The air conditioning runs but does not cool. It switches on, the fan is audible, air comes out of the vent, and the room stays exactly as warm as it was. It is one of the most common calls we get in August, and the good news is that the cause is often something you can sort out without calling anybody.
Let us work through it in order, cheapest and simplest first. And with a distinction almost nobody makes for you on the phone: which part of this is an electrician's job and which part needs a refrigeration engineer, because they are not the same trade or the same certification.
First: what you can check yourself in ten minutes
1. The filters
Cause number one by a distance. The filters in the indoor unit clog with dust and the system stops moving enough air. On the coast, between ordinary dust and calima (Saharan dust haze), they clog far faster than people expect. Open the unit, slide them out, rinse them, dry them completely, put them back. No tools needed.
2. The outdoor unit
The unit outside is what dumps your home's heat. If it is jammed against a wall, covered with a tarpaulin, full of leaves or boxed in behind furniture, it cannot do that. It needs free air all around it. A surprising number of "broken" systems start cooling again the moment the outdoor unit is cleared.
3. Mode and temperature
It sounds obvious and it is not: the remote left on fan instead of cool, a set temperature above the room temperature, or a timer still running. Worth the thirty seconds before anything else.
4. Doors, windows and blinds
A living room with the blind up and direct afternoon sun can take on more heat than the unit can remove. That is not a fault, it is a heat load winning the argument.
If that was not it: the causes you cannot fix yourself
With the simple things ruled out, we are into engineer territory. This is where it helps to know who to call.
- Low refrigerant: the circuit is sealed, so if gas is low there is a leak. Recharging without finding it is money thrown away. Work for a qualified refrigeration engineer.
- Fan or compressor: if the outdoor unit will not start, makes an unusual noise or vibrates differently, there is a mechanical or internal electrical fault.
- Sensor or control board: the unit "believes" it has already reached temperature and stops working.
- Undersized unit: not a fault at all. If the equipment was too small for the room, it will never get there on the hottest days however new it is.
- Poor original installation: badly insulated pipework or an incorrect gas charge at commissioning drags performance down from day one.
When it IS electrical (and that part is ours)
Some symptoms point at the installation rather than the machine, and they are worth recognising because a few of them should not wait:
A breaker trips on start-up. The compressor draws a surge as it starts. If that trips the diferencial (RCD) or magnetotérmico (MCB), something in the board or the circuit needs checking. We cover it in why your air conditioning trips the electrics.
The plug or cable gets hot. An appliance of this size on a circuit that cannot carry it is a genuine risk. If there is a smell too, switch it off and leave it off: see what to do about a burning smell.
It shuts down and restarts by itself. That can be the unit's own thermal protection, but it can equally be an unstable supply or a loose connection in the board.
It was fitted without its own circuit. Air conditioning should have its own line from the cuadro eléctrico (consumer unit), with its own protection. Hanging it off a shared socket circuit is behind a good share of the problems we see.
Why it bites harder on the Costa del Sol
Two things work against you here. First, season length: a unit that runs three weeks a year inland runs for months on the coast, and skipped maintenance is paid for sooner. Second, airborne dust and salt near the sea clog filters and heat exchangers far faster.
On top of that, plenty of older properties in central Málaga have had units added over the years to an installation never designed for them. If yours is one of those, an installation check is worth it before another summer.
Maintenance that prevents the August phone call
Clean the filters during the season, not just at the start. Twice a summer minimum, more with pets or on a dusty street.
Keep the outdoor unit clear. Free space around it, no covers or stored clutter, and clear the leaves and dirt before the heat arrives.
Switch it on before you need it. Testing in May rather than on the first 38-degree day is the difference between sorting it calmly and waiting a week at peak season.
Frequently asked questions
Why is my air conditioning running but not cooling?
The most common causes, and the cheapest to fix, are clogged filters and an outdoor unit that is covered or obstructed: the unit runs but cannot shift the heat. After that come low refrigerant from a leak, a fan or compressor fault, and a unit that was undersized for the room in the first place. Always work through the simple things before calling anyone out.
How often should the filters be cleaned?
On the Costa del Sol, with dust and calima (Saharan dust haze), check them every few weeks through the season and clean them at least a couple of times each summer. It is a ten-minute job needing no tools, and it restores cooling capacity and lowers running costs.
If it is low on gas, can it just be topped up?
No. A refrigeration circuit is sealed, so if gas is low there is a leak, and recharging without finding it only buys a few months. Handling refrigerants is also regulated work and must be done by a qualified refrigeration engineer, which is a different trade and a different certification from an electrician.
Could it be an electrical fault rather than the unit?
Yes, and more often than people expect. If the unit starts and stops on its own, if a breaker trips when it starts up, or if the plug or cable gets hot, the problem is in the installation rather than the machine. That is electrician's work, and it is worth stopping use until it has been checked.
Can a small unit cool a large room?
No, and it is a very common source of complaints. If the unit is below what the room demands it will run constantly, cost a lot, and still fail to reach temperature on the hottest days. Orientation, insulation and the amount of glazing matter as much as the floor area.
Think the problem is the installation?
VLR Instalaciones has spent more than 20 years on electrical installations across Málaga and the province, as electricians authorised by the Junta de Andalucía. We check the electrical side of the system — circuit, protective devices, connections and whether the line is sized for the load — and tell you plainly whether you need an electrician or a refrigeration engineer. Get in touch for a no-obligation air conditioning check.