The short answer
A service is a clean and check of the whole system, indoors and out, plus tests of how it runs and a look for leaks and wear. Manufacturers typically recommend one regularly, often once a year.
On this page
Cleaning the filters keeps air moving, but the parts behind them collect dirt too, and a slow leak or a worn part rarely shows from the front of the unit. A service deals with the parts you can't safely reach yourself. What's included varies between engineers, so ask for a list of the checks before you book.
How often, and whether you have to
Manufacturers typically recommend regular servicing, often once a year, and some warranties depend on it. Check the terms of yours, and keep the paperwork from every visit.
A system that heats through the winter and cools through the summer runs far more hours than one used on a few hot days, and one in a kitchen or a dusty room gets dirty faster. Either may need attention more often, and an engineer can advise after the first visit. Booking ahead of the season you rely on it most leaves time to fix anything the service finds.
For a typical home system, servicing is recommended rather than required by law. Mandatory leak checks apply only to systems whose refrigerant adds up to 5 tonnes CO2-equivalent or more, and a home split holding roughly 0.5–1.5 kg of R32 is far below that. F-gas rules for homeowners explains the rules in more detail.
What the engineer checks
A thorough service usually covers the following, though the exact list varies.
| Part | Typical checks |
|---|---|
| Filters | Cleaned and checked for damage |
| Indoor coil | Cleaned, fins checked |
| Indoor fan | Cleaned, checked for wear |
| Drain | Tray and pipe flushed, pump tested if fitted |
| Outdoor unit | Debris cleared, coil cleaned, fan checked |
| Fixings | Brackets or stand, feet and casing secure |
| Pipework | Insulation, covers and joints inspected |
| Electrics | Connections and isolator checked |
| Performance | Each mode run, air temperatures measured |
Indoors, the coil and the long, drum-shaped fan behind the louvres gather the dust that gets past the filters. Engineers often clean them in place, with a waterproof cover hung under the unit to catch the run-off. Some also offer a deeper clean in which the fan or drain tray is taken out, so ask which one you're getting.
The performance check compares the temperature of the air going into the unit with the air coming out, in cooling and in heating. Some systems also keep a record of past faults that the engineer can read. A good engineer looks for early signs of trouble too: oily marks at pipe joints, frost where there shouldn't be any, corrosion, or a fan that is starting to sound rough.
Refrigerant and top-ups
The refrigerant in a split system circulates in a sealed circuit and isn't used up. If there's less than there should be, it has usually leaked, although the amount can also have been wrong since installation. The right fix is to find and repair any leak before adding more. A top-up without a search for the leak only puts off the problem, because the new refrigerant escapes too.
Some engineers only connect gauges to the refrigerant circuit when the temperature readings suggest a problem, because each connection can lose a little refrigerant. Anyone who works on the circuit needs the right F-gas qualification, and the business needs a company F-gas certificate.
Getting ready for the visit
- Clear a space below each indoor unit for a step ladder and a drip cover, and move or cover anything underneath.
- Make sure the engineer can reach the outdoor unit: the side gate open, a clear path, and a warning in advance if it's high on a wall.
- Find the model numbers, the installation date and any earlier service records.
- Write down anything you've noticed, such as drips, smells, new noises, error codes or a room that doesn't reach temperature.
A service on a single wall unit often takes around an hour. A multi-split, or a deeper clean, takes longer.
What you should get afterwards
Ask for a written record of the visit: the date, what was cleaned and checked, the readings taken, anything that needs attention, and the engineer's details. Keep it with the installation and commissioning paperwork. It supports warranty claims, lets the next engineer spot changes over time, and is useful if you sell your home.
If the service turns up a fault, you should get a clear explanation of what it is, what fixing it involves and whether the system is safe to use in the meantime. For problems that come up between services, see when to call an engineer.
Related guides
- How to clean the filtersSwitch the unit off, lift the front panel and take out the mesh filters, then vacuum or rinse them in lukewarm water and let them dry fully before refitting. In regular use, this usually needs doing every few weeks.
- When to call an engineerCall an engineer when simple checks don't fix a problem, and switch off straight away for burning smells, smoke, a circuit breaker that keeps tripping or signs of a refrigerant leak. Refrigerant, electrics and anything inside the casing are work for a qualified engineer.
- F-gas rules for homeownersF-gas rules in Great Britain require anyone installing, servicing or removing a split system to hold the right qualification, and ban releasing refrigerant. A typical home system is well below the size that needs mandatory leak checks.
- How long air conditioning lastsA well-installed, regularly serviced wall-mounted system typically lasts around 10 to 15 years, and some keep going longer. How long yours lasts depends on installation quality, how hard it works, where the outdoor unit sits and how it's looked after.