Commercial Chef No Start – Control or Door Interlock Fault

Microwave has power and display, but pressing START does nothing; no relay click, no fan, no light.

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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

Defective START key on membrane keypad, failed door switch not signaling closed, faulty control board relay, child lock still active

How to Fix / Troubleshooting

Safety: Unplug the microwave before internal checks.

User checks:

  • Ensure the door is fully closed and latched; open and close it firmly.
  • Verify that child lock is disabled (see LOC instructions in the manual).
  • Try multiple keys; if only START is unresponsive, the keypad may be failing.

Advanced checks:

  • Remove the control panel and inspect the keypad ribbon cable connection to the control board; reseat if loose.
  • Test door switches for proper operation with a multimeter.
  • If switches and keypad are good, the control board's relay or logic may be defective and require replacement.
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Repair Difficulty

Medium 3/5

Required Part

Membrane Keypad Assembly
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