Air conditioning maintenance checklist: keep your AC running for years
A well-maintained air conditioning unit can run efficiently for 12–15 years. A neglected one can lose 5% efficiency per year, start smelling, and fail just when you need it most. Here's the maintenance checklist we give customers after every install.
Monthly jobs (five minutes each)
- Wipe the indoor unit casing with a soft, damp cloth — dust blocks airflow and can smell.
- Check the filters. If they're grey or fuzzy, remove and wash them in warm soapy water.
- Make sure nothing is blocking the indoor unit's air intake (curtains, furniture, toys).
- Check the outdoor unit for leaves, grass clippings, or debris. Clear a 30cm space around it.
- Run the unit in 'heat' mode for 20 minutes, even in summer. This keeps the reversing valve and compressor seals healthy.
Annual jobs (or book a service)
- Deep clean the indoor coil and drain pan — this is where smells and blockages start.
- Flush the condensate drain to prevent leaks and water damage.
- Check the outdoor coil for dirt buildup and clean it gently with a soft brush or fin comb.
- Check pipe insulation is intact; missing insulation wastes energy and causes condensation.
- Test refrigerant pressures and look for leaks — only an F-Gas engineer can do this legally.
- Check electrical connections, isolator, and fused spur for safety.
DIY vs professional service
| Task | You can do | Needs an engineer |
|---|---|---|
| Filter cleaning | Yes | No |
| Outdoor unit clear of debris | Yes | No |
| Indoor coil deep clean | No | Yes |
| Refrigerant leak check | No | Yes (F-Gas legal requirement) |
| Electrical safety check | No | Yes |
| Drain flush and test | Preferably no | Yes |
What a professional service costs
For a single domestic split unit, a proper annual service is typically £90–£140. Multi-split systems with 2–5 indoor units are £150–£220. That's much cheaper than a mid-summer breakdown callout, which can be £180–£300 before parts.
Signs your unit needs attention now
- Musty or sour smell — bacteria or mould in the drain pan or coil
- Water leaking inside — blocked condensate drain
- Blowing warm on cooling mode — low refrigerant, dirty filters, or outdoor coil blocked
- Loud rattling or vibration — loose panel, fan issue, or mounting problem
- Higher electricity bills than last year — often dirty filters or coils working harder
FAQ
How often should domestic air conditioning be serviced?
At least once a year. If you use it for heating and cooling year-round, or have pets and dust, twice a year is better.
Can I clean my AC filters myself?
Yes — most slide out from the bottom of the indoor unit. Wash in warm soapy water, dry completely, then slide back in.
Why does my air conditioning smell?
Smells usually come from mould or bacteria in the indoor coil or drain pan. A deep clean and drain treatment fixes it.
Is an annual service plan worth it?
Yes for most households. It spreads the cost, includes priority callouts, and keeps the warranty valid.
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