Whirlpool · Microwave Moderate
F3H — Humidity Sensor Out of Range
The humidity (steam) sensor used for Sensor Cook and Sensor Reheat is returning a value outside the valid range. Sensor cooking won't work; manual cook usually still does.
- Keep using it?
- Yes, with caution
- DIY difficulty
- Moderate
- Verified against
- applianceaid.com ↗
How to fix it
- Power down at the breaker for 1 minute and retest with a manual cook cycle.
- Locate the humidity sensor (usually in the exhaust path on top of the cavity) per the model's tech sheet and clean its face with a dry brush. No water inside the cavity opening.
- Reseat the sensor's connector at the control board.
- If F3H returns on a sensor-cook cycle, replace the humidity sensor.
- If a new sensor doesn't fix it, replace the main control board (it provides the sensor's reference voltage).
Why it happens
Typical signs: F3H or F3-H on the display · Sensor Cook / Sensor Reheat / Popcorn fails immediately · Manual time cooking still works · F3H appears partway through a sensor-cook cycle
- Failed humidity sensor The most common cause — sensors degrade from steam and grease.
- Grease film on the sensor face A coated sensor reads incorrectly even when electrically fine.
- Loose wiring or connector at the sensor or control Vibration over the range can back a small connector out.
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 sensor 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: applianceaid.com.