Why Your AC Is Too Cold Even at 28°C — The Silent Sensor Failure Problem

Setting your air-conditioner to 28°C is supposed to make the room comfortable, energy-efficient, and pleasant—especially in Singapore’s hot and humid climate.But what if the opposite happens?

The room turns freezing cold, the air-con never seems to stop, and your electricity bill quietly climbs higher every month.

Most people assume this means their air-conditioner is “powerful” or “cooling well.”In reality, this is often a hidden system fault—and one of the most commonly ignored ones:

👉 A failing temperature sensor (thermistor).

This single component, when faulty, can silently damage your system, waste electricity, and shorten the lifespan of expensive parts like the compressor and PCB.

Let’s break down what’s really happening.

How Your Air-Conditioner Knows When to Stop Cooling

Every modern air-conditioning system relies on a temperature sensor, also called a thermistor, usually located inside the indoor unit.

Its job is simple but critical:

·         Detect the actual room temperature

·         Send real-time feedback to the control board

·         Tell the compressor when to start, slow down, or stop

When the sensor works correctly:

·         You set 26–28°C

·         The room reaches that temperature

·         The compressor cycles off

·         Comfort is maintained with minimal energy use

When the sensor fails, everything goes wrong—quietly.

What Happens When the Sensor Fails

A faulty sensor sends wrong temperature data to the system.

The AC may think:

·         The room is still hot (even when it’s already cold)

·         Cooling demand is still high

·         The compressor must continue running

As a result:

·         The AC overcools

·         The compressor runs continuously

·         The room becomes uncomfortable

·         Power consumption spikes

And the worst part?⚠️ There is often no error code.

So users continue running the system, unaware that damage is accumulating day after day.

Common Signs of AC Sensor Failure

Many customers call for help only after months of discomfort and high bills.Here are the warning signs you should never ignore:

·         ❄️ Room feels freezing even at 27–28°C

·         🔁 AC never cuts off

·         🌡️ Temperature feels inconsistent

·         💸 Electricity bill increases without usage change

·         🤧 Cold drafts causing discomfort or sickness

·         🧠 No fault code, but “something feels wrong”

If two or more of these apply, sensor failure is highly likely.

Why This Problem Is So Common in Singapore

Sensor issues are especially widespread in Singapore due to local conditions:

🌡️ High Humidity

Moisture accelerates sensor degradation and corrosion.

🕒 Long Operating Hours

Many systems run 8–16 hours daily, stressing components.

🌫️ Dust & Grease Build-Up

Sensors covered in dust read temperatures inaccurately.

🏢 Aging Systems

Older air-cons often have drifting or unstable sensors.

Because sensor failure is gradual, most people adapt to the cold instead of fixing the root cause.

The Real Damage You Don’t See

Running an AC with a faulty sensor doesn’t just make you uncomfortable—it causes long-term damage.

🔴 Compressor Overwork

Continuous operation shortens compressor life dramatically.

🔴 PCB Stress

Control boards overheat and fail due to nonstop demand signals.

🔴 Energy Waste

Your AC consumes far more electricity than necessary.

🔴 Higher Repair Costs Later

A simple sensor replacement today can prevent a full system breakdown tomorrow.

In many cases, customers only discover the sensor issue after replacing expensive parts unnecessarily.

Why “Just Lower the Fan Speed” Doesn’t Fix It

Some users try quick fixes:

·         Lowering fan speed

·         Changing swing direction

·         Adjusting set temperature repeatedly

These don’t solve the problem because:👉 The AC still believes the room is hot.

Until the sensor feedback is corrected, the system will continue forcing cooling regardless of settings.

Proper Diagnosis: What a Professional Should Do

A proper sensor check is not just visual.

It involves:

·         Measuring sensor resistance

·         Comparing readings with actual room temperature

·         Checking sensor placement and insulation

·         Verifying communication with the PCB

·         Testing system cycling behaviour after calibration

Skipping these steps leads to misdiagnosis—and wasted money.

The Correct Fix (And It’s Usually Simple)

In most cases, the solution is straightforward:

✅ Sensor inspection & testing✅ Sensor replacement if readings are inaccurate✅ System recalibration✅ Operational testing under real conditions

When done early, this:

·         Restores comfort

·         Reduces electricity bills

·         Protects compressor & PCB

·         Extends system lifespan

It’s one of the highest-value, lowest-cost fixes in air-conditioning maintenance.

Why Early Action Saves You Money

Many customers delay repairs because the AC is “still cooling.”

But cooling is not the same as correct operation.

Fixing a sensor early can:

·         Save hundreds of dollars in power bills annually

·         Prevent thousands in major repairs

·         Improve daily comfort immediately

Ignoring it is far more expensive.

Final Thought: Cold Is Not Always Good

If your air-conditioner feels too cold at high settings, don’t assume it’s normal.

That discomfort is your system’s early warning sign.

The longer it runs this way, the more damage it does—silently.

📞 Call / WhatsApp: +65 8151 8857🌐 Website: www.aotrinitysg.com.com

Alpha & Omega Trinity Pte LtdAir-Conditioning • Sensors • Preventive Maintenance • Singapore