Many split air conditioning units fitted in UK homes can heat as well as cool. They work as air-to-air heat pumps, and the remote has a heat setting for the colder months. If yours has spent the summer on cooling, the first few weeks of heating are often when a problem shows up.
Some of what happens in cold weather is normal, and some of it means the unit needs an engineer. Here is how to tell the difference.
Start With The Simple Checks
Before you book anyone, rule out the easy causes:
- Check the remote is set to heat, not cool, dry or fan, and that the target temperature is above the room temperature.
- Clean or check the filters. Clogged filters restrict airflow, so the unit has to work harder to warm the room.
- Look at the outdoor unit and clear away anything blocking it, such as fallen leaves or garden furniture moved for the winter.
What Is Normal In Cold Weather
In heating mode, the coil in the outdoor unit gets very cold. Moisture in the air condenses and freezes on it, so the unit regularly stops to melt the frost. This is called the defrost cycle.
Fujitsu, for example, explains that during defrost the indoor fan slows or stops so cold air does not blow into the room, and the operation light may stay on or blink slowly. It says the cycle usually lasts between five and fifteen minutes, after which heating carries on. If your unit goes quiet for a few minutes on a cold morning and then starts heating again, that is likely all it is.
Signs It Needs A Repair
These are worth getting looked at by an engineer:
- Heating does not come back after defrost. Fujitsu notes that a defrost that lasts unusually long, or does not return to normal operation, may need further inspection.
- Defrosting all the time. Persistent or very frequent defrost cycles can point to a performance problem.
- Ice that will not clear. Units freezing up is a common reason for a repair call-out.
- Water dripping from the indoor unit. A blocked condensate drain is a common cause.
- Weak airflow or lukewarm air. If the filters are clean and the air still barely moves, the cause may be a dirty coil or a fan motor fault.
- Unusual noises or smells. An unusual noise or a stale smell from the unit is a sign that something is not right.
- Error codes or flashing lights. Faults in the unit’s circuit board often show as a code on the display or a pattern of flashing lights. Note it down before you call, as it helps the engineer diagnose the problem.
Leave The Refrigerant To A Certified Engineer
Refrigerant leaks and a low refrigerant charge are among the most common air conditioning faults, and they are not a DIY job. Air conditioning contains fluorinated gases, so the company doing the work needs an F-gas certificate from an approved body such as Refcom.
Government guidance on F-gas leak checks also says that when a leak is found, it must be repaired as soon as possible and checked again within a month to make sure the repair worked.
Repair Or Replace?
Whether a unit is worth repairing depends on how serious the fault is, whether parts are still available, the type of refrigerant it uses, its age and how efficient it is. A good engineer will give you a written diagnosis and a quote before doing any chargeable work, and tell you plainly if replacement would cost less in the long run.
If you are in the capital, a service that offers air conditioning repair in London, such as JP Air Conditioning, can diagnose the fault and advise whether a repair makes sense. When you compare engineers, ask about F-gas certification, manufacturer approval for your brand and public liability insurance, and read independent reviews.
Keep It Heating Well
A unit that heats and cools works hard all year round, so keep the filters clean and book a service at least once a year.
