Your AC is running, the compressor is on, the fan is blowing — but the room is still warm. In Kolkata's summer, where temperatures cross 38°C and humidity makes it feel like 45°C, a non-cooling AC is not just uncomfortable. It is unbearable.
The good news: most of the time, the reason your AC is not cooling in Kolkata is something that can be diagnosed and fixed the same day. This guide walks you through all 7 common causes — and tells you exactly what to do about each one.
We are
Unique Aircon — a certified AC repair team based in Jadavpur, serving South and Central Kolkata for 9+ years. If your AC is not cooling and you need same-day help,
book a service visit here or call
+91 83469 04100.
Quick Self-Check Before Calling a Technician
Before we go into the 7 causes, run through this 2-minute checklist yourself. Sometimes the fix is simpler than you think:
☐
Is the AC set to Cool mode? Not Fan-only or Dry mode? Check the remote — the mode icon should show a snowflake.
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Is the set temperature lower than the room temperature? If the room is 34°C and the AC is set to 36°C, it will not cool.
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Are all doors and windows closed? In Kolkata's humidity, even one open window completely defeats the AC.
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Is the outdoor unit running? Go outside and check if the fan on the outdoor unit is spinning. If it is not, the compressor may have tripped.
If all of the above are fine and the AC is still not cooling — read on. One of the 7 reasons below is almost certainly the cause.
7 Reasons Your AC is Not Cooling in Kolkata
1
Low Refrigerant Gas (Most Common Cause)
Refrigerant — also called AC gas — is the substance that absorbs heat from your room and releases it outside. If the gas level is low due to a leak, your AC will blow air but will not cool the room effectively.
This is the single most common reason ACs stop cooling in Kolkata, especially in older units or those that have not been serviced in 2–3 years.
Signs of low gas: Ice forming on copper pipes · Hissing sound from the unit · AC cools for 10 minutes then stops · Outdoor unit running but no cold air inside
What to do: Call a certified technician to check gas pressure with a manifold gauge. If gas is low, the leak must be found and repaired before refilling. See our
AC gas charging cost guide for Kolkata to understand what this will cost.
2
Dirty or Blocked Air Filter
The air filter in your indoor unit collects dust, pet hair, and debris with every cycle. In Kolkata — where construction dust, monsoon humidity, and pollution are constant — filters clog faster than in most cities.
A blocked filter restricts airflow over the evaporator coil, drastically reducing cooling efficiency. Your AC works harder, consumes more electricity, and still cannot cool the room properly.
What to do: Open the indoor unit's front panel, slide out the filters, and rinse them under running water. Let them dry fully before reinserting. Do this every 3–4 weeks during summer. If the filter is torn or damaged, replace it. A basic AC filter costs ₹150–₹400 in Kolkata.
3
Dirty Evaporator or Condenser Coils
Even if your filter is clean, dust and grime can settle directly on the evaporator coil (inside unit) and the condenser coil (outside unit) over time. This creates an insulating layer that prevents proper heat exchange — meaning the AC cannot absorb heat from inside your room or release it outside.
In Kolkata's dusty and humid climate, coils can get dirty enough in a single summer to reduce cooling by 20–30%.
What to do: Coil cleaning requires a technician with a fin comb and coil cleaning spray. Do not attempt to clean condenser coils yourself. Annual professional cleaning before summer — typically March or April — prevents this completely.
The compressor is the heart of your AC — it pressurises the refrigerant and drives the entire cooling cycle. If the compressor is weak, failing, or has tripped due to overheating, the AC will run but produce no cold air at all.
Compressor problems are more common in Kolkata during peak summer (May–June) when ACs run for 18–20 hours a day without rest, causing the unit to overheat repeatedly.
Signs of compressor failure: Outdoor unit fan spinning but no cooling · Loud clicking or rattling sound from outdoor unit · AC trips the circuit breaker repeatedly · Unit runs for 2–3 minutes then shuts off
What to do: This requires a technician. Compressor repair or replacement in Kolkata costs ₹6,000–₹18,000 depending on brand and tonnage. Do not ignore this — a failing compressor can damage other components if left running.
5
Outdoor Unit Blocked or Overheating
The outdoor unit releases the heat absorbed from inside your room. If it is surrounded by walls, covered with a cage or cloth, placed in direct sunlight without ventilation, or blocked by vegetation — it cannot release heat efficiently and cooling drops sharply.
This is very common in Kolkata flats where outdoor units are installed on narrow balconies, inside grilles, or in enclosed shafts with poor airflow.
What to do: Ensure at least 30–45 cm of clear space around all sides of the outdoor unit. Remove any covers or decorative grilles. If the unit is in direct sunlight all day, a small shade (not enclosure) above it can reduce the heat load significantly.
6
AC Undersized for the Room
A 1-ton AC in a 200 sq ft room will struggle on a 40°C Kolkata afternoon — especially if the room has a west-facing window, a tin roof, or is on the top floor. The AC is not broken; it is simply not powerful enough for the heat load.
Many Kolkata homes were fitted with ACs before additional floors were added or before large glass windows became common. The old tonnage is no longer adequate.
General rule for Kolkata: 1.0 ton for rooms up to 120 sq ft · 1.5 ton for 120–180 sq ft · 2.0 ton for 180–240 sq ft. Add 0.5 ton if the room has a west-facing wall, large windows, or is on the top floor under a concrete roof.
7
Faulty Thermostat or PCB Board
The thermostat senses room temperature and tells the compressor when to switch on and off. If it is faulty, the compressor may never turn on — or may shut off too early — even when the room is hot. Similarly, a damaged PCB (printed circuit board) can cause erratic behaviour including loss of cooling.
Voltage fluctuations — extremely common in Kolkata during peak summer when the grid is under load — are a leading cause of PCB and thermostat damage.
Signs: AC turns on and off randomly · Remote functions work inconsistently · AC runs but compressor never kicks in · Error codes flashing on the display
What to do: Use a stabiliser or voltage protector for your AC — essential in Kolkata. Thermostat replacement costs ₹800–₹2,500. PCB replacement varies by brand: ₹2,500–₹8,000. A technician can test both in a single visit.
Repair Cost Summary — AC Not Cooling in Kolkata (2026)
Here is a quick reference of what each fix typically costs in Kolkata so you are not caught off guard:
| Problem |
Typical Repair Cost (Kolkata) |
DIY Possible? |
| Low refrigerant gas |
₹1,500 – ₹4,500 |
No |
| Dirty air filter |
Free (self-clean) |
Yes |
| Dirty coils |
₹600 – ₹1,500 |
No |
| Compressor repair / replacement |
₹6,000 – ₹18,000 |
No |
| Thermostat replacement |
₹800 – ₹2,500 |
No |
| PCB board replacement |
₹2,500 – ₹8,000 |
No |
⚠ Note: Always get a written price estimate before any repair begins. At Unique Aircon, we diagnose first and quote before touching anything — no surprise bills.
How to Prevent Your AC From Stopping Cooling — Kolkata Tips
Most of the reasons above are completely preventable with basic annual maintenance. Here is what Kolkata AC owners should do every year:
✓
Get a full service done in February or March — before summer hits. This includes coil cleaning, gas pressure check, filter wash, drain cleaning, and electrical inspection. Costs ₹500–₹1,200 per unit.
✓
Clean your filters every 3–4 weeks during summer. In Kolkata's dusty pre-monsoon season (March–May), filters clog twice as fast as in winter.
✓
Install a voltage stabiliser — especially if you live in areas of South Kolkata prone to power fluctuations. A good stabiliser costs ₹1,500–₹3,500 and protects a ₹40,000 AC indefinitely.
✓
Consider an Annual Maintenance Contract (AMC) — Unique Aircon's AMC covers 2 scheduled services per year plus priority call-outs. Prevents most of the problems listed above before they happen.
Frequently Asked Questions
Q
My AC is cooling but not enough — is that the same problem?
Usually yes — partial cooling is an early sign of one of the same 7 causes above, most commonly low gas or a dirty filter. Address it early before it stops cooling entirely. Partial cooling also means the AC is overworking and consuming 20–30% more electricity.
Q
My new AC is also not cooling well. Why?
New ACs rarely have gas or mechanical issues. The most likely causes are: wrong tonnage for the room size, poor installation (incorrect pipe length or slope), blocked outdoor unit placement, or the unit running in Fan or Dry mode accidentally. Have the installer re-check the setup.
Q
How quickly can you send a technician in Kolkata?
Unique Aircon offers same-day service across South and Central Kolkata on most days. Call or WhatsApp before noon for a same-day visit. We cover Jadavpur, Garia, Tollygunge, Ballygunge, Kasba, Behala, Dhakuria, Santoshpur, and surrounding areas.
Q
Is it worth repairing an old AC or should I replace it?
A general rule: if the repair cost is more than 50% of the cost of a new equivalent AC, replacement makes more sense — especially if the unit is 8+ years old and uses R22 gas. If the repair is minor (filter, gas top-up, thermostat), fixing is almost always the better value. Our technicians will give you an honest recommendation either way.
AC Not Cooling? We'll Fix It Today.
Same-day diagnosis and repair across South & Central Kolkata. Transparent pricing, no hidden charges.
📍 3/87 C. R. Colony, Jadavpur, Kolkata – 700032
Jadavpur · Garia · Tollygunge · Ballygunge · Kasba · Santoshpur · Behala · Dhakuria · Jodhpur Park · Mukundapur · Anandapur · Sonarpur · Ruby · Bhawanipore
Last updated: June 2026 · Written by the Unique Aircon technical team, Kolkata
