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Air Conditioning Repairs in Hounslow
Find out what can be fixed yourself, what problems will need an engineer, and if so how quickly we can get to you!
If there is anything wrong with your air conditioning (maybe it's dripping, or stopped cooling altogether) the first thing to think about is whether or not you need a call out. A lot of common faults trace back to simple things, like a dirty filter or a settings mistake.
If you need an engineer, call 020 3143 3147. For non-urgent faults, you can also email us.
- F-Gas certified engineers
- Written price before any work starts
- Units we did not install
Find the fault
Use the fault finder below to narrow down what is wrong.
Need an engineer now? Call 020 3143 3147
Question 1
Common air con faults and what causes them
Most "broken" split systems have a settings, filter, or drain problem, which you can technically fix on your own. However the circuit, electrics, and boards inside these air con units can only be accessed by engineers. This is enforced by law to enforce high safety standards.
| Symptom | Likely causes | Safe owner checks | Engineer if | Typical cost (UK) |
|---|---|---|---|---|
| Running but not cooling | Wrong mode, set temp above room temp, clogged filter, blocked outdoor unit, low refrigerant | Set Cool and below room temp. Clean filters. Clear 30 to 50cm around outdoor unit. | Still weak after filter clean, or ice on pipes | Leak repair and regas £200 to £450 |
| Water dripping from indoor unit | Blocked condensate drain, clogged filter causing coil icing | Clean filter. Check drain hose outlet is not kinked or buried. | Drip continues, or water marks on wall | Drain clear £90 to £180 |
| Ice on pipes or indoor coil | Restricted airflow or low refrigerant | Switch off, let it thaw, clean filter | Ices again within a day | Leak repair and regas £200 to £450 |
| Rattling, buzzing, grinding | Debris in fan, loose panel, failing fan motor or bearings | Check outdoor fan for leaves or debris with power off | Noise from inside the casing | Fan motor £180 to £400 |
| Unit dead, no response to remote | Remote batteries, tripped breaker, failed control board | New batteries. Check isolator and breaker. | Breaker trips again, or no power with breaker on | Control PCB £250 to £450 |
| Short-cycling or wrong temperature | Faulty sensor, oversized unit | Check remote sensor is not in direct sun | Persists after reset | Sensor £120 to £250 |
| Musty smell | Dirty filter or evaporator coil, mould in drain tray | Clean and dry filters fully before refitting | Smell stays after filter clean | Usually covered by a service |
| Error code or flashing lights | Varies by brand and model | Note the code. One power reset at the breaker. | Code returns after one reset | Diagnosis £90 to £150 |
Costs: BestBuilders air conditioning repair cost guide (UK, updated August 2026). Owner checks: Heatable air conditioning troubleshooting. Typical UK ranges, not a quote.
A dirty filter is behind more faults than anything else. Weak cooling, icing, drips, and smells all trace back to it. Cleaning filters takes a few minutes and costs nothing. Try it before you call anyone.
A sealed system should never need topping up. Needing gas means a leak. A regas without a leak repair just buys a few months.
Diagnosis is usually charged first and often credited against the repair. Out-of-hours visits add roughly £80 to £160.
Error codes: what they mean, by brand
Check every code against the manufacturer's own manual before relying on it. Web copies of these lists contradict each other. The table below covers codes we have checked against service manuals for the model ranges listed.
| Brand | Code | Usual meaning | Owner action |
|---|---|---|---|
| Daikin | U4 | Indoor to outdoor communication fault | One reset at the breaker. Engineer if it returns. |
| Daikin | U0 | Refrigerant shortage | Engineer for leak repair. |
| Daikin | A5 | Indoor coil freeze protection | Clean filter, let it thaw. |
| Daikin | E7 | Outdoor fan motor fault (lock) | Clear debris from outdoor fan. Engineer if it returns. |
| Mitsubishi Electric | E6 | Indoor to outdoor communication fault | One reset. Engineer if it returns. |
| Mitsubishi Electric | P4 | Drain or float switch fault | Check condensate drain. |
| Mitsubishi Electric | P8 | Pipe temperature or overheating protection | Clear outdoor unit airflow. Engineer if recurring. |
Daikin: Glow HCE system codes (U4, U0), indoor unit codes (A5), outdoor unit codes (E7) and TechFaultFix Daikin codes. Mitsubishi Electric: Boldr Mitsubishi error codes. Meanings can vary by model.
How to find the code
Display units show it on the indoor panel or wired controller. Most Daikin infrared remotes reveal it by holding the CANCEL or TEMP button until the remote cycles codes and the unit beeps. This varies by remote model, so confirm in your manual. Units without a display flash it as a blink count.
Mitsubishi wall units without a display flash the code. Count blinks of the green OPERATION light and orange TIMER light. A slow steady blink of the operation light alone is standby, not a fault (Boldr blinking light guide).
Other brands
We currently cover Daikin and Mitsubishi Electric in the tool. We are adding Fujitsu, LG, Samsung, Toshiba, and Panasonic as we verify codes against their manuals. If your brand is not listed, call us and we will check.
What an air con repair costs
The cost ranges in the table above are typical UK figures. They come from a regional cost model (BestBuilders repair costs, BestBuilders cost calculator), not invoices, so treat them as guidance.
London rates run 25 to 30 percent above the UK average for installs. Repairs follow a similar pattern. A drain clear that costs £90 to £180 nationally may cost £110 to £225 in Hounslow.
Diagnosis is usually £90 to £150. Many installers credit this against the repair if you proceed. Ask before you book.
Out-of-hours visits add roughly £80 to £160.
One real local figure beats every national range on this page. If you have used an engineer in TW3, TW4, or TW5 recently, we would like to hear what you paid. Email us and we will add it.
Repair or replace?
Repair almost anything on a unit under about eight years old. Parts are available, and efficiency is still close to current models.
| Situation | Steer | Why |
|---|---|---|
| Under 8 years, any fault | Repair | Parts available, efficiency still close |
| Over 8 years, compressor failed (£450 to £900+) | Usually replace | Repair approaches half a new single-room split (£1,500 to £3,000 UK, more in London) |
| Over 8 years, PCB failed (£250 to £450) | Judgement call | Depends on part availability and unit condition |
| Any age, repeated leaks | Find and fix the leak, or replace | Repeated regas is money lost each time |
| Unit runs on R22 | Replace | R22 cannot legally be used to service systems, so any repair that removes the gas cannot be refilled |
Repair and replacement costs: BestBuilders repair costs and BestBuilders split system costs. R22: Cooling Post.
Before you call anyone, find the refrigerant type and install year on the outdoor unit's rating plate. This answers the repair-or-replace question faster than anything else.
Replacing? Work out the right unit with the air conditioning size calculator, compare system types, and see replacement costs by West London borough.
How a repair visit works
- Call or emailJust get in touch and tell us the brand, the symptom or error code you are seeing. It's also very helpful if you can tell us roughly how old the unit is.
- DiagnosisWe'll pop by, find the fault, and give you a price quote before you decide to proceed.
- RepairWe'll get your unit up and running again, but also take care of whatever caused the problem in the first place (that way it won't come up again!)
- F-Gas recordWe update the F-Gas record for your system if applicable.
- Follow-upIf the fault returns within the warranty period, we come back.
We are also more than happy to repair units we didn't personally install. If you bought a system from another installer, we can still sort it for you.
An annual service catches drain, filter and leak problems early. See air conditioning servicing.
Areas covered and contact
We cover Hounslow and the surrounding TW postcodes, including TW3, TW4, TW5, and TW6. We also cover West London more widely.
For non-urgent faults, email us with your brand, model, symptom or error code, and the unit's age. We will respond with next steps.