Air conditioning
not cooling
It is running, the fan is turning, and the air coming out is not cold. That is one of five things, and two of them you can rule out yourself in ten minutes without paying anybody.
- 89 pounds plus VAT to diagnose, waived if we do the repair
- Any make and any age, including other installers' systems
- We will tell you when a repair is not worth doing
Brands we work with
Air conditioning that runs but does not cool is most often a refrigerant leak, a blocked filter, a dirty outdoor coil, a failed capacitor or a system left in the wrong mode. A diagnosis is 89 pounds plus VAT, waived if we do the repair, and the commonest fix costs 400 to 700 pounds.
Do the two free checks below before you book anyone, including us. One of them fixes this more often than any paid repair does.
Two things to check first, because they are free
The mode, and this is not condescending
A heat pump air conditioner has a heating mode, a drying mode and a fan-only mode, and the remote is easy to knock. Fan-only turns the fan on and the compressor off, which is exactly what “running but not cold” feels like. Put it on Cool, set the target to 18, and give it ten minutes. If cold air arrives, that was it.
The filters
Open the front of the indoor unit and slide them out. If they are grey, wash them in warm water, dry them completely and put them back. A blocked filter starves the coil of air, which drops the output and eventually ices the coil up. It is the single most common reason a system stops cooling and it costs nothing to rule out.
The five real causes, in the order we find them
| What it is | Why it happens | Typical cost |
|---|---|---|
| Refrigerant leak | Cools weakly, then not at all. Often ice on the thin copper pipe at the outdoor unit. | £400 to £700 with recharge |
| Blocked filters or indoor coil | Weak airflow, sometimes a smell, sometimes ice on the indoor coil. | £95 service, or £160 deep clean |
| Dirty or blocked outdoor coil | Cools fine in the morning and gives up in the afternoon heat. | £95 service |
| Failed capacitor or contactor | Outdoor fan spins but the compressor never starts, or it hums and stops. | £120 to £280 |
| Failed compressor | Nothing from the outdoor unit at all, or it trips the breaker on start. | £900 to £1,600, usually replace instead |
Prices include labour. VAT is extra. If the fault should still be under manufacturer warranty we will tell you and help you claim rather than charging you for it. Every figure on this site is an estimate based on published UK market ranges and our own installation experience. It is not a quotation. The price you are given after the free survey is the price you pay.
Why a refrigerant leak is the most likely answer
A split system is a sealed circuit. It does not consume refrigerant, so if there is less in it than there was, it went somewhere. The commonest place is a flare joint at the outdoor unit that was not torqued correctly at installation, and the second commonest is vibration fatigue where the pipe leaves the wall unsupported.
The tell is gradual. A system that cooled well last summer, adequately in June and not at all in August has been losing charge all along. A system that stopped dead overnight is more likely electrical.
Topping it up without finding the leak is not a repair, it is a way of selling the same refrigerant twice. Anybody who offers to just regas it and leaves is planning on you calling back.
When we will tell you to replace it instead
A failed compressor on a system over ten years old. The repair is 900 to 1,600 pounds on a machine near the end of its life, and a new system is 1,750 to 3,500 pounds with a fresh manufacturer warranty and materially lower running costs.
An R22 system. R22 has been banned for servicing since 2015, so it cannot legally be topped up. Any refrigerant fault on an R22 system means replacement, and the tell is usually an installation date before about 2004.
Repeated leaks on the same joint set. At the third one the pipework is the problem, not the joint.
What happens when you call us
- You describe the symptom. Half the time that is enough for us to tell you the likely cause and the likely cost before anyone travels.
- We attend and diagnose properly, with instruments rather than by guessing. That is 89 pounds plus VAT.
- You get the cause, the price and an honest answer on whether it is worth repairing, before anything is touched.
- If you go ahead on the same visit, the diagnosis charge comes off.
Other faults
Leaking water
Water down the wall from the indoor unit. Nearly always the drain.
Leaking waterMaking a noise
What each noise means, and what to do when a neighbour complains.
Making a noiseShowing a code
Verified Daikin and Mitsubishi fault codes, and what each family costs.
Showing a codeRelated
All air conditioning repairs
Every symptom, cause and price in one table, plus when replacing beats repairing.
RepairsAnnual servicing
95 pounds plus VAT. The one thing that prevents most of the faults on this page.
Book a serviceReplacement cost
What a new system costs, for when the repair stops making sense.
See pricesQuestions people ask about this
Why is my air conditioning blowing warm air?
If the air is actually warm rather than just not cold, the most likely answer is that the unit is in heating mode, which on a heat pump is one button away from cooling. Check the remote reads Cool and not Heat or Auto before anything else.
If it is genuinely on Cool and the air is warm, the compressor is not running. That is a capacitor, a contactor, a pressure switch that has cut out on low charge, or the compressor itself, and it needs a meter rather than a guess.
How much does it cost to find out what is wrong?
89 pounds plus VAT for a full diagnosis, and it is waived entirely if you go ahead with the repair on the same visit. You get the reading, the cause and a price before anyone touches anything.
Can I just get it regassed?
Not honestly, no. A sealed circuit that has lost refrigerant has a leak, and putting more gas into it without finding the leak means you are paying for the same repair again next season. We find the leak first and quote the repair with the recharge in it.
There is also a legal side: refrigerant cannot simply be released or topped up without the correct handling, and on an R22 system it cannot be done at all.
It cools in the morning but not in the afternoon. Why?
Almost always the outdoor unit. Its job is to reject heat, and it can only do that if air moves freely through the coil. When the coil is furred with dust, pollen or cut grass, or something has been stacked against it, it copes at 20 degrees and fails at 30.
Clear a metre of space around it and look at the fins. If you cannot see daylight through them, that is your answer, and a 95 pound service will fix it.
How quickly can you come out?
In north London, usually the same or the next working day in season. Further out it depends on what is booked, and we will give you the honest date rather than the one that gets the job.
Tell us the symptom
Describe what it is doing and we will tell you the likely cause and a realistic price before we come out. Diagnosis is 89 pounds plus VAT and it comes off the repair.
Monday to Friday 9am to 7pm, Saturday 10am to 3pm, Sunday closed
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