Fault-finding first, parts second
Air conditioning faults tend to show up when you need the system most: the first hot week of summer, or the first cold snap when you switch to heating. Guessing and swapping parts rarely gets you there. The quickest lasting fix comes from working out exactly why the system is misbehaving. A unit that is not cooling might have a clogged filter, a failed fan capacitor, a faulty sensor or a refrigerant leak, and each needs a completely different repair.
We repair air-to-air systems in homes, offices, shops and other commercial premises across York and the surrounding area, including wall-mounted splits, multi-splits, ceiling cassettes, ducted units and floor consoles, whoever installed them. We’ll ask what you’ve noticed, test the system properly and tell you the cause in plain English. Nothing gets done until you’ve agreed to it.
Home systems
Bedroom units that have stopped cooling, living room systems that leak, and heat pumps that will not heat as the weather turns.
Offices and server rooms
Meeting rooms that have become unbearable, zones that ignore their controller, or a comms room unit that has tripped. See office air conditioning.
Shops, salons and restaurants
Systems under heavy load where a fault quickly affects customers and staff, and repairs need planning around trading.
Landlords and inherited systems
Tenant-reported faults, and units that came with a property with no service history or paperwork.
Common air con faults at a glance: symptoms, causes and next steps
This table should help you narrow it down. The middle columns are the most likely causes, roughly in order of how often they turn up, and what you can safely try yourself. Anything in the last column needs a qualified engineer.
| Symptom | Likely causes | Safe to try yourself | Needs an engineer |
|---|---|---|---|
| Running but not cooling | Wrong mode or set point, clogged filters, blocked outdoor unit, low refrigerant, failed fan or sensor | Check mode is Cool, lower set point, clean filters, clear around outdoor unit | Refrigerant checks, fan motors, sensors, compressor faults |
| Water dripping indoors | Blocked drain, lost fall, failed condensate pump, dirty coil, iced coil thawing | Switch off, protect below, clean filters | Clearing and re-routing drains, pump replacement, coil cleaning |
| Ice on pipes or coil | Restricted airflow, low refrigerant, faulty fan or sensor | Switch off and let it thaw, clean filters | Leak detection, repairs and recharge |
| Musty or damp smell | Mould or biofilm on coil, fan or drain tray; standing water | Clean filters; run Fan or Dry mode to dry out | Deep clean of coil, fan barrel and tray |
| Rattling, buzzing or squealing | Loose panels, debris, worn fan bearings, failing capacitor, vibration | Clear debris around outdoor unit from a safe distance | Fan motors, bearings, capacitors, mountings |
| Will not start or trips breaker | Tripped isolator, control fault, electrical fault, compressor or PCB failure | Check controller batteries; reset breaker once only | Any repeated tripping or electrical fault |
| Error code or flashing light | Sensor, communication, pressure, fan or drain faults | Note the code; power off for a few minutes and restart once | Diagnosis and repair of the reported fault |
Stop and switch off if…
you notice a burning smell, scorching or melting around either unit, sparking, or a breaker that trips again after one reset. Switch off at the isolator, do not keep resetting it, and call an engineer.
Why is my air conditioner blowing warm air?
Most often the cause is a setting, a clogged filter or a blocked outdoor unit, but it can also be low refrigerant from a leak, a failed fan or a faulty sensor. Rule out the simple stuff first. If nothing changes, call an engineer.
Settings, modes and controllers
Check the controller is set to Cool (snowflake) or Heat (sun), not Fan, Dry or Auto, and that the set point is genuinely below room temperature for cooling. Weak remote batteries, a lost pairing or a timer you forgot about can all look like a fault. Wall controllers on commercial systems may be locked out or overridden by a central controller.
Airflow problems indoors and out
A heavily clogged filter starves the indoor coil of air, cutting output and sometimes causing ice to form. Outdoors, leaves, plants, garden furniture or a cover left on after winter stop the condenser rejecting heat, so the system struggles and may cut out on high-pressure protection. Dirty coils have a similar effect over time.
Refrigerant, compressor and electronic faults
If airflow is fine and the system still underperforms, the cause is usually in the refrigerant circuit or electronics.
Signs pointing to the refrigerant circuit
- Gradual loss of cooling over weeks or months
- Frost on the smaller pipe at the outdoor unit or on the indoor coil
- Oily marks at flare joints or along the pipework
- The outdoor unit runs but the air from the indoor unit is barely cooler than the room
Signs pointing to electrical or control parts
- Outdoor fan not turning while the compressor hums
- System starts then stops after a few minutes
- Error codes relating to sensors, communication or the inverter
- Indoor unit lights up but the outdoor unit never starts
Why is my air conditioner leaking water?
An indoor unit drips when condensate cannot drain away as designed, most commonly because the drain is blocked, has lost its fall or the condensate pump has failed. Every air conditioner removes moisture from the air when it cools; that water collects in a tray under the coil and should run away through the drain without you ever seeing it.
Blocked or badly routed drains
Dust, slime and biological growth build up in the drain tray and pipe, particularly if filters have not been cleaned. A drain that sags, rises, has been squashed behind trunking or has its outlet blocked by leaves or ice will back up and overflow. The fix is to clear and flush the drain and, where the route itself is the problem, re-run it with a continuous fall.
Condensate pump failures
Where water cannot drain by gravity, a small pump lifts it away. Pumps can fail, block or lose power, and their float switches can stick.
How to tell the pump is struggling
- A new gurgling, buzzing or constant running noise from the pump
- The unit cuts out, sometimes with a drain-related error code, if the safety switch trips
- Water appearing intermittently during humid weather
Is water dripping from the outdoor unit normal?
Yes, in heating mode it usually is. The outdoor coil gets cold and collects moisture, and in winter it periodically runs a defrost cycle that releases water and sometimes a puff of steam. So water round the outdoor unit in cold weather is fine, though it can freeze on paths, so think about where it runs. Ice that builds up on the outdoor unit and never clears is a different matter.
While you wait for a repair
Switch the unit off, put a towel or container below it and keep electrical items away. Clean the filters if you can do so safely, as a heavily iced coil thawing out can look like a drain fault.
Noises, smells and ice: other warning signs worth acting on
- Rattling or vibration
- Loose panels or screws, debris in the outdoor fan, or a unit no longer sitting firmly on its anti-vibration mounts.
- Squealing or grinding
- Often worn fan motor bearings. Worth dealing with before the motor fails completely.
- Buzzing or humming without starting
- Can indicate a failing capacitor or contactor, or a compressor struggling to start. Switch off and call an engineer.
- Clicking or cracking
- Plastic casings expanding and contracting as temperatures change is normal; repeated clicking with no start-up suggests a control fault.
- Hissing
- Refrigerant changing state is normal at start-up and during defrost; a constant hiss near pipework could be a leak.
- Musty or sour smell
- Mould or bacterial growth on the coil, fan barrel or drain tray, usually from standing water and dirty filters.
- Burning or electrical smell
- Switch off at the isolator immediately and get the system checked.
Ice on the indoor coil or pipework usually means air is not flowing over the coil properly or refrigerant is low. Switch the system off and let it thaw fully. Don’t keep it running in the hope it clears, because that can let liquid refrigerant reach the compressor. Blocked filters are the usual culprit, and they’re the first thing we look at on every routine service.
Making sense of error codes and flashing lights
An error code is the system telling you which protection or sensor has tripped. Codes are specific to each manufacturer and often to each model range, so the same code can mean different things on different units. The code gives an engineer a starting point. It still takes testing to find the root cause, especially on commercial systems where several indoor units share one outdoor unit and long control cables.
Typical categories of fault code
- Sensor (thermistor) faults: a temperature sensor reading out of range, often from a failed sensor or a loose plug.
- Communication errors: indoor and outdoor units not talking, from wiring faults, a failed board or power issues.
- Pressure or temperature protection: the system shut itself down because pressures or temperatures went outside safe limits, often from airflow problems or refrigerant issues.
- Fan motor faults: the indoor or outdoor fan not reaching the expected speed.
- Drain or float switch alarms: water backing up in the tray or pump.
- Inverter or compressor faults: problems with the power electronics or the compressor itself.
What to note before you call
- The exact code or the number of flashes and which light is flashing
- The make and model, from the label on the side of the indoor or outdoor unit
- When the problem started and whether it is constant or intermittent
- Whether it happens in cooling, heating or both
- Photos of both units, the controller display and any visible damage or water
Refrigerant leaks: finding them, fixing them, and the rules
Refrigerant doesn’t get used up like fuel. It goes round a sealed circuit, so if the charge is low, there’s a leak somewhere. Topping it up and walking away just means you’ll be calling someone again in a few months, and the gas that escaped is bad for the environment.
How do engineers find a refrigerant leak?
- Inspect flare joints, service valves and pipework for oily residue, which often marks the spot.
- Use an electronic leak detector around joints, coils and valves while the system is running.
- Apply leak-detection solution to suspect joints and watch for bubbles.
- Where the leak is elusive, recover the refrigerant and pressure test sections of the circuit with nitrogen to isolate it.
Repair, test and recharge
Once found, the leak is repaired, for example by remaking a flare, brazing a joint or replacing a damaged coil or pipe section. The circuit is then pressure tested, evacuated to a deep vacuum and recharged with the correct weight of refrigerant. A follow-up check to confirm the repair has held is good practice, and for larger systems above certain charge thresholds periodic leak checks are a legal requirement. That’s one reason businesses with bigger systems tend to put them on a planned maintenance schedule.
F-Gas rules apply to every refrigerant repair
Under UK F-Gas rules, anyone installing, servicing or repairing equipment containing fluorinated refrigerant must hold the appropriate F-Gas certification. Refrigerant must be recovered properly, never vented. Whoever you call, ask to see their certification before they open up the refrigerant circuit.
Repair or replace? Weighing up an ageing system
Most faults on a reasonably modern system are worth repairing: drains, fans, sensors, capacitors and leaks at joints are all routine. It gets harder when a major part fails on an older unit. These are the things we’d talk through with you.
| Factor | Leans towards repair | Leans towards replacement |
|---|---|---|
| Age | Under roughly ten years and well looked after | Well into its second decade with a patchy history |
| Refrigerant | R32 or R410A | R22, which can no longer be used to recharge systems |
| Parts | Parts readily available | Boards, motors or compressors discontinued |
| Fault | Drain, fan, sensor, capacitor or joint leak | Compressor failure or a heavily corroded coil |
| Efficiency | Still performing close to its rating | Much less efficient than a modern equivalent |
| Suitability | Still the right size and type for the room | Room use has changed or it never coped well |
Can an R22 system still be repaired?
Only for faults that do not involve the refrigerant. R22 was phased out because of its effect on the ozone layer, and it can no longer be used to top up or recharge systems in the UK. An R22 unit that works can carry on, but any fault involving refrigerant loss usually means replacement. If you have an older unit, the refrigerant type is shown on the rating label.
An illustrative efficiency comparison
Suppose a room needs about 1,200 kWh of cooling and heating across a year. An old unit with an effective efficiency of 2.5 would use about 480 kWh of electricity, while a modern unit at 5 would use about 240 kWh. As an illustration only, at 25p per kWh that is roughly £120 versus £60 a year; use your own tariff and usage, as real figures vary.
Looking at the whole picture
Running cost savings alone rarely justify replacing a working system, but they can tip the balance when you are facing a large repair bill on an old unit. If replacement makes sense, our air conditioning installation page explains sizing, positioning and what a new system involves.
What affects the cost of a repair, and keeping faults from returning
What a repair costs depends on what’s wrong and what it takes to put right. We’ll explain what we’ve found and agree the work before we start. The main factors:
- Time needed to diagnose intermittent or electronic faults
- The parts required and whether they need ordering
- Whether refrigerant must be recovered, the circuit repaired, pressure tested and recharged
- Access to the units, such as high-level outdoor units, flat roofs or ceiling voids
- The type and size of system, from a single wall unit to a multi-room or commercial system
- Working outside normal hours for businesses that cannot have work during trading
Preventing repeat breakdowns
Many call-outs, especially leaks, smells and poor cooling, trace back to dirty filters, coils and drains. Regular air conditioning servicing catches these early, and businesses relying on several units often prefer a scheduled maintenance plan. For homes, our domestic air conditioning page covers the systems we look after.
We carry out repairs across the area, including Acomb, Clifton and Tadcaster. Call 0191 743 9144 or send us the details of the fault and we’ll arrange a visit.