You can handle the most important air conditioner maintenance tasks yourself. Clean the filter you can reach, keep airflow clear and watch for leaks. There’s no need to take the unit apart. Leave internal cleaning, electrical repairs and refrigerant work to a qualified professional.
Here’s a practical routine for split and portable units. Start with your model’s manual, since filters, drain setups and safe cleaning steps can vary.
Your maintenance routine at a glance
These are checkpoints, not a replacement for your manual’s instructions. Dust, pets and how often you use your AC can affect how often you need to do maintenance.
| When | What you can do | Professional task |
|---|---|---|
| Every few weeks in heavy use | Check and clean accessible filters as your manual directs. | — |
| Monthly during use | Look for blocked airflow, leaks and unusual noise; clear loose leaves outside. | Investigate anything that persists. |
| Before a cooling season | Test cooling, check the window kit or outdoor unit and review the manual. | Book a service if one is due. |
| Usually annually for a split | — | Service according to the manufacturer’s schedule and warranty terms. |
| Before storing a portable unit | Drain and dry it as the manual directs. | Repair leaks or faults. |
How do you clean an indoor filter?
When: Check the filter every few weeks if you use your AC a lot. For example, one Daikin split-system manual suggests cleaning every two weeks, but your model might be different. If you have pets or notice weaker airflow, check it sooner. Clean or replace the filter as your manual recommends.
How: Turn off the AC. Open the access panel as shown in your manual, unclip the filter and vacuum off any loose dust. If your manual allows it, rinse or wash the filter, let it dry completely in the shade and put it back before turning the AC on. Replace disposable or damaged filters with the correct part. Never run the unit without a filter.
Many wall-mounted split units use washable mesh filters, so the usual advice to replace filters every three months may not apply. If airflow is still weak after cleaning, ask an installer to check it instead of opening the unit yourself.
How do you look after an outdoor unit?
When: Take a quick look at the outdoor unit about once a month while you’re using the system, especially after gardening or windy days. Check it again before summer starts.
How: Turn off the system, then pick up loose leaves, remove items stored near the unit and trim plants that block the air inlet or outlet. Check for visible dirt or damage, but don’t remove the grille. Your manual will tell you the right clearances; there’s no one-size-fits-all rule.
Some manufacturers allow a gentle hose rinse of the outdoor coil. Daikin describes this for its outdoor unit, but follow your manual before using water. Never use a pressure washer or spray electrical covers. If access requires a ladder, or the fins are heavily clogged or bent, leave cleaning to a technician.
What should you check for water leaks?
When: Look under the indoor unit while it’s cooling and watch for drips, musty smells or unexpected water stains. Portable units might also show a full-tank warning.
What to do: If you see water dripping inside, turn off the system and check the basics: a dirty filter you can reach or a full tank in a portable unit. Follow your manual’s instructions for emptying the tank. If water keeps coming back or the split unit’s drain looks blocked, call an installer. Ask them to check the tray, pipe and any condensate pump.
Don’t pour vinegar or bleach into a wall unit as part of your routine. Drain designs differ, and adding chemicals can cause new problems. Don’t spray cleaner into the indoor coil or take the case apart to reach it.
What happens during a professional service?
When: Follow your manufacturer’s recommended schedule and check your warranty terms. Daikin, for example, suggests an annual service by a qualified engineer for its air-to-air systems. Booking before summer can be a good idea, so arrange it in advance.
What to ask for: Ask the technician to check airflow and filters, clean internal parts if needed, check the condensate drain, test the cooling and controls, and inspect electrical parts. Find out what they checked, what they cleaned and whether any repairs are needed. If your AC keeps losing cooling performance, ask them to investigate the cause. Refrigerant shouldn’t need topping up like fuel.
UK rules require appropriate qualifications for work on equipment containing F-gas. A typical wall-mounted domestic split does not have a blower belt for you to lubricate, so avoid generic service checklists written for ducted systems.
When should you call before the next service?
Don’t wait for your annual service if the unit leaks inside, ices up, trips a breaker, smells burnt, makes grinding noises or keeps showing an error. Turn it off right away if you see water near electrical parts or smell something burning. Then call a professional to check it.
If your AC isn’t cooling as well, clean the filter and make sure windows are closed and air paths are clear. If that doesn’t fix it, let your installer know when the problem started and what you’ve already tried. Frequent starting and stopping can have several causes, including a unit that is too powerful for the room. Our guide to an air conditioner that is too big for a room explains short cycling in more detail.
If the unit runs but no longer cools, use our running-but-not-cooling checklist for the first safe checks.
How do you maintain a portable AC?
Every few weeks during use: Check the filter as your manual directs. Make sure the exhaust hose isn’t crushed and the window kit still seals properly. Empty the tank when your model tells you to. Some units evaporate most of the water while cooling but may still need draining in certain conditions.
Before storage: Follow the manufacturer’s drain and drying procedure, clean the filter and store the hose without sharp bends. If the machine leaks or still cools poorly after these checks, contact the manufacturer or a repairer. Leave the sealed refrigerant circuit alone.
Does maintenance change running costs?
A clean filter and unobstructed airflow help the AC cool as intended. How much money that saves depends on how dirty it was, the room and how you use the system.
If you already own an AC, CostToCool’s free Calculate my current setup tool estimates running costs based on your room, unit and schedule. If you are planning a replacement, the free Plan cooling for my home tool estimates a capacity range and possible costs. Both give estimates, not fault diagnoses.