Microwave displays H99 and stops heating; may occur intermittently during longer cook cycles.

Safety: Disconnect power before inspection. High-voltage components should only be serviced by trained personnel.

• Check airflow: Verify that the microwave's intake and exhaust vents are not blocked by cabinets, wall coverings, or items on top of the unit.
• Clean filters: For over-the-range Monogram microwaves, remove and clean the grease filters and check any charcoal filters for blockage.
• Listen for cooling fan: During operation, you should hear the internal cooling fan. If it is not running, the cooling fan motor may be defective.
• Technician service: If H99 persists, a technician should inspect the inverter board, magnetron, and cooling fan for overheating and replace any failed components.