Whirlpool · Microwave Moderate

F4E4 — Humidity Thermistor Fault

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.

Keep using it?
Yes, with caution
DIY difficulty
Moderate
Verified against
producthelp.whirlpool.com ↗

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.

Why it happens

Typical signs: F4E4 on the display · Sensor Cook / Steam / Reheat fails immediately · Code returns even after a full power cycle

  • Failed humidity thermistor Resistance drifts open or shorts — most common cause.
  • Damaged thermistor wiring Wires routed through hinge or vent area can chafe.
  • Loose connector at the control board Check both ends of the harness.

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.

  • Whirlpool microwave humidity thermistor Common replacement
    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 Manager or Power Relay Fault F1E5 F1E5 — Inverter Internal Fault F2 F2 — Keypad / Control Fault

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Frequently asked questions

What does the F4E4 code mean on a Whirlpool microwave?

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.

What causes the F4E4 code on a Whirlpool microwave?

Failed humidity thermistor: Resistance drifts open or shorts — most common cause. Damaged thermistor wiring: Wires routed through hinge or vent area can chafe. Loose connector at the control board: Check both ends of the harness.

Is it safe to keep using a Whirlpool microwave with a F4E4 error?

Yes, with caution. This is rated a moderate-severity fault.

How do I fix F4E4 on a Whirlpool microwave?

Power down at the breaker for 1 minute and retest. Unplug or kill the breaker, then access the top of the cavity per the install / tech sheet. Disconnect the humidity thermistor and check resistance against the spec on the model's tech sheet (typically around 10K ohms at room temp).

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: producthelp.whirlpool.com.