6 Reasons why Aircon cannot turn on and how to fix it?

General Guide to Aircon Cannot Turn On

It is really frustrating to go home in a hot day just to find out if your aircon cannot turn on. Worst still is if your irritating sister’s is working and she is standing there laughing at you. Schadenfreude. So as you are standing there wondering why Aircon turns on. Fret not, here in this Article we will guide you through the reasons why the Aircon is not able to switch on. And we will go through some solutions to fix it.

aircon cannot turn on

If you are too lazy to read this article,



Which brand of Aircon cannot turn on?

There are many different aircon brands like Mitsubishi, Panasonic, Midea and etc. Does the brand of your Aircon matters in why your Aircon can’t turn on? To a certain extent, yes. As there are some models of certain brands that have specific parts that tend to spoil easily. That Aircon parts may cause the Aircon to be unable to turn on. Often, people experience Mitsubishi Aircon cannot turn on for various reasons, just like the other brands.

6 Reasons why Aircon cannot turn on

Defective indoor Aircon PCB


If it is a multi split Aircon unit. Which means that one condenser unit is connected to many indoor units. And only one aircon unit cannot turn on, it is most likely the indoor unit PCB that is malfunctioning. However if you are able to turn on this manually, it could be other reasons causing it. Read the next paragraph to find out,


Indoor Sensor Malfunctioning


Assuming it’s a multi split Aircon and it can be turned on manually but not with an Aircon remote control. Then it is most likely the indoor Aircon sensor receiver that is faulty. Hence the sensor is unable to receive the signal from the remote control and it is unable to turn on. Thankfully this is a relatively inexpensive parts to fix.


Broken Wire


If it cannot be turned on manually or with the remote control. Then it could be the wiring connecting from the fancoil unit to the condenser unit that is faulty. This wiring may be hard to change, depending on the set up of your house. If this is a condo or landed property the wiring may run through false ceilings. You will have to cut through false ceilings in order to change them. Which is costly and generally requires more time to clean up.

broken wire

Outdoor PCB Board


Aside from the above parts, it could also be the outdoor unit that is faulty. However this is extremely rare. Outdoor PCB is a motherboard that contains many components. In this case it is just the portion that connects the wire to the indoor unit that is malfunctioning. This is assuming if only 1 unit of the multi split unit is malfunctioning. For example, if all of your Mitsubishi Aircon cannot turn on, then there is a high change it is the outdoor PCB that is spoiled.


Broken Isolator


A broken isolator could also cause improper electrical connectivity to the outdoor condenser unit. Hence power cannot be relay to the indoor unit. Hence all of the Aircon units stop working. However if only one aircon unit not working in a multi split aircon setting, then it is likely not due to isolator.


MCB to Aircon Isolator Wire


Generally this is the hardest problem to fix. If the wiring connecting from the Distribution Box / DB box to the Aircon isolator is malfunctioning. You will have to replace the entire wiring all the way from the Miniature Circuit Breaker (MCB) to Aircon isolator. How troublesome this is depends on how long the wiring is. It also depends if the wiring is being concealed. For landed property, the wiring may be concealed deep behind the wall, which may require hacking to access it.


Click to find out more

Aircon Temperature Issues
Aircon Temperature Issues?
Aircon Water Leak
Aircon Water Leak?
Automatically Turning OnOff
Aircon Automatically Turning On/Off?
Aircon Error Code Problem
Aircon Error Code Problem?

How to fix aircon cannot turn on?

Change indoor PCB or sensor receiver


If one unit Aircon cannot turn on in a multi split Aircon system, there is a 90% chance it is either of this Aircon spare parts that is malfunctioning. Hence we generally just need to replace the parts to make it work. The cost of replacing this parts will be $120 onwards. That depends on the rarity of the model. Furthermore it also depends if you require a brand new or refurbished parts.

Changing aircon isolator


If your Aircon isolator malfunctions, it is a relatively simple component to change. It should easily cost below $150 to replace the Aircon isolator. However it is the work taken to find out the problem that is more costly. Because the Aircon technicians will have to troubleshoot through a lot of parts to figure this out.

Aircon cannot turn on due to outdoor Aircon PCB board


This is one of the more expensive problems to replace. As the outdoor Aircon PCB board is one of the most expensive components in an Aircon system. The most expensive ones being Aircon compressor. However, this is usually rare for. Nevertheless, there is usually a few Aircon PCB inside the circuit box of the condenser unit. You will likely only need to replace the control board. Unless it is the power board causing the failure. I am unable to give an estimation to how much this will cause as it depends on the model.

Change of wiring between fancoil to condenser unit


Again, the difficult of this very much depends on the set up of your house. For HDB, we are usually able to give an estimated price. It will likely cause below $280. However for condo or landed properties, we will need a site visit to estimate the cost of the the works. Fingers crossed that it is not this issue that causes Aircon cannot turn on.


Click to find out

Conclusion :

If your are unable to turn on your aircon, fret not as it is usually a problem that is traceable. You may be able to figure out the root cause via some of the methods shown above. However if you are still not sure why your , feel free to WhatsApp us. We will be able to give you an estimated price of repair and send someone down to assist you if possible.

Tagged in
Leave a reply