How can I check my aircon gas at home?
To check aircon gas at home, run the aircon on 20°C for 10 to 15 minutes, then look for frost on the copper pipes at the outdoor unit and feel the indoor cooling coil. Cold and wet all over usually means the gas is enough. Frost on the pipes or coil usually means low gas and a leak somewhere. Key takeaways
- Settings matter: 20°C, fan speed 2 or 3 and every unit on the same system switched on, for 10 to 15 minutes.
- Frost is the clearest sign: ice on the pipes or coil usually means the gas is too low.
- A cold, wet coil is good: water on your hand shows the coil is pulling moisture from the air.
- Touch can't measure the gas: only a technician's tools show whether there is too little or too much. In the video above, Uncle Eric walks through both checks step by step, and ends with a bonus test you can use to see whether your last aircon service was done properly.
Step-by-step: the aircon gas self-check
- Set the aircon up. Turn it on at 20°C with fan speed 2 or 3, not the maximum, and leave it running for at least 10 to 15 minutes. On a System 2, 3 or 4 multi-split, turn on every indoor unit connected to the same outdoor unit. If you have separate systems, test each one on its own.
- Look at the outdoor unit, if you can see it safely. This works if you have an aircon ledge and can see the outdoor unit directly from a window. If you see frost or ice on a copper pipe, the gas is usually too low: you can stop here and book a check. If your outdoor unit is on a wall bracket or too far to see, go to step 3. Don't lean out or climb onto the ledge.
- Reach the indoor unit safely. Use a tall, sturdy chair or a small ladder, ideally with someone holding it. Switch the aircon off, lift the front cover and slide out the air filters, then switch it back on and give the coil a few minutes to get cold again.
- Touch the cooling coil. It is the block of thin metal fins behind the filters. With your fingers and palm, touch the top, then the bottom, then the left, then the right. Press gently: the fins are thin and the edges can be sharp.
- Read the result using the table below.
What the coil check tells you
What you feel | What it usually means | Next step |
|---|---|---|
Cold all over, and your hand comes away wet | Gas is enough | Do the airflow test below |
Cold in some areas, warm or dry in others | Gas may be low, or airflow is poor | Book a check |
Frost or ice on part of the coil | Gas is not enough, likely a leak | Switch off and book a check |
| Not cold anywhere | The compressor may not be running | Book a technician | Water on your hand is a good sign. It means the coil is cold enough to pull moisture out of Singapore's humid air, which is exactly what it should do. One caution: frost can also appear when a very dirty coil or blower fan chokes the airflow. Either way, frost is a sign to get the unit checked, not to keep running it. If your result is in rows 2 to 4, our gas top-up service starts by measuring the system, and recommends a leak check before adding gas if the charge is low. If the check points to low gas, our guide to aircon gas leak signs explains how the leak is found and why a top-up alone won't last.
Bonus: was your last service done properly?
Put the filters back, close the cover and move your hand slowly across the air vent from left to right. If the blower fan and coil are clean, the air comes out evenly across the whole vent. Signs of a dirty fan or coil, or a service that took short cuts:
- one side blows much stronger than the other
- the centre is weak or has no air at all
- the coil is cold but almost no air comes out That last one means you are paying for electricity to cool a coil whose cold air cannot reach the room. A proper premium servicing with PowerJet takes the blower fan out and cleans it along with the coil. If you recently had a service and still see these signs, read why an aircon is still not cold after servicing. Uncle Eric also posted a follow-up to this guide (watch: DIY gas check follow-up).
What can't you check yourself?
These checks tell you whether something is likely wrong. They can't tell you:
- how the gas is actually performing. A technician connects measuring tools at the outdoor unit and checks it while the aircon runs.
- whether the amount of gas is exactly right. We confirm it with digital tools, never by feel.
- whether the system has too much gas, which hurts efficiency and strains the compressor as much as low gas.
- where the leak is, which needs a leak detector, a bubble test or a leak test on the pipes.
- electrical or compressor faults inside the outdoor unit. Never open the outdoor unit, touch the wiring, or try to add gas yourself. If gas turns out not to be the issue, our guide to why an aircon is not cold covers the other common causes.
When to call a technician
Book a check if:
- you see frost or ice on the pipes or the coil
- the coil is cold in some places and warm in others
- the coil is not cold anywhere after 15 minutes
- the airflow is weak or uneven even after you clean the filters
- cooling keeps fading after a previous gas top-up Every iAircon service includes a 90-day warranty. You can book online in under a minute, or chat with Luna, our AI assistant, on WhatsApp 24/7.
Frequently asked questions
Can I buy a can of refrigerant and top up my aircon myself?
No. Gas has to go in at the outdoor unit with proper tools and the correct refrigerant, and the system has to be leak-free and cleared of air and moisture first. R32, used in most newer aircons, is also mildly flammable, so charging it is a job for a trained technician.
Does water dripping from the coil during the check mean my aircon is leaking?
No. Water on a cold coil is normal condensation, which the drain tray carries away. It is actually a good sign in this check, because it shows the coil is cold enough to pull moisture out of the air.
My coil is cold everywhere but the room is still warm. What now?
Then gas is probably not the problem. Do the airflow test across the vent: weak or uneven air points to a dirty blower fan or coil. If the airflow is strong too, the unit may be undersized for the room or have another fault that a technician should check.
How often should I do this check?
Only when you notice cooling getting weaker. A healthy sealed system does not lose gas, so there is no need to check routinely. If the check suggests low gas, book a technician rather than waiting, since running low strains the compressor.
Can I tell by touch if there is too much gas?
No. Too much gas strains the compressor as much as too little, but it cannot be felt on the pipes, which is why a top-up must be measured by a technician.
Eric Lim, aka Uncle EricFounder of iAircon.Repair, now in its 10th year servicing aircons in Singapore. Every job is filmed, so you can watch the work on YouTube.
