Why is your aircon not cold?
Is your aircon running, humming away, and still blowing lukewarm air? On a hot Jurong afternoon, that’s hard to ignore.
Most aircon not cold repair jobs come down to one of three problems. Air isn’t passing over the coil properly, there isn’t enough refrigerant, or a part that controls cooling has failed. We find which one it is before you pay for anything.
Here’s a simple benchmark we use. PICKHVAC explains that a healthy system cools the air by about 15 to 20°F (roughly 8 to 11°C) between the air going in and the air coming out. A much smaller gap tells us something is wrong.
On every not-cold visit, we check:
- Airflow from the indoor unit and the condition of the filter and evaporator coil
- The delta-T temperature test, which compares the air going in with the air coming out
- Refrigerant pressure at the outdoor condenser unit
- The compressor, outdoor fan and capacitor
- The thermistor sensors and the PCB control board
Repair starts from S$60. You get a fixed quote before any work starts.
Common causes we find in Jurong homes
| Cause | Typical sign | Usual fix |
|---|---|---|
| Dirty coil and blower | Weak airflow even on high fan | Chemical wash, from S$80 per unit |
| Low refrigerant from a leak | Ice on the copper pipe, hissing sound | Leak check and gas top-up, from S$80 |
| Failed capacitor, sensor or PCB | Outdoor unit not running, cold then warm | Part repair, from S$60 |
Dirty coil and blower
This is the most common cause, and the cheapest to fix. When the coil fins are packed with dust, air can’t pass through and the room never cools. Regular general aircon servicing every 3 to 4 months stops it building up in the first place.
If the coil is badly fouled, a chemical wash from S$80 usually brings the cooling back. A quick clue: if airflow feels weak even on high fan, the filter or coil is the first place we look.
Low refrigerant from a leak
Refrigerant runs in a sealed loop. If the pressure is low, there’s a leak somewhere, often at a flare joint.
Signs to watch for:
- Icing on the copper pipe
- A hissing sound
- Cooling that fades over weeks
Most newer units use R32 refrigerant. The aircons.sg blog notes it has replaced R410A in most new Singapore units sold since 2019. Older units use R410A or R22, and R22 has been phased out under the Montreal Protocol because it harms the ozone layer.
This matters for your wallet. Topping up a leaking system without fixing the leak just means the gas escapes again, so we find the leak before any gas top-up.
Failed capacitor or fan
If the outdoor unit hums but doesn’t start, or the fan doesn’t spin, a weak capacitor is a frequent culprit. Snowflake Aircon points out that a steady hum with no fan rotation means the motor is getting power but can’t start.
A weak capacitor can look like a dead compressor, yet it costs a fraction to replace. So get it tested before agreeing to any big-ticket quote. It’s a small part and usually a quick repair.
Sensor or control board faults
A thermistor is a small temperature sensor. If it’s faulty, it can tell the unit the room is already cold, so cooling stops early.
A failing PCB control board can stop the outdoor unit altogether. We test both before replacing anything.
One room cold, another not
On a multi-split system, each fan coil is separate. One room can be warm while the others are fine, and the cause is usually one of three things on that line:
- A dirty coil
- A failed sensor
- A refrigerant issue
We test the problem fan coil on its own. Our guide to servicing inverter multi-split systems explains how these set-ups work.
Should you wait?
Not for long. A unit that isn’t cooling makes the compressor work harder for longer, and that pushes up your electricity bill. Saces estimates that aircon makes up roughly 36% of household electricity in Singapore, so a struggling unit costs you every month.
If you see ice on the pipes, do this:
- Switch the unit off at the remote or wall controller.
- Let the ice thaw fully.
- Book your aircon not cold repair visit.
Trane advises switching a system with a frozen coil to OFF, because running it that way can cause major damage. We offer same-day slots in Jurong, subject to availability. Book a visit and we’ll sort out why your aircon isn’t cold, with a fixed quote before we touch a thing.
