Diagnosis
The timer programming is misunderstood or was incorrectly set. The timer button on this model is a cycle, not a simple on/off.
How to Fix It
To set a shut-off timer: With the fan ON, press the Timer button repeatedly. The display will cycle through 0.5, 1, 2, 4, 8 hours. The number shown is how long the fan will run before automatically turning off. Stop pressing when your desired time is displayed. The timer icon will light up.
If That Didn't Work
Performing a soft reset (unplug for 60 seconds) can clear any glitch in the timer circuit. After resetting, reprogram the timer.
Heads Up
The timer is only for automatic shut-off. There is no 'delay start' function. Also, if you turn the fan off manually before the timer ends, the timer setting is cleared.