Whirlpool [F4E4] fault codewhat it means and how to fix it

Both of Whirlpool’s sources agree on this one: a humidity sensor error on the tech sheet, a microwave humidity sensor on the public page. What is odd is that Whirlpool publish the identical component description under a second, differently formatted code as well — F3H, which their public page also gives as microwave humidity sensor. Two codes, one part, no published explanation of the difference. It is worth knowing because it means a search for either string is a search for this fault, and because it is a small example of what the whole Whirlpool code space is like.

The sensor itself is what makes automatic cooking possible. A sensor-cook or auto-reheat programme does not know what you have put in, so it runs at power until it detects the steam coming off the food, uses that moment to estimate how much there is, and then sets the remaining time from it. The sensor is in the exhaust path, because that is where the steam goes. That placement is why this code is more often about the path than the part. A sensor coated in cooking residue reads late or not at all; an exhaust filter or vent choked with grease keeps the steam from reaching it; and covering the food tightly, which people do to stop splatter, has the same effect for the same reason.

So the failure Whirlpool report as a sensor error frequently starts as an appliance nobody has cleaned. The consequence is limited and that is why this page is rated as information rather than a fault to stop for. Every manual function still works. What stops working is the automatic programmes, and the sensible interim is to cook by time and power level, which is what everybody did before sensors existed.

1. 1

   Switch to a manual time-and-power programme. If everything works that way and only sensor or automatic programmes fail, this code is behaving exactly as described.

2. 2

   Clean the vents and the grease filter if there is one. On over-the-range and built-in models this is routine maintenance that is skipped for years at a time.

3. 3

   Wipe the cavity and the area around the exhaust opening, and leave the door open for a while to let any residual moisture clear.

   Clean the visible openings only. The sensor is inside the appliance, and no microwave fault is worth taking a cover off for.
4. 4

   Power cycle it — a minute off, then a minute watching it — and try an automatic programme again with the food loosely covered rather than sealed.

5. 5

   If it persists, decide whether you use the automatic programmes enough to pay for the repair. This is one of the few codes where continuing to use the appliance as it is costs nothing but convenience.