Split Systems: What Actually Goes Wrong

A split system that is not cooling well is usually not broken. It is dirty, low on refrigerant, or draining badly, and all three are maintenance rather than repair.

The filter is most of it

The indoor unit pulls air through a filter. That filter loads up with dust, and a loaded filter restricts airflow.

Restricted airflow means less air across the coil, which means less cooling, which means the unit runs longer to reach the temperature, which means it uses more power to do less. In bad cases the coil ices up, and a unit with ice on the coil stops cooling entirely.

Filters are designed to be cleaned by the occupant. In practice, on a rental property, they frequently are not, for years.

The coils behind the filter

Behind the filter is the coil itself, and over time it gets a coating that a filter clean does not touch.

That needs a proper service rather than a wipe. A coil that is coated will underperform even with a clean filter, and it is the reason a unit that had its filter cleaned still is not cooling properly.

The outdoor unit has the same problem in a different way. It needs airflow around it, and it is routinely boxed in by plants, stored items or a fence built after it was installed.

Water in the wrong place

The indoor unit produces condensate and drains it away through a small pipe. That pipe blocks with the same dust and biological growth that everything else collects.

When it blocks, the water goes somewhere else, which is usually down the wall inside. The first sign is often a stain rather than a puddle, and by then it has been happening for a while.

That is why a unit dripping inside is treated as a drainage problem, not a leak, and why it frequently turns into a two-trade job once the wall is involved.

Refrigerant does not get used up

A system that is low on refrigerant has a leak, because it is a sealed system. Topping it up without finding the leak means doing it again next season.

Any conversation that starts with a top-up should include finding out where it went.

What a service should cover

Filters cleaned, indoor coil cleaned properly, drain cleared and tested, outdoor unit cleared and cleaned, refrigerant pressures checked, electrical connections checked, and the unit run through a full cycle to confirm it performs.

That is a real service. Wiping a filter and calling it done is not.

When to book it

Before the season, not during it. A unit that has run all summer on a blocked filter has been working hard for months, and the service that would have prevented that is cheaper than the repair that follows.

On managed properties an annual service ahead of summer removes most callouts in the months when everyone is trying to book at once.