's manual, p. 17. Written in our own words; check the manual for your exact model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.