There are some possible reasons caused, please check below first:

<Airflow>

     Air Flow is important for cooling:

1. Please make sure the intake and exhaust vents are free from obstruction.
2. Make sure the projector is not enclosed or right against a wall - it needs ventilation space.
3. Don’t place the projector on top of other electronic equipment, such as an AV receiver.

<High Altitude>

If the projector is being used in higher altitude you will need to turn on the “High Altitude” mode. The fan will thus operate at a higher speed to intake more air. Please check user guide to enable it.

If above steps don’t help, please contact ViewSonic service center.