Microwave displays H0 or HO and will not start; often appears after a power outage.

Note: On some Tristar microwaves, H0/HO is not a fault but an indication that child lock or demo mode is active.

Steps to clear H0/HO:

• 1. Try child lock reset: Press and hold the STOP/CANCEL or 0 key for 3–5 seconds until the display clears or a lock icon disappears. Refer to your Tristar user manual for the exact key combination.
• 2. Check for demo mode: If the microwave runs but does not heat and shows H0/HO, demo mode may be enabled. Press and hold STOP/CANCEL and START together for several seconds (or follow the manual) to toggle demo mode off.
• 3. Power reset: Unplug the microwave for 2–3 minutes, then plug back in and reprogram the clock. Test a heating cycle.
• 4. If H0 persists: If the code will not clear with the above steps, the control PCB may be misreading the lock status and could require replacement.