AC Not Cooling – 10+ Reasons Why Your AC Is Not Cooling & How to Fix It Fast

You come home tired, switch on your AC, and expect that cold, relaxing air to hit your face — but instead, the room still feels hot. The AC is running, the fan is spinning, but cooling? Zero.
Frustrating, right?

Believe me, you’re not the only one facing this. Every day, customers from India, the USA, UAE, and Saudi Arabia call and say the same thing:
“Sir, AC is running but not cooling.”

And let me tell you something honestly —
Most of the time, the issue is not that big. But yes, ignoring it can turn a small problem into an expensive repair.

👉 Almost every AC is not cooling issue has a clear reason — and a simple solution.

In this guide, I’ll explain everything in a very easy and practical way, just like I explain to my customers during service visits.

You’ll learn the top 10 reasons why your AC is not cooling, how to check them at home, and when to call a technician.

So relax — we’ll fix this together.
Let’s start by understanding what’s really stopping your AC from cooling properly.

When your AC is not cooling, there can be many reasons behind it. But don’t worry — I’ll explain everything in the simplest way possible, just like I explain to customers during home service.

Let’s go through the top 15+ most common AC cooling problems and how you can fix them.

 1. Dirty Air Filter – The Most Common Reason Your AC Is Not Cooling

Your AC needs clean air to cool properly. But when the air filter gets dirty, dust blocks the airflow — just like when you try to breathe through a cloth. The AC keeps running, but the cool air never reaches the room.

A dirty filter can reduce cooling by 30–50%, and in many cases, it is the only reason the AC stops cooling.

Why a Dirty Filter Causes AC Not Cooling

• Air cannot pass through the evaporator coil
• Cooling coil becomes too cold and may freeze
• Compressor has to work harder
• AC blows warm or low airflow air

 How to Fix It

This is the easiest fix — you can do it yourself in just 5 minutes.

Steps:

1. Switch off the AC and disconnect power
2. Open the indoor unit front panel
3. Carefully remove the air filters
4. Wash them under running water
5. Let them dry completely
6. Reinstall the filters

How Often Should You Clean the Filter?

• Every 15 days in dusty areas (India, UAE, Saudi Arabia)
• Every 30 days in cleaner environments (USA, offices, low dust homes)

When to Call a Technician

• If filters are damaged
• If dust reached the cooling coil
• If after cleaning the filter, cooling is still low 

2. Low Refrigerant Gas – Cooling Drops Immediately

Your AC cools the air using a special gas called refrigerant gas (also known as AC gas or Freon).
If this gas becomes low, the AC simply cannot produce cold air — no matter how long you run it.

Low gas always shows this pattern:

• First, cooling reduces
• Then airflow becomes normal, but not cold
• Eventually, the AC runs without cooling at all

Why Does Refrigerant Gas Become Low?

Refrigerant gas doesn’t “finish” like fuel. It only reduces when there is a leak.

Common leak points:

• Copper pipe joints
• Indoor coil leakage
• Outdoor coil corrosion
• Vibrations causing micro leaks
• Installation mistakes

Signs Your AC Has Low Gas

You might notice:

• AC running but not cooling
• Ice forming on the indoor unit
• Hissing sound near the indoor or outdoor unit
• AC takes too long to cool
• Electricity bill goes up
• Compressor overheats and shuts down

How to Fix Low Gas Issue

You cannot fix this yourself — this needs a professional technician.

Here’s what the technician will do:

1. Check AC pressure using gauges
2. Inspect the entire line for leaks
3. Repair or weld the leak
4. Vacuum the system to remove moisture
5. Recharge the gas to the exact required level

Important Note

❗ Only refilling gas without fixing the leak will cause the same problem again.
Many people refill gas every 3–4 months because the leak was never repaired.

3. Dirty Condenser Coil – Outdoor Heat Not Releasing

Your AC has one very important job:
👉 Take the heat from inside your room and throw it outside.

And this job is done by the outdoor unit condenser coil.

But when the condenser coil becomes dirty or blocked, the outdoor unit cannot release heat.
So what happens?

The heat stays inside the system → your AC keeps running → but cooling becomes very weak or stops completely.

Why the Condenser Coil Gets Dirty

Especially in countries like India, UAE, Saudi Arabia, the outdoor unit faces:

• Dust
• Sand
• Pollution
• Traffic smoke
• Construction dust

All this settles on the coil like a thick blanket.

What Happens When the Condenser Coil Is Dirty

A dirty outdoor coil causes:

• Compressor overheating
• High electricity bills
• Weak cooling
• AC shutting down suddenly
• Inverter AC working continuously without cooling

It’s like trying to cool your room while someone wrapped the outdoor unit in a blanket — impossible.

Signs Your Condenser Coil is Dirty

You may notice:

• Outdoor unit very hot to touch
• AC takes too long to cool
• Warm air coming from indoor unit
• Outdoor fan running loudly
• Compressor turning on/off repeatedly

How to Fix It

You should not clean the outdoor coil with normal water pressure from a bucket.
It needs proper jet pressure cleaning.

A technician will:

1. Open the outdoor unit panel
2. Spray coil-cleaning chemical (if required)
3. Jet-wash the coil thoroughly
4. Clear dust from the fan and motor
5. Check gas pressure afterward

Important Safety Note

Please don’t try to clean the outdoor unit yourself, especially if it’s installed:

• On a building wall
• On a height
• In a risky location

I’ve seen many homeowners try to clean it and face accidents. Leave it to professionals.

How Often Should You Clean the Outdoor Unit?

• Every 6 months – High-dust areas
• Every 4 months – Middle East (due to sand)
• Yearly once – Low dust areas

4. Faulty Capacitor – Compressor Won’t Start

Your AC’s compressor and fan motor need a little push to start. That push is given by a small part called the capacitor.

Think of the capacitor like the “starter” of your AC.
If the capacitor becomes weak or faulty, the compressor won’t start — and if the compressor doesn’t start, cooling will never happen.

Signs of a Faulty Capacitor

You may notice:

• AC is ON but air is not cold
• Outdoor unit fan runs, but compressor stays silent
• Humming sound from the outdoor unit
• AC starts and then stops
• Ice forming on the copper pipe
• Cooling comes and goes randomly

Why Does the Capacitor Fail?

Capacitors are sensitive parts. They can fail due to:

• High temperature (India, UAE, Saudi Arabia heat)
• Voltage fluctuations
• Poor-quality capacitor installed
• Dust inside the outdoor unit
• Long-term wear & tear

If your area has frequent power cuts or voltage changes, the capacitor’s life reduces very quickly.

What Happens When the Capacitor Fails?

• Compressor won’t start
• Cooling drops to zero
• Outdoor unit overheats
• AC consumes more electricity
• Gas pressure drops abnormally

Can You Check or Fix It Yourself?

No, capacitors store electrical charge and can be dangerous.
You should never touch or open the capacitor yourself.

How a Technician Fixes It

The technician will:

1. Open the outdoor unit
2. Use a multimeter to test the capacitor
3. Check the microfarad (µF) rating
4. Replace it if it is weak/faulty
5. Restart the AC and check compressor amps and pressure

Typical Replacement Cost (Approx.)

Cost may vary depending on the AC model (Split / Window / Inverter).

5. Weak or Failed Compressor – No Cooling at All

Weak or Failed Compressor – No Cooling at All

Let me explain this in a very simple way…

Your AC’s compressor is like the heart of the cooling system. Just like the heart pumps blood in your body, the compressor pumps refrigerant gas in the AC. If the compressor becomes weak, cooling will reduce. If the compressor fails completely, there will be no cooling at all — even if your AC is running.

Signs of a Weak or Failed Compressor

If your compressor is failing, you may notice:

• AC is ON, but air is warm
• Outdoor unit fan works, but compressor stays OFF
• Burning smell from outdoor unit
• Frequent tripping (AC turns OFF suddenly)
• Loud humming or clicking noise from outdoor
• Copper pipes not getting cold
• Circuit breaker trips again and again

Why Does the Compressor Fail?

A compressor usually fails because of long-term issues, such as:

• Low refrigerant gas (running AC with low gas damages compressor)
• Dirty condenser coil (overheating)
• Faulty capacitor
• Blocked refrigerant lines
• Electrical issues
• Poor maintenance
• Overuse in very high temperatures (India, UAE, Saudi Arabia summer)

What Happens When the Compressor Fails?

• AC runs but no cooling at all
• Electricity bill goes high
• No temperature drop even after 2–3 hours
• Outdoor unit becomes extremely hot
• AC shuts down to protect itself

Can You Fix a Compressor Yourself?

No.
This is one of the most technical parts of the AC. It requires proper tools, gauges, and experience.

Trying to repair it yourself can cause:

• Electric shock
• Gas leakage
• System damage worth thousands

How a Technician Fixes It

The technician will:

1. Check compressor amps
2. Check gas pressure
3. Test capacitor
4. Inspect wiring and overload protector
5. Determine if compressor is weak, stuck, or completely dead

If the compressor is stuck, the technician may attempt:

• Hard-start kit
• Capacitor boost
• Overload reset

If the compressor is beyond repair, then replacement is required.

Approximate Compressor Replacement Cost

(Cost depends on AC type: 1 Ton / 1.5 Ton / Inverter / Non-Inverter)

When to Call a Technician

Call immediately if:

• AC blows warm air
• Compressor not turning on
• AC trips again and again
• Burning smell near outdoor unit

A weak or failed compressor is serious — but catching the problem early can save you from expensive repairs.

H3: 6. Blocked Outdoor Unit – No Ventilation Space

Your AC’s outdoor unit needs fresh air to work properly. This outdoor unit throws the hot air outside, and that’s how your room becomes cool.

But when the outdoor unit is blocked, covered, or placed in a very tight space with poor ventilation, the hot air has no place to escape.

And when heat cannot escape…
👉 Cooling stops inside the room.

Common Reasons the Outdoor Unit Gets Blocked

• Installed inside a closed balcony
• Placed in a box-like structure
• Surrounded by walls from all sides
• Garden, plants, or cloths blocking airflow
• Construction materials kept near the unit
• AC installed in a shaft with no fresh air
• Covers or cages blocking the coil

What Happens When Ventilation is Blocked

If the outdoor unit can’t breathe:

• Compressor overheats
• Cooling reduces drastically
• AC takes too long to cool
• Electricity bill increases
• AC may shut down frequently
• Gas pressure rises abnormally
• Long-term compressor damage

Your AC needs open space — at least 2–3 feet of clearance around the outdoor unit.

Signs Your Outdoor Unit Is Suffocating

You might notice:

• AC cooling very slowly
• Outdoor unit extremely hot
• Warm air blowing from indoor unit
• Compressor tripping again and again
• AC running continuously without cooling
• Unusual buzzing noise from the outdoor unit

How to Fix a Blocked Outdoor Unit

Here is what you can do right now:

• Remove any objects blocking airflow
• Make sure plants, covers, or nets are not touching the unit
• Check if the balcony door or shaft door is closed
• Ensure there is at least 2–3 feet of open space around the outdoor unit

If Outdoor Unit Is Installed in a Tight Space

You may need:

• A ventilation fan
• Extra space opening
• Louvers for airflow
• Repositioning the outdoor unit

Sometimes, shifting the outdoor unit to a better location can double the cooling efficiency.

When to Call a Technician

Call a technician if:

• You can’t access the outdoor unit
• Unit is installed on a building wall
• There is wiring or pipe adjustments needed
• Compressor keeps overheating

A technician will check:

• Airflow
• Pressure
• Compressor temperature
• Proper ventilation requirements

H3: 7. Wrong AC Mode – AC Not Cooling Due to Incorrect Settings

Believe me, this is one of the most common and funniest reasons I see at customer homes.

But when I check the remote…
AC is running in the wrong mode — usually Fan Mode, Dry Mode, or Eco Mode.

And because of this, the AC stops cooling properly.

Let me explain it in a very simple way…

❌ If AC is in FAN Mode

The AC will only blow air, not cool.
It’s like running a table fan.

❌ If AC is in DRY Mode

The AC removes humidity, but cooling reduces by 60–70%.
This mode is not for cooling the room.

❌ If AC is in ECO Mode

The AC limits compressor power to save electricity.
This reduces cooling especially in hot countries like India, UAE, Saudi Arabia.

❌ If AC is in HEAT Mode (Inverter AC)

Your AC will blow hot air, not cold air.

Many customers accidentally turn ON Heat mode in winter and forget to change it.

✔ The Correct Mode for Maximum Cooling: COOL Mode

Always make sure the AC is in COOL (Snowflake ❄️) Mode.

When AC is in COOL mode:

• Compressor works properly
• Maximum cooling is delivered
• Temperature control works correctly
• Airflow remains strong

Signs That AC Is in the Wrong Mode

• AC blowing warm air
• Cooling is very slow
• Fan speed high but no cooling
• Compressor not turning ON
• Room not cooling even after 1–2 hours

How to Fix This (Very Easy)

You can fix this in 5 seconds:

1. Pick up your AC remote
2. Press the MODE button
3. Change the mode to COOL (❄️)
4. Set temperature to 24°C
5. Keep fan speed on AUTO

That’s it!
In many homes, the AC starts cooling immediately after this.

When to Call a Technician

Call a technician only if:

• AC is in COOL mode but still not cooling
• Compressor not turning ON
• Cooling is extremely slow
• AC remote not working properly

Otherwise, this is one problem you can solve yourself

H3: 8 – Undersized AC – Wrong AC Ton for Room Size

Simple Explanation

A 1 Ton AC is designed to cool 1 Ton space only.
A 1.5 Ton AC can cool a bigger room, and so on.

But when a small AC is installed in a big room, the AC keeps running nonstop…
…and still the room doesn’t cool.

It’s like trying to cool a hall with a small table fan — not possible.

Why Undersized AC Causes AC Not Cooling

When AC tonnage is less:

• Room never reaches set temperature
• Compressor keeps running continuously
• Electricity bill becomes very high
• Cooling is slow or almost zero during peak heat
• AC gets overheated and parts wear out faster
• Compressor gas pressure becomes unstable

An undersized AC is always overworked, so cooling automatically drops.

How to Know If Your AC Size Is Wrong

Here are the signs you’ll notice:

• AC runs for hours but still no cooling
• Only the area near AC feels slightly cool
• Room takes forever to cool
• AC turns ON/OFF frequently
• Temperature doesn’t drop even at night
• You need to set temperature to 16°C to feel cool
• AC air feels cool but room stays warm

If these signs match… your AC is likely too small for your room.

Correct AC Size for Room (Ton vs. Room Size Chart)

Important Factors That Increase Cooling Load

If any of these conditions exist, you need bigger AC:

• Top floor room
• Large windows
• Direct sunlight
• Room facing west
• High ceilings
• Multiple people in the room
• Electronic devices (PC, fridge, lights)

Recommendation

We recommend a 1.5 Ton Inverter AC.
After installation, cooling became perfect.

How to Fix Undersized AC Problem

✔ Option 1: Upgrade the AC

The best long-term solution is to install:

• 1.5 Ton AC (if room is medium)
• 2 Ton AC (if room is large or top floor)

This saves electricity and improves cooling.

✔ Option 2: Add Second AC

For large halls, adding a second AC gives better results.

✔ Option 3: Reduce Heat in Room

You can improve cooling by:

• Using blackout curtains
• Keeping doors closed
• Turning lights off
• Installing shade for windows
• Reducing sunlight
• Adding insulation

✔ Option 4: Use high-capacity Inverter AC

Inverter AC automatically boosts compressor speed in extreme heat.

When to Call a Technician?

If you’re unsure about:

• Your room size
• AC ton capacity
• Whether your AC is undersized

A technician can measure:

• BTU requirement
• Heat load
• Sunlight direction
• Room insulation

This ensures your room gets the perfect AC size

H3: 9 – Poor Room Insulation – Heat Entering Continuously (Major Reason for AC Not Cooling)

Let me explain this in a simple, customer-friendly way…
Even if you have a powerful AC, poor room insulation can completely destroy your cooling.
And then people say — “My AC is not cooling properly!”

But the truth is:
If heat is continuously entering your room, your AC can NEVER cool it properly.

How Poor Insulation Causes AC is Not Cooling

When a room is not properly insulated, heat keeps coming inside through:

• Cracks in walls
• Gaps around windows
• Sunlight directly entering the room
• Thin walls that absorb heat
• No ceiling insulation
• Door bottom gaps

Because of this, the AC has to work 3× harder, yet cooling still remains weak.

Even the best AC cannot fight against continuous heat entry.

Common Symptoms of Poor Room Insulation

• AC runs but room never gets fully cool
• Compressor runs almost continuously
• Cooling uneven (one area cool, another still hot)
• Room heats up quickly after turning off AC
• Electricity bill becomes very high

These are clear signs that your room is losing cooling faster than the AC can produce.

How to Fix Poor Insulation (Simple & Budget-Friendly Tips)

1. Use Thick or Blackout Curtains

Blocks direct sunlight and instantly improves cooling by 20–30%.

2. Seal All Window & Door Gaps

Use:

• Rubber sealing strips
• Door bottom sweepers
• Silicone sealant

Very cheap, very effective.

3. Apply Heat-Proof / Exterior Insulation Paint

Reduces outside wall temperature by 8–12°C.

4. Install Reflective Window Films

Blocks heat while allowing light to enter.
A great solution for west-facing rooms.

5. Add Thermocol / Foam Insulation on the Ceiling

Affordable DIY option and significantly reduces heat transfer.

6. Use Carpet or Rug on Tiled Floors

Tiles absorb heat. Carpets help reduce heat entering from the floor.

7. Consider a False Ceiling

Reduces the room’s heat load and improves cooling quickly.

Final Advice

If your room is poorly insulated, AC servicing or gas refilling will not solve the problem.
You must reduce heat entering the room.

Once the insulation is fixed, your AC will cool faster, smoother, and more efficiently

H3: Ice Formation on Evaporator Coil – Airflow Obstruction (Major Reason for AC Not Cooling)

Let me explain this in a simple, customer-friendly way….

When ice forms on the evaporator coil, it looks like your AC is “overcooling”, but in reality, it is a serious cooling problem. A frozen coil means the AC is unable to absorb heat properly and that’s why your AC stops cooling the room.

Why Does Ice Form on the Evaporator Coil?

Ice formation happens when airflow is restricted or the refrigerant cycle is disturbed. This causes the coil temperature to drop below freezing, turning moisture into ice.

Here are the most common causes:

1. Dirty or Choked Air Filter

Low airflow = coil gets too cold = ice forms.

2. Low Refrigerant Gas Level

When gas is low, pressure drops → coil temperature falls → ice buildup.

3. Blocked or Slow Blower Fan

If the blower cannot push air properly, coil will freeze.

4. Clogged Evaporator Coil

Dust stuck on the coil prevents airflow and causes freezing.

5. Thermostat Fault

Incorrect temperature readings can make the system overcool.

6. Closed or Blocked Vents

Stops air circulation inside the room.

7. AC Running in Very Low Temperature

Running AC below 18°C for long hours can trigger coil freezing.

Signs Your Evaporator Coil Has Ice Formation

You will notice:

• Weak airflow from AC
• Water dripping or leakage from indoor unit
• Room not cooling
• Loud hissing or bubbling sound
• AC turning on & off (short cycling)
• Visible frost on indoor coil or copper pipes

How to Fix Ice Formation on Evaporator Coil (Step-by-Step)

Step 1: Turn Off the AC Immediately

Running it will damage the compressor.

Step 2: Run the AC in Fan Mode

This helps melt the ice faster (usually 20–60 minutes).

Step 3: Check & Clean the Air Filter

Dirty filter is the #1 reason for ice formation.

Step 4: Ensure Vents Are Open

Make sure nothing is blocking airflow.

Technical Fixes (Needs a Technician)

1. Gas Pressure Check & Refilling

If refrigerant is low, coil will freeze again.

2. Deep Coil Cleaning

Indoor evaporator coils must be cleaned properly.

3. Blower Motor Check

If the blower is slow or faulty, airflow gets restricted.

4. Thermostat Sensor Adjustment

Technician ensures accurate temperature reading.

5. Check for Refrigerant Leakage

Small leaks lead to recurring freezing problems.

How to Prevent Ice Formation in the Future

• Clean filters every 15–30 days
• Don’t run AC below 20–22°C continuously
• Annual servicing with coil cleaning
• Ensure no furniture blocks airflow
• Monitor indoor humidity levels
• Fix refrigerant leaks as soon as possible

When Should You Call a Technician?

Call immediately if:

• Ice returns again after cleaning
• Cooling is almost zero
• Water is leaking from indoor unit
• There is a refrigerant leak suspicion
• Blower fan speed is low

This is one issue that can shorten compressor life, so don’t delay.

H2: Conclusion

Fix Your AC Not Cooling Issue Before It Gets Worse

I hope by now you clearly understand why your AC is not cooling and what you can do to fix it quickly.
Most cooling problems start small — like a dirty filter, blocked outdoor unit, or low gas —
but if ignored, they can turn into major repairs like compressor failure or heavy electricity bills.

Your AC is just like your car…
Regular maintenance = Long life + Better performance + Less repair cost.

So don’t wait for the AC to stop cooling completely.
A small issue fixed today can save you from a big expense tomorrow.