Swan microwave humming but not heating?
Hoping someone can help with my Swan microwave (SM22070BN) — loud hum and no heat, which I've read points to the magnetron. Grateful for any pointers, thanks.
Solution Summary
AI-generated from this discussion
This thread was marked as solved. Here's a summary of the problem and the fix, generated from the discussion below.
Swan SM22070BN microwave hums loudly but does not heat
- The problem
- A Swan microwave, model SM22070BN, was reported to run with a loud/deeper hum but produce no heat.
- Likely cause
- The accepted reply says this symptom strongly suggests a fault in the high-voltage circuit. Possible causes mentioned were the magnetron, high-voltage diode, capacitor or transformer. The exact failed part was not confirmed.
- What fixed it
- No repair was confirmed in the discussion. The accepted advice was not to replace parts by guesswork and to have the microwave professionally diagnosed, as internal high-voltage components can retain a dangerous charge and similar symptoms can be caused by several parts. Repair may be uneconomical depending on the appliance's age and value.
- Checks to try
- Heat a mug of cold water for 1 minute to confirm whether the turntable, light and fan run while the water stays cold and the hum is louder/deeper than usual.
- Check for any burning smell, arcing, or scorching inside the cavity or around the waveguide cover.
- Parts or tools mentioned
- magnetron
- high-voltage diode
- high-voltage capacitor
- transformer
Safety: Do not attempt internal microwave repairs unless properly trained. Further diagnosis should be carried out by a suitably qualified appliance engineer.
1 Answer
A loud hum with no heating often does point to a fault in the high-voltage side of the microwave, but it is not always the magnetron itself. On these, the capacitor, diode, transformer or magnetron can all give similar symptoms.
Before doing anything, isolate the microwave from the mains. Microwaves contain a high-voltage capacitor that can retain a dangerous charge even when unplugged, so internal checks are not suitable unless you are properly trained.
A few sensible checks:
1. Confirm the symptom clearly Heat a mug of cold water for 1 minute. If the turntable, light and fan all run normally but the water stays cold while the unit gives a deeper/louder hum than usual, that does strongly suggest a high-voltage circuit fault.
2. Check for burning smells or visible damage If there has been any burning smell, arcing, or scorching inside the cavity or around the waveguide cover, stop using it. That can indicate a different fault from a simple magnetron failure.
3. Consider the age and value of the appliance On many Swan countertop models, repair can be uneconomical once the fault is in the high-voltage section, especially if labour is involved.
4. Do not replace parts by guesswork A magnetron is a common suspect, but the HV diode and capacitor are cheaper parts and can also cause no-heat/humming faults. Proper diagnosis needs safe testing procedures.
Because this involves mains and high-voltage components, I’d recommend a qualified microwave engineer rather than DIY internal repair. If you want, I can help you decide whether it’s likely worth repairing based on the microwave’s age and condition.
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This answer was generated automatically by the WhitegoodsHelp AI Assistant. It is not provided by an engineer or any other qualified person, may be inaccurate or incomplete, and is not professional or technical advice. Do not rely on it. Always use your own judgement and consult a qualified engineer before carrying out any electrical, gas or water work. Use is entirely at your own risk. See our full Terms of Use.
SAFETY FIRST: READ BEFORE ACTING ON THIS GUIDANCE
Never work on a live appliance
Always unplug it at the mains before going near it with any tools.
Never attempt gas work
By law, gas appliances must only be worked on by a Gas Safe registered engineer. If your fault involves gas, stop and call a professional. Do not attempt it yourself.
Watch for sharp edges
Outer panels are smooth, but internal parts have sharp machined edges. Wear protective gloves and arm sleeves.
Water appliances can leak
Turn off the water supply before disconnecting any hoses.
Know your limits
If you are not confident testing or working inside the appliance, stop and call a professional.
AI guidance, not guaranteed
This response is generated automatically by the WhitegoodsHelp AI Assistant. It is not professional or technical advice, may be incomplete or wrong, and must not be relied upon. Always use your own judgement and consult a qualified engineer before any electrical, gas or water work.
This is general information only and is not professional advice. The WhitegoodsHelp AI Assistant is not an engineer and is not qualified. See our full Terms of Use.
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