F4E4 Moderate Moderate DIY

Whirlpool Microwave F4E4 — Humidity Thermistor Fault

Whirlpool Microwave · Error code F4E4

What F4E4 Means

The humidity thermistor is reading open or shorted, or its wiring is bad. Sensor-based cook modes will fail; the unit usually still runs manually.

Symptoms

  • F4E4 on the display
  • Sensor Cook / Steam / Reheat fails immediately
  • Code returns even after a full power cycle

Common Causes

1
Failed humidity thermistor

Resistance drifts open or shorts — most common cause.

2
Damaged thermistor wiring

Wires routed through hinge or vent area can chafe.

3
Loose connector at the control board

Check both ends of the harness.

How to Fix It

  1. Power down at the breaker for 1 minute and retest.
  2. Unplug or kill the breaker, then access the top of the cavity per the install / tech sheet.
  3. Disconnect the humidity thermistor and check resistance against the spec on the model's tech sheet (typically around 10K ohms at room temp).
  4. Reseat or repair the harness; an out-of-spec thermistor gets replaced.
  5. If a known-good thermistor still throws F4E4, replace the appliance control board.

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 Whirlpool microwave humidity thermistor View on Amazon→

More Whirlpool Microwave Codes

AccuPop Fail AccuPop Fail — Popcorn Sensor Fault Demo Demo Mode — Not Heating Door Door / Open Door Closed — Safety Reminder F1E4 F1E4 — Appliance Control Board Fault F1E5 F1E5 — Inverter Internal Fault F2 F2 — Keypad / Control Fault

All Whirlpool codes → All microwave codes →

Verified against manufacturer documentation: producthelp.whirlpool.com

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