Not cooling, leaking water, tripping the breaker? Most faults are £100–£450 fixes. Check the free stuff below first — then we'll match you with an independent local F-Gas engineer.
Filters. Pop the indoor unit's cover, slide the filters out. Grey felt = your fault found; rinse, dry, refit. Clogged filters cause half of "not cooling" calls.
The remote. Confirm mode is cooling (snowflake), not fan or dry, and the setpoint is below room temperature. It sounds insulting; it resolves a shameful number of call-outs.
The breaker. Check the consumer unit for a tripped circuit. Trips once, fine; trips repeatedly, stop resetting it and book the engineer — something's genuinely wrong.
Still broken? That's a real fault. Here's what fixes cost:
For step-by-step symptom guidance covering warm air, leaks, smells, noise, power and icing, use the complete air conditioning not working fault finder.
Smoke, sparks, repeated breaker trips, water near electrics or a heat-related health risk need a different response. Start with the UK emergency repair and safety guide.
| Symptom | Likely cause | Typical repair cost |
|---|---|---|
| Weak or warm airflow | Dirty coil, failing fan motor, low refrigerant | £100–£350 |
| Water dripping indoors | Blocked condensate drain | £90–£180 |
| Ice on the indoor unit | Airflow starvation or refrigerant leak | £150–£450 (leak find + fix + re-gas) |
| Won't turn on | Capacitor, PCB, sensor | £120–£400 |
| Loud grinding / rattling outside | Fan motor or compressor bearings | £150–£1,200 depending which |
| Breaker trips on start | Compressor or wiring fault | £200–£1,200 — diagnosis first |
Anything touching refrigerant legally needs an F-Gas certified engineer — and beware the £80 "top-up" that ignores the leak; gas doesn't get used up, it escapes, and it'll escape again.
Decision tool
Compare the repair against replacement cost, equipment age, warranty, efficiency and recent fault history. The result shows which facts deserve more weight—it does not replace a diagnosis.
Instant result · no email requiredThis is a budgeting decision aid, not an engineering verdict. Safety faults, refrigerant leaks and compressor diagnoses require a qualified local technician.
Repair normally wins when the system is young, parts remain supported and the fault is isolated. Ask for the diagnosis, part number, labour, repair warranty and whether any other major components tested weak. A £250 drain or sensor repair should not become a replacement sale simply because the engineer is already on site.
Get a replacement comparison when the compressor or coil has failed, major parts are obsolete, the system has repeated expensive faults, or the repair is a large share of a correctly sized new installation. For older R22 equipment, adding or using R22 for servicing is prohibited; ask whether a compliant conversion is technically and economically sensible or whether replacement is the better route. Do not use an arbitrary age-times-price formula in place of those facts.
Most July breakdowns announce themselves in spring: weak airflow, odd smells, slow drips. An annual service at £60–£120 catches them while parts are cheap and engineers are available — not in week two of a heatwave queue.
A diagnostic call-out typically runs £90–£150, often waived or absorbed if you go ahead with the repair. Common fixes land £100–£450: sensors, capacitors, fan motors, drain blockages and re-gassing after a leak repair. Compressor failure is the expensive one — £600–£1,200+ — and on older units usually triggers the replace-instead conversation.
The usual suspects in order: filthy filters choking airflow (check first — two minutes, free), a remote accidentally set to fan or dry mode, a tripped breaker, iced-up indoor coil, or low refrigerant from a slow leak. The first three you can fix yourself; ice and refrigerant need an F-Gas engineer — topping up gas without fixing the leak just rents you a few cool weeks.
Almost always a blocked condensate drain: the moisture your unit wrings from the air can no longer run outside, so it drips from the indoor unit. An engineer clears and flushes the line in a short visit; between visits, dust filters regularly — most blockages start as dust washed into the drain pan.
Anything touching the refrigerant circuit — leaks, re-gassing, coil or compressor work — legally requires F-Gas certification in the UK. Electrical faults and drain blockages don't, strictly, but an F-Gas firm can handle whatever the diagnosis turns out to be, which is why we only pass repair enquiries to certified businesses.
Repair usually makes sense for a younger system with an isolated, warrantied fault. Compare replacement when a compressor or coil has failed, parts are obsolete, the unit has repeated major faults, or the repair is a large share of a correctly sized new installation. Ask for both written prices, remaining warranties and expected lead times rather than using an arbitrary age formula.
Outside heatwaves, most local firms diagnose within a few working days. During heatwaves everyone's queue explodes — another argument for an annual service, which catches most July breakdowns in April.
Tell us what has gone wrong. We match you with an independent local specialist who calls to confirm the fault, access and next diagnostic step before quoting. It costs nothing either way.
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Free planning tools
Use a cooling or heating estimate to prepare for a properly surveyed installer quote.