H1
Tristar Cavity Overheat / High Temperature Error

Microwave displays H1 or HI and stops heating; fan may continue to run.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Blocked air vents, Failed cavity thermostat, Overuse on high power without rest, Faulty temperature sensor

How to Fix / Troubleshooting

Safety: Unplug the microwave and allow it to cool completely before inspection.

Steps to address H1/HI:

  • 1. Allow cooling: Leave the door open and the unit unplugged for 30–45 minutes. After cooling, plug in and test. If H1 clears temporarily, overheating is confirmed.
  • 2. Check ventilation: Ensure there is adequate clearance around the microwave and that vents are not blocked. Clean dust and grease from vents.
  • 3. Avoid misuse: Do not run the microwave empty or for extended periods on maximum power without food load.
  • 4. Inspect thermostat and sensor: With the cabinet removed, locate the cavity thermostat and thermistor. Test for continuity (thermostat) and proper resistance (thermistor) at room temperature. Replace any component out of specification.
  • 5. If H1 persists: Continued H1 errors after component replacement indicate a possible control board fault or magnetron overheating; contact a technician.
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Repair Difficulty

Hard 4/5

Required Part

Cavity Thermostat
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