Why are all my aircons not cold at the same time?
When all aircons are not cold at the same time, the cause is usually something they share. On a System 2, 3 or 4, every room runs on one outdoor unit, one power supply and one gas circuit, so a tripped isolator, a stopped outdoor unit or low gas hits every room. Separate indoor faults rarely appear on one day. Key takeaways
- Look at what they share: one outdoor unit, one compressor, one power supply and one gas circuit.
- Power first: a tripped breaker or isolator is the quickest thing to rule out.
- Low gas affects every room: on a multi-split, all indoor units draw from the same refrigerant.
- Dirty units fade unevenly: dirt builds up room by room, so it rarely explains a same-day failure. In the video above, every aircon in the home had stopped cooling. The customer booked a gas check and our infrared leak check: we scanned the outdoor unit and all three indoor units and checked every flare joint. No leak showed up, so we topped up the R32 gas to the correct charge, and all three rooms cooled again.
How to narrow it down
Work through these in order:
- Check the power. Make sure the aircon's circuit breaker has not tripped and the isolator switch is on. If the breaker has tripped, reset it once; if it trips again, stop and call a technician. Never climb onto the aircon ledge to check anything.
- Look at the outdoor unit. With the aircon on cooling, the outdoor fan should spin and you should hear the compressor. If the indoor units blow but the outdoor unit is silent, the fault is likely there.
- Check for blinking lights. A blinking light on the indoor units is an error code. On a multi-split, the same code on every unit often points to the outdoor unit. Note the pattern before you call.
- Check the outdoor unit's airflow. A condenser coil caked in dust, or a unit boxed in by plants or storage, cannot get rid of heat. In afternoon sun, that can drop cooling in every room.
- Suspect the gas. If power, outdoor unit and airflow all look normal, low refrigerant is the likely cause. That needs a gas check and, if it keeps happening, a leak check. If step 5 is where you land, book a gas check. If a breaker keeps tripping or there is an error code, book troubleshooting instead. Every room hot right now? Message Luna on WhatsApp.
Shared cause or separate problems?
What you notice | Likely cause | Next step |
|---|---|---|
All rooms warm on the same day, outdoor unit silent | Power, outdoor PCB, fan motor or compressor fault | Troubleshooting visit |
All rooms weak, outdoor unit running, pipes frosting | Low gas | Gas check, then leak check if it recurs |
All rooms weak in the afternoon only | Outdoor unit in sun, dirty condenser coil or blocked airflow | Servicing, clear the space around it |
Same blinking code on every unit | Fault reported by the outdoor unit | Note the code, book troubleshooting |
| One room weak, others fine | That indoor unit: dirty coil, filter, blower fan or sensor | Servicing or chemical wash for that unit |
Why low gas hits every room
On a System 3, one outdoor unit pumps refrigerant to three indoor units through separate pairs of copper pipes. They all share the same charge. If some gas escapes anywhere, at a joint in the bedroom or a valve on the ledge, every room gets less cooling. That is why we scan all the indoor units and joints, not just the one the customer noticed first. The gas does not get used up. If it is low, it escaped. In this job no leak showed on the day, which happens with very slow leaks. If cooling fades again after a correct top-up, the next step is a repeat leak check, with a bubble test on every joint and along any piping we can reach; our post on aircon gas leak signs explains what to watch for. For the one-room version of this problem, read 6 causes of an aircon that is not cold.
What it costs
Job | Price | What drives it |
|---|---|---|
Gas check and top-up | S$165 | Paid at booking; R32, R410A or R22 |
Infrared leak check, 1 to 3 units | S$580 | Number of units and joints |
Infrared leak check, 4 to 5 units | S$880 | Number of units and joints |
| Inspection and troubleshooting | S$150 | Diagnosis visit; parts and repair extra |
When to call a technician
Switch the system off and book a check if a breaker trips more than once, the outdoor unit is silent, every unit shows a blinking code, or the gas has been topped up before. Book online in under a minute, or ask Luna, our AI assistant, on WhatsApp at any hour.
Frequently asked questions
Is it safe to keep running the aircons while they are not cold?
It is better not to. If the gas is low, running the compressor hard for long periods can damage it. Switch the system off and book a check.
If no leak is found, why was the gas low?
The circuit is sealed, so low gas means gas escaped at some point. Some leaks are too slow or too hidden to show on the day. If cooling drops again after a correct top-up, book a repeat leak check.
Does the warranty cover it if it happens again?
Servicing carries a 90-day warranty for water leaking or not cooling, but it excludes problems caused by a gas leak the unit already had. Repairs carry a warranty from 180 days, depending on the job.
Should I replace the whole system?
Rarely. Most shared faults, such as a tripped supply, a failed fan motor or circuit board, or low gas, can be repaired. Replacement makes sense mainly for a failed compressor on an old system.
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.
