Why does my thermostat display say FAn in the top corner?
Unexpected status messages like 'FAn' on a thermostat leave people unsure whether the code signals a setting or a routine filter replacement. Without clear instructions, they cannot verify what the alert actually means or figure out how to turn it off once maintenance is done.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1Pulling the thermostat off the wall plate to find the model number and Googling the manual.
- 2Navigating the device's on-screen menu to find the alerts section and read or reset the code.
- 3Assuming it is a routine time-based filter replacement or low battery reminder.
- 4Unpower it by pulling it off the wall and removing batteries for 5 minutes.
- 5Access the configuration menu and change the AC setting to AC1 or AC2.
- 6Search the model number online to find instructions to reprogram it.
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
r/hvacadvice2 people · October 2026
“It says FAn in the top corner. It has never said that before.”source ↗
“Why does my display say FAn at the top corner?”source ↗
extremesauce2468 · r/hvacadvice · 4 upvotes
“That could be it! Just wish I knew for sure, and how to turn it off once I replace the filter”source ↗
StormShockTV · r/hvacadvice · 1 upvotes
Where this came up
People with this problem also raised
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