Frigidaire · Microwave Serious

F5 — Relay / control output fault

F5 means the control board has detected an internal relay feedback mismatch — a relay (often magnetron, fan, or turntable) did not switch as commanded. Usually a control-board failure.

Keep using it?
Limited use only
DIY difficulty
Moderate
Verified against
frigidaire.com ↗

How to fix it

  1. WARNING: Microwave HV capacitors can store a lethal charge — discharge before probing HV components.
  2. Unplug and wait 5 minutes; retry once.
  3. If F5 persists, inspect harness from control board to fan, turntable, and HV transformer for breaks.
  4. Verify magnetron and HV diode are not shorted (ohms test, capacitor discharged).
  5. If HV side checks good, replace the electronic control board.

Why it happens

Typical signs: F5 on display · Microwave may run but not heat, or fan runs constantly · Fault appears shortly after start

  • Failed relay on control board Stuck or burnt relay contacts on the ERC.
  • Open magnetron or HV components Loss of expected feedback to the board.
  • Wiring fault to controlled load Broken wire to fan motor or turntable motor.

Parts you may need

If diagnosis points to a failed part, these are the common replacements. As an Amazon Associate we earn from qualifying purchases.

  • Frigidaire microwave control board Common replacement
    Amazon →
  • Microwave HV diode Common replacement
    Amazon →

More Frigidaire microwave codes

Child Lock 'Lock' / 'L' — Child lock engaged Cooling Fan 'Cooling Fan' / Fan-runs-after-cooking — Vent fan stuck on Demo 'Demo' / 'd' — Showroom demo mode on door 'door' message — Door not fully closed F1 F1 — Control board / thermistor open F2 F2 — Keypad / Control Board Input Fault

All Frigidaire codes → All microwave codes →

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician. Verified against manufacturer documentation: frigidaire.com.