Why Does My AC Keep Turning Off by Itself?

The free checks: timer, sleep mode and the set temperature

Do these before anything else. Between them they explain a lot of “my AC keeps switching off” calls, and none of them costs a paisa.

• 1. Cancel any timer. Look at the remote and at the indoor display for a timer or clock symbol. Timers get set by accident with one stray button press, and a unit that switches itself off at the same time every night is almost always on one. Cancel it and watch for a night.
• 2. Turn off Sleep or Economy mode. Sleep mode deliberately drifts the temperature upward over a few hours and on many units shuts the machine down after a set period. It is designed to do exactly what you are complaining about.
• 3. Check the set temperature. If it is set high and the room is already cooler than that, the compressor will stop within minutes and stay stopped. The indoor fan usually keeps running, which is why people say it turned off when only the compressor did.
• 4. Note the timing precisely. Use your phone. Thirty seconds, five minutes, twenty minutes, or only in the afternoon. Write it down. This one detail does most of the diagnosis.
• 5. Note whether the fan keeps running. Indoor fan still blowing with the outdoor unit stopped is a different fault from the whole machine going dead. If everything including the display goes dark, read our page on an AC that will not turn on.
• 6. Clean the filters. Free, five minutes, and genuinely relevant — a choked filter is a real cause of protection cut-outs, covered below.
• 7. Record any blink pattern or error code shown when it cuts out, before you switch it off. See our guide on a blinking AC light.

When switching off is normal and not a fault

Two of these get reported as faults every day, and neither is one.

• It reached the temperature you set. This is how a non-inverter AC is supposed to work. The compressor runs until the room hits the setpoint, stops, and starts again when the room warms up. If your AC is set to a comfortable temperature in a well-shaded room at night, cycling on and off every so often is correct behaviour and a sign that the machine is healthy. The clue is that the room is genuinely cool when it stops. An AC that stops while the room is still hot is a different story.
• The restart delay. Almost every split AC waits roughly three minutes before restarting the compressor after it stops, to let pressures equalise. Start it too soon after a power cut, or switch it off and straight back on, and you get a unit that blows room air and appears dead for those three minutes. In a Delhi summer of short cuts and restorations this happens constantly, and it makes a perfectly healthy AC look broken. Give it five minutes before concluding anything.
• A very short cycle on an inverter unit is not normal. Inverter ACs are designed to run continuously at a varying speed rather than stopping and starting. If an inverter unit is cycling off every few minutes, that is a real symptom and worth investigating.

If the room is cool when it stops and comfortable when it restarts, you probably have nothing wrong. If it stops while the room is still hot, work through the sections below.

Voltage protection: the Delhi summer cause

If your AC cuts out mainly between roughly two and six on hot afternoons and behaves perfectly at midnight, suspect the supply before you suspect the machine.

When the whole colony’s air conditioners are running on the same transformer, the voltage at your socket can sag well below normal. Modern ACs and inverter units watch for this and refuse to run outside a safe window, because a compressor asked to start on low voltage draws more current, not less, and that is what burns motors out. So the board stops the unit, often flashes a code, and waits. A brownout, a dip during a generator changeover, or a supply restored after a long cut can all trigger the same protection.

• How to confirm it. The pattern is the confirmation: peak-hour cut-outs, quiet nights. If other appliances in the house also behave oddly at the same hours — lights dimming, a fridge clicking, a fan slowing — that is the supply, not the AC.
• Check the stabiliser. If the AC runs through one, listen to it. A stabiliser clicking repeatedly, buzzing, running hot or cutting out is at the end of its life and will cause exactly this. Borrowing a known-good one is a quick test. Our voltage fluctuation and stabiliser tips cover choosing and placing one.
• Is it DIY? Observing and recording, yes. Anything involving the distribution board or the supply side is an electrician’s job.

Overheating, blocked airflow and a failing capacitor

The other big family of cut-outs is thermal. Something is getting too hot or drawing too much current, and the protection stops it. These usually follow a consistent timing, which is why noting the minutes matters.

• A blocked or boxed-in outdoor unit — stops after fifteen to thirty minutes. The outdoor unit has to dump your room’s heat into the outside air. If it is crammed into a covered balcony, a light shaft, a grille cage or a duct with no free air around it, it re-breathes its own hot exhaust, the pressure climbs, and the protection cuts the compressor out. It cools fine for twenty minutes and then gives up, every time. This is one of the most common causes in Delhi flats and it is a placement problem, not a broken part. Our guide on outdoor unit placement covers the clearances a unit actually needs.
• A dust-caked outdoor coil — same timing, same reason. Even a well-placed unit chokes if the fins are matted with Delhi dust. Same symptom, and the fix is a proper coil wash rather than moving anything.
• A dirty filter or a frozen indoor coil — often stops after a longer run. A choked filter starves the indoor coil of air, the coil gets too cold, ice forms, and the unit either cuts out on a sensor or simply stops cooling and then stops. Look for frost on the copper pipe or the indoor coil. Our page on an AC icing up goes through this.
• A failing capacitor — stops within seconds or a minute or two. The capacitor gives the compressor and outdoor fan the kick to start. When it weakens, the compressor tries, strains, overheats and drops out on thermal overload almost immediately, then tries again a few minutes later. You often hear a hum or a grunt from the outdoor unit at each attempt. It is a small, common, inexpensive part and it is the first thing to ask about for very short cycles.
• A seized or failing outdoor fan motor. If the outdoor fan is not turning, the compressor runs without any cooling of the coil at all and cuts out quickly on temperature. Check whether the fan is spinning while the unit runs.
• A dirty or failing sensor. A misreading temperature sensor can convince the board the room or the coil has reached a limit when it has not. Usually accompanied by an error code.

None of these are DIY beyond washing the filters and clearing obstructions away from the outdoor unit. Do not open covers on the outdoor unit, and never touch a capacitor — it holds a charge after the power is off.

When to call someone, and what to tell them

Call once the timer and sleep mode are cancelled, the filters are clean, the outdoor unit is clear, and it still cuts out while the room is hot.

• Lead with the timing. “It runs for exactly twenty minutes then the outdoor unit stops” or “it cuts out within a minute with a grunt from outside” are two different jobs and two different parts to carry.
• Say what stops. Whole unit dark, or indoor fan still running while the outdoor unit stops. This matters.
• Say when it happens. Only on hot afternoons, at all hours, or only after a power cut.
• Read out any error code or blink pattern exactly as you counted it.
• Say where the outdoor unit is installed — open wall, covered balcony, light shaft, boxed in behind a grille. Half the answer is sometimes in that sentence.
• Ask for the supply voltage and running current to be measured. Both are real numbers a competent technician can give you.

Hold firm on a few things. Ask for the capacitor to be tested and ruled out before anyone talks about a compressor. Do not accept a gas refill for a cut-out complaint unless a leak has actually been found, since refrigerant level is not what triggers most protection cut-outs. Ask what was measured, not just what was concluded. Ask for the old part back. And get a second opinion before agreeing to a compressor or a control board.

Two cases belong elsewhere. If the breaker is down every time it stops, go to our guide on an AC that trips the MCB or on an MCB that keeps tripping. If the unit never restarts at all, read an AC that will not turn on. And if the outdoor unit stays silent while the indoor unit keeps blowing, see an outdoor unit that is not running. Regular servicing prevents most thermal cut-outs outright — our AC service guide and summer AC care tips cover what that involves.