Diagnosis
The control board is receiving the button press but not relaying the command to the fan motor, often due to a software glitch or a failing fan motor control module.
How to Fix It
Reset the unit's control system.
- Unplug the AC from the wall outlet.
- Wait 2 full minutes for all capacitors to discharge.
- Plug it back in. The display will light up. Do not press any buttons for 30 seconds.
- Now try changing the fan speed using the buttons on the unit itself (not the remote).
If That Didn't Work
The fan speed button or its membrane switch on the control panel might be physically stuck or failed. Try pressing it firmly and listening for a distinct click. If there's no tactile feedback, the button mechanism is the problem.
Heads Up
If it works with the unit's buttons but not the remote, the problem is isolated to the remote. Re-pair it (hold the Timer button for 5 seconds while pointing at the unit) or replace the remote batteries with a fresh set from a new pack.