Air conditioning not cooling: 7 causes to check yourself

Air conditioner, removable filter and remote in a bright room

Air conditioning breaks down in the hottest week of the year — not out of spite, but because that is exactly when it runs twelve hours a day. Some of the causes can be found and put right in ten minutes with no engineer. The rest need a tradesperson, but the description you give them decides whether they come once or twice.

1. Dirty filters

The most common reason for weak airflow and a room that will not cool down. The filters come out of the indoor unit, get washed in lukewarm water, dried completely and put back. Do it every few weeks in the busy season — on the coast the dust and the salt build up faster.

2. The outdoor unit is boxed in or in direct sun

The outdoor unit throws the heat outside. If it is bricked into a recess with no ventilation, covered with plastic sheeting or overgrown, the air conditioning cannot keep up. Clear at least half a metre around it and check that the fins are clean.

3. Low refrigerant

If the unit runs but cools poorly and the pipes ice up, the refrigerant level has most likely dropped. This is not a consumable — refrigerant is not "used up". If it is low, there is a leak, and the leak has to be found; otherwise a top-up will last one season.

4. A blocked drain

If water drips from the indoor unit into the room, the drain pipe is usually blocked. The water that should be going outside comes back in instead. Switch the unit off so that it does not soak the wall, and call an engineer — clearing it is a quick job.

5. A smell when it starts up

It smells of damp or of mould, because a biological film has grown inside the unit. Disinfecting the evaporator and the drain sorts it out. If the smell is of burning, switch it off and do not start it again.

6. It will not start at all

Check in order: is there power at the socket, has the circuit breaker in the consumer unit tripped, are the batteries in the remote flat, is it set to fan rather than cooling. Surprisingly often it is one of those four things.

7. The compressor or the board

If the outdoor unit will not start, hums and stops, or the air conditioning restarts itself, the problem is a serious one. This is where self-help ends: it needs a proper diagnosis, and the cost of the repair gets weighed against the cost of a new unit.

Why they fail more often by the sea

Salt air is the outdoor unit's main enemy. It eats away at the fins, the pipe connections and the casing — a process that runs far faster in Sarafovo, Kraymorie, Briz or Asparuhovo than it does twenty kilometres inland. That is why a service once a year here is not a recommendation but a condition of the unit lasting its natural life.

The second thing is the seasons: flats stand shut over the winter, damp gets into the unit, and in June the air conditioning is switched straight to maximum after seven months of standing still.

When to book a service

April and May. In July and August engineers on the coast are busy with breakdowns and servicing gets pushed back. A pre-season check covers cleaning the filters and the units, checking the drain, measuring the pressure and inspecting the outdoor unit for corrosion — and it usually saves an emergency call-out at the peak.

What to write in the request

Make and model, year, exactly what the unit is doing (blowing warm, dripping, not starting, noisy), since when, which floor the outdoor unit is on and whether there is access to it. If a rope access technician is needed, it is better to establish that beforehand than on arrival.

How to book an engineer

Describe the problem — offers usually arrive within 5–15 minutes:

If the breaker trips when the air conditioning comes on, the problem may be in the wiring — in which case you need an electrician.