Why does my aircon keep shutting off by itself?

One common cause is the float switch tripping because the drain is blocked and the pan is full. The unit shuts itself down to prevent overflow. A drain flush usually resolves this. See also the aircon-turns-off-by-itself article for other causes.

Can I clear the drain myself?

You can try blowing through the drain line from the indoor unit end with a wet-dry vacuum or by mouth. This sometimes clears light blockages. For heavy or biological blockages, a technician with a drain flush kit is more reliable.

Why does the drain keep blocking?

Algae and mould grow in the drain line when servicing intervals are too long. Regular servicing — which includes a drain flush — prevents this. If the drain blocks repeatedly between services, the service interval may need to be shortened.

Is a dripping aircon urgent?

It depends on where the water is going. Water dripping onto electrical fittings, ceiling panels, or timber flooring needs immediate attention. Water into a tray or bucket can wait for a scheduled visit as long as the unit is turned off.

Aircon drain pan and float switch

This is the overview page for drain-pan and float-switch faults. These two parts sit in the same drainage path, but the root cause is often a blocked drain pipe or ice-related overflow.

Parts summary

PartDrain Pan and Float Switch

LocationInside the indoor unit under the coil

FunctionPan collects water; switch prevents overflow

ImportanceStops water damage to ceilings and walls

Warning Signs

Water dripping from indoor unit or ceiling below
Unit shuts off suddenly and will not restart
Musty mold smell from the unit

What it is and where it sits

The drain pan sits under the cold coil inside your indoor unit. Water drips into it as the coil cools air.

The float switch is a safety sensor inside the pan. It detects when water rises too high and shuts the unit down.

Together they form the drainage safety system. The pan collects water. The switch prevents overflow.

Failure modes and warning signs

Drain pipes get blocked with algae and dirt. Water backs up and overflows the pan.

You see water dripping from the indoor unit or stains on the ceiling below it.

Sometimes the unit shuts itself off. The float switch detected high water and cut power to protect the room.

Water dripping from indoor unit or ceiling below
Unit shuts off suddenly and will not restart
Musty mold smell from the unit

How we verify the problem

Technicians flush the drain line first. A blocked drain causes most water leaks.

They check the pan for cracks or poor seating under the coil.

They test the float switch by checking if it trips when water level is high.

How we verify the problem summary table
Test Finding	What It Means	Next Step
Drain line is blocked	Blockage is causing backup	Flush and clear the drain
Float switch will not trip properly	Switch is broken	Replace the switch
Drain pan is cracked	Pan is damaged	Replace the pan
Coil is icing over	Refrigerant or airflow problem	Check coil condition

Should you fix it now?

Most water leaks are solved by flushing the drain. Replace the switch or pan only if those are broken.

You can wait if the drip is just occasional and water is not going anywhere critical.

Do not wait if water is damaging the ceiling, walls, or electrical equipment. Act immediately.

What to expect

Drain flushing is routine maintenance and very affordable.

Float switch replacement is quick and inexpensive if the drain is fine.

Finding and fixing the real cause saves time and prevents water damage.

Common questions

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Symptoms

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Cases

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Knowledge

Aircon gurgling noise from indoor unit