C-F3 Moderate Easy DIY

Samsung Microwave C-F3 — Voltage / Frequency Out of Range

Samsung Microwave · Error code C-F3

What C-F3 Means

The control detected line voltage or frequency outside the acceptable window (typically below ~90 VAC or above ~135 VAC, or wrong Hz).

Symptoms

  • C-F3 on power up
  • Microwave will not start
  • Lights may dim in the house when other appliances run

Common Causes

1
Low or unstable wall voltage

Brownout, overloaded circuit, or shared circuit dropping below spec when the magnetron pulls current.

2
Extension cord or undersized circuit

Microwave should be on a dedicated 20 A branch — extension cords drop voltage badly.

3
Wrong-voltage installation

120 V unit plugged into a non-US supply, or vice versa.

4
Failed main control voltage sensor

PCB misreads incoming AC.

How to Fix It

  1. Unplug the microwave and remove any extension cord or power strip.
  2. Plug directly into a known-good 120 V outlet on a dedicated circuit.
  3. Measure outlet voltage with a multimeter under load (target 114–126 VAC).
  4. If voltage is in range and error persists, replace the main control board.
  5. If voltage is low, call an electrician to address the branch circuit.

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.

Common replacement Plug-in outlet voltage monitor View on Amazon→ Common replacement Samsung microwave main control board View on Amazon→

More Samsung Microwave Codes

-dr- -dr- — Door Open (Demo / Reminder) 5E 5E / SE — Touchpad Shorted (Older Spelling) C-21 C-21 — Cavity Over-Temperature C-22 C-22 — Cavity Thermistor Open C-A0 C-A0 — Communication Error Between Boards C-A1 C-A1 — Humidity Sensor Open Circuit

All Samsung codes → All microwave codes →

Verified against manufacturer documentation: samsung.com

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician.