It cuts out every afternoon and comes back.

Air conditioners have a high pressure switch on the discharge side. When head pressure exceeds a set limit, it opens and stops the compressor before something gives. It is a safety device doing its job.

The symptom from inside the house is a system that cools, quits, waits, and tries again, usually only when it is hot out.

The afternoon pattern is the clue

Head pressure rises with outdoor temperature, because the condenser coil has to reject heat into hotter air. A system with a marginal condenser runs fine at 85 and hits the limit at 112.

So note the times. A system that behaves all morning and trips at three every afternoon is telling you the condenser side is marginal, before anybody measures anything.

The cheap causes, in order

A fouled condenser coil. The overwhelming favourite in this city. Monsoon dust packs the fin pack, the coil cannot reject heat, and pressure climbs. A chemical clean is a flat price and it fixes a surprising number of these.

The condenser fan not running, or running slowly. No airflow means no heat rejection. A fan that will not start is usually a capacitor, which is cheaper still.

Blocked airflow around the unit. Oleander grown into it, a fence built too close, storage leaned against it, or anything over the top. The unit throws heat upward and pulls air in from the sides, and it will happily recirculate its own exhaust.

A dirty or recirculating installation. Two units close together on a side yard, or a unit in a tight alcove, can feed each other hot air.

The expensive causes

Overcharge. Too much refrigerant raises head pressure directly. This is a service-induced fault, and it is one of the arguments for getting readings rather than top-ups.

Non-condensables in the system, meaning air or moisture that got in during a previous repair and never got vacuumed out.

A restriction in the liquid line, such as a blocked filter drier.

A failing compressor on its way out.

What a diagnosis takes

Head and suction pressures together, outdoor temperature at the time, amp draws, and the condenser condition. Those numbers separate a dirty coil from an overcharge from a compressor, and they are the difference between a flat priced clean and a much larger conversation.

Take the numbers when it is actually tripping, which means an afternoon visit rather than a morning one. Worth saying when you book.

While you wait

Clear two feet around the outdoor unit and rinse the fins gently with a hose, power off at the disconnect first. That alone sometimes stops the tripping, and it costs nothing.

Do not keep forcing restarts. Each one runs the compressor up against the limit again.