Ambient temperature is too high.

Ensure that environmental conditions comply with the operation requirements of the projector. See installation manual of the projector for detailed installation requirements.

Blocked dust filter.

Check the dust filters and clean if needed. See service chapter "Maintenance procedures".

Malfunction fans of the Card Cage. Two bottom fans of the Card Cage are used to cool the SMPS!

Check for error or warnings related to the Card Cage fans and resolve these first.

Malfunction SMPS.

Replace the SMPS. See service procedure "Replacement of the SMPS board".