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
- 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).
- Reseat or repair the harness; an out-of-spec thermistor gets replaced.
- 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 replacementAmazon →
More Whirlpool 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: producthelp.whirlpool.com.