F3H Moderate Moderate DIY
Whirlpool Microwave F3H — Humidity Sensor Out of Range
Whirlpool Microwave · Error code F3H
What F3H Means
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.
Symptoms
- 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
Common Causes
1
Failed humidity sensor
The most common cause — sensors degrade from steam and grease.
2
Grease film on the sensor face
A coated sensor reads incorrectly even when electrically fine.
3
Loose wiring or connector at the sensor or control
Vibration over the range can back a small connector out.
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).
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.
More Whirlpool Microwave Codes
Verified against manufacturer documentation: applianceaid.com
Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician.