The short answer
A Hotpoint microwave that runs but does not heat has usually lost something on the high-voltage side, and that is not owner-serviceable. The first thing to check: magnetron at the end of its life, because the free causes are worth eliminating before a technician is called.
What you observe
- The plate turns, the light is on, the food is cold — The classic loss of the heating side.
- Heating faded over weeks before stopping completely — That history points at the magnetron.
- NEAR MISS — the oven will not start at all — An oven that does nothing is a different fault. Read the will-not-start page for this brand.
Causes, most likely first on a Hotpoint microwave
- Magnetron at the end of its life — The magnetron makes the heat, and it wears out. The oven runs perfectly in every other respect and simply stops warming anything, often after a period of taking longer and longer. This is a mature platform with a lot of running hours behind it, so the parts that move are the parts that have worn, and they rank first for that reason alone.
- Diode, capacitor or transformer failed — The high-voltage components that feed the magnetron fail as a group and produce the same symptom: everything works except the heat, sometimes with a hum or a buzz that was not there before. This is a mature platform with a lot of running hours behind it, so the parts that move are the parts that have worn, and they rank first for that reason alone.
- Power level, defrost or a timer mode set low — A power level left at its lowest, or a defrost setting, heats so gently that a short test appears to do nothing at all. It is the only free cause on this list, which is exactly why it is checked first. On a long-serving build this ranks below the wear causes, because on a machine this age the moving parts get suspected first for a reason.
Check in this order, and why
- Note whether heating faded over weeks before stopping — A slow fade before total loss is the usual magnetron history. It is first because it is the highest-ranked cause here.
- Note any new hum or buzz that came with the loss of heat — Grouped here because these parts behave alike and none of them are owner-accessible. Second: the next most likely, and free to rule out.
- Reset the power level to full and run a short test — First because it costs nothing and it is embarrassing to skip. Third, and only once the two above are clean.
What an owner can safely check
- Set full power and heat a cup of water for one minute — Water is the honest test load. Never run the oven empty, even briefly.
Tools: a cup of waterAbout 10 min
- Heat a cup of water at full power for one minute and feel it — Water that is clearly warmer means the oven heats and the problem was a setting.
Tools: a cup of waterAbout 10 min
- STOP HERE. Do not open the cabinet of a microwave for any reason — The capacitor inside holds a dangerous charge even unplugged. Owner checks end here.
Before you open anything
Safety
Never remove the outer cabinet of a microwave oven. The high-voltage capacitor inside can hold a lethal charge long after the oven is unplugged, and unplugging it is not enough to make it safe. Never run a microwave empty, because with no load the energy has nowhere to go and the magnetron is damaged within seconds. Never defeat a door interlock for any reason.
When to call a technician
Call once the power level, the outlet and the door have all been checked and the oven still will not warm a cup of water. Call immediately if the breaker trips when the oven should be heating, if you hear arcing, or if you smell burning. Do not open the cabinet while waiting. When you book, say whether the heating faded gradually or stopped all at once: that single detail tells the technician which part to bring.
Nearest pages of this class
What this page does not cover
This page covers Hotpoint microwaves as a class, not one family or model line. Where a family- or model-specific page exists for your unit, that page is the more specific answer and the one to read first. Deliberately not here: wiring colours, torque figures, part numbers and service-manual sequences, 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.
