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

How to fix it

  1. Power down at the breaker for 1 minute and retest with a manual cook cycle.
  2. 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.
  3. Reseat the sensor's connector at the control board.
  4. If F3H returns on a sensor-cook cycle, replace the humidity sensor.
  5. 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 replacement
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Frequently asked questions

What does the F3H code mean on a Whirlpool microwave?

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.

What causes the F3H code on a Whirlpool microwave?

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.

Is it safe to keep using a Whirlpool microwave with a F3H error?

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

How do I fix F3H on a Whirlpool microwave?

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.

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