What F3 Means
Whirlpool publishes a family of thermistor codes on over-the-range microwaves - F3C, F3H, F3H1, F3T1 through F3T4, F4E1, F4E4 and F4E9 - all with the same description: there may be a problem with the cavity temperature thermistor or the associated wiring. They are grouped here because the owner-facing guidance is identical for every one of them.
Common Causes of F3
- Failed cavity temperature thermistor
- Thermistor wiring or connector fault
- Control board fault
🔧 One Safe Check You Can Try
Unplug the appliance or switch off its breaker for five minutes, then restore power. If any of these codes returns, book a technician and quote the exact characters shown - the service documentation distinguishes them even though the published owner text does not. Do not attempt to reach the thermistor. A microwave capacitor can hold a lethal charge long after the oven is unplugged - this is the one appliance where "unplug it and have a look" is genuinely dangerous advice.
⚠ Why You Shouldn't Go Further Than That
- A microwave capacitor can hold a lethal charge long after the oven is unplugged - this is the one appliance where "unplug it and have a look" is genuinely dangerous advice.
- The thermistor is inside the cabinet beside the magnetron and capacitor.
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.