What F3H Means
JennAir's F3H page names the humidity thermistor or the associated wiring. It is the sensor that lets the microwave judge when food is done by the steam coming off it, which is why sensor-cook programs are the first thing to misbehave when it fails.
Common Causes of F3H
- A humidity thermistor that has failed
- Grease film over the sensor vent dulling its response
- Damaged wiring between the sensor and the control
🔧 One Safe Check You Can Try
Reset at the breaker for a minute, then use a manual time-and-power setting rather than the sensor programs - manual cooking normally still works while this code is active.
⚠ Why You Shouldn't Go Further Than That
- The sensor sits in the vent path where cooking grease collects, so what looks like a failed part is sometimes a cleaning job that still needs the unit opened to reach.
- A sensor refitted a little out of its original position keeps misreading even when the part itself is brand new.
- Reaching the vent path means taking the microwave down and separating it from the house duct, and a poorly rejoined duct sends steam into the cabinetry.
Opening a panel to inspect or repair something yourself doesn't automatically cancel your manufacturer's warranty — but it can risk accidental damage, and some manufacturers do have specific service conditions. Check your product's warranty terms, or ask us, before deciding.
Technical Reference
- Code
- F3H
- Appliance
- JennAir microwave
- Maker documentation
- JennAir owner manuals and use & care guides
- Checked
- September 2026
Code meanings can change between control generations. Before acting on a code, match the full model number on your appliance's rating label against the manual for that model. We are an independent repair service, not affiliated with Whirlpool Corporation.