--- title: "Microwave runs but does not heat" description: "Whirlpool microwave not heating — whirlpool microwave runs but does not heat: a microwave that lights, turns and counts down while heating nothing has a hi" url: "https://whirlpoolmiami.support/symptoms/microwave-not-heating/" date_modified: "2026-09-06" Appliance type: "Microwaves" --- # Whirlpool microwave runs but does not heat ### One safe test, and one thing not to do Put a cup of cold water in the microwave and run it on full power for one minute, then feel the water. Warm means the magnetron is producing something and the problem is more subtle than it looks. Stone cold means it is producing nothing. That is the whole of what can be tested safely from outside the case. Do not open the cabinet. The capacitor inside a microwave stores enough energy to injure or kill someone long after it has been unplugged, and there is nothing in there that a homeowner should be reaching for. ### What it usually means, by the kind of machine Whirlpool sells one appliance in several forms — a top-loader with an agitator and one without, a front-loader, a stacked pair, a laundry tower and an all-in-one; a vented dryer, a ventless one and a heat pump — and the same behavior points at different things on each of them. A top-load washer has no drain pump filter to open and a front-loader does, which is the whole first hour of the same complaint on two machines. - **Over-the-range** — Doubles as the hood over the range, so a microwave that will not heat may still be needed for ventilation. Say if the fan and light still work. - **Built-in** — Set into a cabinet or stacked with a wall oven. Whirlpool publishes a separate no-power page for these, and access is the difference on the visit rather than the diagnosis. - **Countertop** — The one case where the value of the repair has to be weighed honestly against the price of the appliance, and we will say so rather than quote around it. ### Why this page is shorter on advice than the others Every other symptom on this site has something an owner can usefully check. This one really does not, beyond the water test, and we would rather say that than pad the page out. The high-voltage section of a microwave is genuinely dangerous to anyone without the equipment to discharge it, and the internet is full of advice that skips over that. Whirlpool’s own pages for these codes stop at a power reset and then send you to a technician, which is the same conclusion for the same reason. ### What the visit settles We measure the high-voltage circuit properly, read whatever the control has stored and check the door interlocks, and then tell you plainly whether the repair is worth doing. On a built-in or an over-the-range unit that matches the rest of the kitchen, it usually is. On a countertop machine it often is not, and you will get that answer from us rather than a quote that quietly assumes otherwise. The magnetron The part that makes the microwave energy. When it fails, everything else keeps working perfectly and nothing gets hot. The high-voltage diode or capacitor Common failures and often accompanied by a buzz or a smell. Only ever handled with the charge safely bled off. A door interlock switch The microwave will not produce energy unless it is certain the door is closed. A worn latch can leave a machine that runs and does not cook. A temperature sensor circuit Whirlpool codes E21 as the thermal sensor circuit reported open to the control board, and F4 E1 as the cavity temperature thermistor. The control board F6 E0 and F9 are both Whirlpool's report that the oven could not execute the function, pointing at the appliance control board or its wiring. Run the cup-of-water test One minute, full power, then feel it. It is objective, it is safe, and it tells us more than a description of the food. Listen for a change in the hum A microwave with a failed high-voltage part often sounds different — louder, or with a buzz that pulses. Say so if you hear it. Note any code exactly E21, F4 E1, F6 E0 and F9 are all real entries in Whirlpool's own table and each points somewhere different. Check whether the fan and light still work On an over-the-range unit that decides whether you still have ventilation while you wait for the repair. The plate turns, the light is on, the food is cold What it usually means A microwave holds a lethal charge in its capacitor after it is unplugged — this one is not a home repair E21 is Whirlpool's thermal sensor circuit reported open; F4 E1 is the cavity temperature sensor The one safe test is a cup of water and a clock One safe test, and one thing not to do Put a cup of cold water in the microwave and run it on full power for one minute, then feel the water. Warm means the magnetron is producing something and the problem is more subtle than it looks. Stone cold means it is producing nothing. That is the whole of what can be tested safely from outside the case. Do not open the cabinet. The capacitor inside a microwave stores enough energy to injure or kill someone long after it has been unplugged, and there is nothing in there that a homeowner should be reaching for. What it usually means, by the kind of machine Whirlpool sells one appliance in several forms — a top-loader with an agitator and one without, a front-loader, a stacked pair, a laundry tower and an all-in-one; a vented dryer, a ventless one and a heat pump — and the same behavior points at different things on each of them. A top-load washer has no drain pump filter to open and a front-loader does, which is the whole first hour of the same complaint on two machines. Over-the-range — Doubles as the hood over the range, so a microwave that will not heat may still be needed for ventilation. Say if the fan and light still work. Built-in — Set into a cabinet or stacked with a wall oven. Whirlpool publishes a separate no-power page for these, and access is the difference on the visit rather than the diagnosis. Countertop — The one case where the value of the repair has to be weighed honestly against the price of the appliance, and we will say so rather than quote around it. Why this page is shorter on advice than the others Every other symptom on this site has something an owner can usefully check. This one really does not, beyond the water test, and we would rather say that than pad the page out. The high-voltage section of a microwave is genuinely dangerous to anyone without the equipment to discharge it, and the internet is full of advice that skips over that. Whirlpool’s own pages for these codes stop at a power reset and then send you to a technician, which is the same conclusion for the same reason. What the visit settles We measure the high-voltage circuit properly, read whatever the control has stored and check the door interlocks, and then tell you plainly whether the repair is worth doing. On a built-in or an over-the-range unit that matches the rest of the kitchen, it usually is. On a countertop machine it often is not, and you will get that answer from us rather than a quote that quietly assumes otherwise. ### Is it safe to keep using it in the meantime? If it heats nothing, there is little point, and if there is any smell of burning or any arcing inside the cavity, stop using it now and unplug it. A microwave that sparks is not something to finish the week with. ### It heats sometimes and not others. Intermittent heating usually points at the high-voltage components starting to fail rather than at anything to do with the food or the settings, and it generally becomes permanent quickly. Worth booking while you can still choose the day. --- **[Read full article: Microwave runs but does not heat](https://whirlpoolmiami.support/symptoms/microwave-not-heating/)**