The short answer
On Fisher & Paykel a machine that runs without heating is most often a turntable that is not turning. Ranked that way because the door and its interlock stack are the part the owner operates thousands of times, and they wear accordingly.
What you observe
- It hums loudly and still nothing heats — Points at the high-voltage side, which is a technician job.
- The light and the turntable work but nothing gets hot — The classic signature of a lost high-voltage side or an interlock not being pressed.
- NEAR MISS: nothing happens at all when you press start — That is a will-not-start fault rather than a heating one, and it has its own page.
Causes, most likely first on Fisher & Paykel
- The turntable is not turning, so the food is not being moved — First here, where a modulating control hides a developing fault rather than announcing it. A plate off its coupling, or a roller ring jammed by a crumb, leaves the food sitting in one spot. The result is hot edges and a cold centre, which people reasonably report as a machine that does not heat.
- The load is too large, too cold or badly arranged — Second, and the cause this control is least able to tell you about. A microwave heats from the outside in and it heats water best. A dense frozen block, a large dish filling the cavity, or food straight from the freezer will all come out cold in the middle with a machine working perfectly.
- The power level or the programme is not what you think — Third. A machine left on a defrost setting, a low power level or a timed programme without heat will run, turn and light exactly as normal while barely warming anything.
- The magnetron, diode, capacitor or transformer has failed — Last, and it is the reason the order above matters. A cup of water stays cold on full power with the door latching properly.
Check in this order, and why
- Watch whether the plate actually turns during a programme — A stationary plate explains uneven heating with a perfectly healthy magnetron.
- Compare against a cup of water heated on full power — If the water heats and the food does not, the machine is fine and the load is the problem.
- Read the power level and the programme actually selected — It is free, it takes seconds, and it explains a machine with no fault at all.
What an owner can safely check
- Seat the plate correctly on its coupling and clear the roller ring — Wash the ring and the recess it runs in; a crumb is enough to stop it.
Tools: damp clothAbout 10 min
- Heat a cup of water on full power for a short time and feel it — Arrange food in a ring rather than a mound, and stir or turn it part way through.
Tools: a mug of waterAbout 10 min
- Select full power and a short time, and heat a cup of water as a test — Water that is genuinely hot after the test means the machine heats and the setting was the fault.
Tools: a mug of waterAbout 5 min
- STOP HERE if the next step needs a meter on live terminals — That is where an owner check ends and a service call begins.
Before you open anything
Safety
Never open the outer casing of a microwave. The high-voltage capacitor can hold a lethal charge long after the machine is unplugged, and no amount of care changes that. Never tape, pack or bypass a door interlock to make a machine heat, and never run the machine empty to test it: with nothing to absorb the energy it damages itself.
When to call a technician
Call, or replace the machine, when a cup of water stays cold on full power with the door latching properly, because that puts the fault on the high-voltage side. Call as well when the door has to be held, since worn interlocks are a safety part. Stop using it immediately if it hums loudly, smells hot, or arcs inside the cavity.
Nearest pages of this class
What this page does not cover
This page covers the brand and the microwave class, not one family or model line. Where a family-specific or model-specific page exists for your unit, that page is the more specific answer and it takes precedence over this one. Not here: part numbers, wiring colours and component locations, which differ by family.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
