Frigidaire · Microwave Serious
F1 — Control board / thermistor open
F1 indicates the main control board has detected a fault, commonly an open thermistor circuit or a self-diagnostic failure on the control. The unit usually will not run until cleared.
- Keep using it?
- Limited use only
- DIY difficulty
- Moderate
- Verified against
- frigidaire.com ↗
How to fix it
- Unplug for 5 minutes to attempt a soft reset.
- If F1 returns immediately, open the control compartment and reseat all connectors on the main board.
- Locate the cavity thermistor in the tech sheet — measure resistance at room temp (typically 50–100 kΩ depending on model).
- Replace the thermistor if resistance is open or wildly out of spec.
- If thermistor is good and connectors are tight, replace the electronic control board.
Why it happens
Typical signs: F1 displayed · Microwave will not start · Display dim or stuck · Continuous beep on power-up
- Failed control board (ERC) Most common — internal logic fault triggers a hard F1.
- Open or shorted oven cavity thermistor Some models alias thermistor faults to F1; check resistance per tech sheet.
- Loose harness connector to control Vibration or service work left a connector partially seated.
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.
More Frigidaire 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.