Check the remote is sending
Replace both batteries with fresh ones of the same type, not one new and one old. Point the remote straight at the indoor unit from a few metres away. Most remotes use infrared, which you can't see but most phone cameras can: look at the tip of the remote through your phone camera and press a button. A flicker of light means it's sending.
Check the display too. A key or lock symbol usually means a child lock is on, and the manual shows how to release it. Some remotes have a reset button inside the battery cover. If the remote's screen shows nothing at all with fresh batteries, the remote has probably failed, and a replacement made for your model is usually the simplest fix.
Check the unit has power
Look for any light on the indoor unit's display. If it's dark, check the switchboard for a tripped circuit breaker or safety switch, and check the isolator beside the outdoor unit hasn't been switched off by someone working nearby. Many indoor units also have a small manual operation button under the front panel. If the unit starts from that button, the problem is the remote or the receiver, not the power.
When it's the receiver
The receiver is a small sensor behind the display window on the indoor unit. If the remote is clearly sending, the unit has power and it starts from the manual button but ignores the remote, the receiver or control board is the likely fault. Strong sunlight on the receiver can interfere with the signal, so try again with the blinds drawn. If a Wi-Fi app still controls the unit, that also points to the receiver.
What you can safely do now
- Fit fresh batteries and check the remote's display for a lock symbol.
- Use a phone camera to check the remote's tip lights up when you press a button.
- Check the switchboard for a tripped breaker or safety switch, and reset it once.
- Check the isolator next to the outdoor unit is on, but only if its cover is intact and dry.
- Try the manual operation button on the indoor unit if your manual shows one.
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Related questions
- Why does my air conditioner turn off by itself?Most often a setting is doing it: an off timer, sleep mode, an eco or quiet mode, or an app schedule someone else set up.
- What is the switch next to my outdoor unit for?It's an isolating switch that cuts all power to the air conditioner, so a technician can work on the system safely without relying on the switchboard.
- My air conditioner won't restart after a power outage. What now?Give it a few minutes first.
- Why does my air conditioner keep switching on and off?Frequent stopping and starting, called short cycling, usually means the unit reaches its set temperature too quickly or keeps tripping its own protection.
Sources for this answer
1 source, with the date each was checked
- 1.Energy Safe Victoria: Locate your electricity box outside your home and check whether the safety switch has tripped. If it has tripped, reset the switch. If the switch won’t reset, call a licensed electrician. Accessed 30 September 2026.
General information for homes in Victoria. Every installation is different, so treat this as a starting point. Where this answer refers to Victorian safety or rental rules, the sources above have the current requirements.