Why your AC runs but stops cooling

The gas has leaked out

This is the first thing to suspect and the easiest to confirm. The unit starts, the fan runs, the air moving out of it is barely cooler than the room. Sometimes there is ice on the copper line near the outdoor unit.

Refrigerant is a sealed system. It does not get used up, so if it is low, it left through a leak. Topping up the gas without finding that leak buys a few weeks and then the same call comes again. Ask whoever services the unit to find the leak, not just charge it.

The gas valve is not holding

A unit can hold its charge and still fail to cool if the valve is not doing its job. The symptom looks similar from the room, which is why guessing over the phone is unreliable and why we look at the unit before quoting.

The PC board has failed

When the board goes, the unit usually behaves strangely rather than dying outright. It starts and stops on its own, ignores the remote, runs the fan without the compressor, or throws an error code and resets itself.

This is the expensive end of the list, which is exactly why it should be diagnosed rather than assumed. A board replacement and a gas charge are not remotely the same job or the same bill.

It has simply gone too long without a service

A filter and coil packed with dust chokes the airflow. The unit works harder, cools less, and draws more power doing it. In Lahore this builds up fast, and a unit left through the dust of a construction season is often the one that fails first in summer.

The tell is that cooling has faded gradually over weeks rather than stopped suddenly. That pattern points to cleaning, not to a part.

What to check before you call anyone

Two minutes of checking saves a wasted visit. Confirm the unit is actually getting power and that the breaker has not tripped. Set the thermostat well below room temperature so you know the unit is being asked to cool. Look at the filter, since a visibly grey filter tells you most of the story. Note whether the outdoor unit is running at all, because a silent outdoor unit and a running indoor one is a different fault from both being on.

Tell the technician what you saw. It shortens the diagnosis, and for a building with several units it helps decide which one gets attention first.

When one unit is a sign about the rest

In an office, hospital or hotel, units are usually the same age and have had the same maintenance history. The one that failed is often the first of several. If a building is on its second or third breakdown of the season, the useful question stops being about that unit and becomes about the maintenance schedule for all of them.