An AC that runs but doesn't cool is the most common summer complaint in Pakistan. The good news: several causes are simple to fix yourself in minutes. Here are the eight usual culprits, from easiest to most serious — with how to check each, the fix, and when it's time to call a technician.
1. Dirty air filter (the #1 cause)
Symptom: weak airflow, room cools slowly or not at all.
How to check: open the indoor unit's front panel and look at the mesh filters — if they're grey with dust, that's your problem.
Fix: remove the filters, wash under tap water, dry fully, refit. Do this every 2–3 weeks in summer. A clogged filter alone can cut cooling dramatically.
2. Wrong mode or temperature setting
Symptom: unit runs but blows room-temperature air.
How to check: look at the remote.
Fix: set Cool mode (snowflake icon), not Fan or Dry, and set the temperature below room temperature (24–26°C is efficient). Switch fan speed to high.
3. Low refrigerant gas
Symptom: slightly cool air at best; ice or oily residue on the outdoor unit's pipes.
How to check: feel the thin copper pipe at the outdoor unit — frost or no temperature difference suggests low gas, usually from a small leak.
Fix: this needs a technician to find and seal the leak, then recharge. Topping up gas without fixing the leak just wastes money.
4. Dirty outdoor (condenser) coil
Symptom: AC cools at first, then weakens; outdoor unit feels very hot.
How to check: inspect the outdoor unit's fins for dust, leaves or bird mess.
Fix: switch off the power, gently rinse the outdoor coil with water (don't bend the fins), and keep the unit clear of walls and clutter so it can release heat.
5. Low or fluctuating voltage
Symptom: compressor won't start or cuts out, especially during peak hours.
How to check: common across Pakistan; a voltage meter or a neighbour's similar complaint confirms it.
Fix: use a good stabiliser sized for your AC, or choose a wide-voltage inverter model — see our load-shedding AC guide.
6. AC is the wrong size for the room
Symptom: cooling was always weak, even when new.
How to check: a 1-ton in a large hall will run forever and never cool.
Fix: there's no quick fix — the unit is undersized. Our load-shedding AC guide explains correct sizing, and the inverter AC price guide shows options.
7. Open room / heat gain
Symptom: AC seems fine but the room stays warm.
How to check: open doors/windows, uncovered west-facing windows, or many people/appliances in the room.
Fix: seal the room, draw curtains on sunny windows, and reduce heat sources.
8. Old, failing compressor
Symptom: frequent breakdowns, loud noises, repeated gas top-ups.
How to check: if your AC is old and needs constant repairs, the compressor may be on its way out.
Fix: repeated repair bills often cost more than upgrading. A new efficient inverter unit also slashes your electricity bill — browse the split AC range.
When to call a technician
If you've cleaned the filters and outdoor coil, confirmed Cool mode and a low set temperature, and checked voltage — and it still won't cool — it's likely a gas leak or compressor issue. Call a professional. Book a full service once before each summer plus filter cleaning every few weeks during peak use.
Two more issues worth checking
Water dripping from the indoor unit: usually a blocked or misaligned drain pipe, not a cooling fault — but it can trip the unit. Clear the drain line and make sure it slopes downward to the outside.
Remote not responding / wrong readings: replace the remote batteries, and make sure the indoor unit's temperature sensor isn't dislodged. A faulty sensor can make the AC think the room is already cool and stop cooling.
Quick diagnostic table
| Symptom | Most likely cause | First step |
|---|---|---|
| Weak airflow | Dirty filter | Wash filters |
| Cools then weakens | Dirty outdoor coil / low gas | Rinse outdoor unit |
| Blows room-temp air | Wrong mode / low gas | Set Cool mode < room temp |
| Compressor won't start | Low voltage | Add a stabiliser |
| Always cooled weakly | Undersized AC | Check ton vs room size |
Simple maintenance schedule
| How often | Task |
|---|---|
| Every 2–3 weeks (summer) | Wash indoor filters |
| Monthly | Rinse the outdoor unit, clear clutter around it |
| Before each summer | Full professional service + gas/pressure check |
How to clean your AC yourself (step by step)
Most cooling problems trace back to dirt. Here's a safe basic clean you can do in 20 minutes:
- 1. Switch the AC off at the wall — never clean a powered unit.
- 2. Open the indoor unit's front flap, slide out the mesh filters.
- 3. Rinse the filters under tap water, let them dry fully (don't refit them wet).
- 4. Wipe the indoor unit's vents with a soft, slightly damp cloth.
- 5. Outside, gently rinse the outdoor unit's fins with water — straight on, never bending them — and clear away leaves, dust and clutter.
- 6. Let everything dry, refit the filters, power on and test on Cool mode.
Leave anything involving gas, electrical parts or opening the sealed unit to a professional.
Warning signs you should call a technician
- Ice forming on the indoor coil or outdoor pipes.
- Burning smell, tripping breaker, or repeated power cut-outs.
- Loud grinding or rattling from the compressor.
- The AC needs a gas "top-up" every few months (that means a leak).
- Water leaking heavily indoors despite a clear drain.
Rough cost of common repairs
Exact charges vary by city and technician, but as a guide: a standard service/clean is the cheapest job; a gas refill (with leak repair) costs more; a PCB/control board or compressor replacement is the most expensive — sometimes enough that, on an older unit, a new efficient inverter from the split AC range makes more financial sense than repairing.
How to prevent breakdowns
Most callouts are avoidable. Wash filters every 2–3 weeks in summer, keep the outdoor unit clean and unobstructed, use a stabiliser if your voltage swings, set a sensible temperature (24–26°C), and book one professional service before each summer. This routine keeps cooling strong, bills lower, and the compressor alive for years.
Your pre-summer AC checklist
Run through this once in March–April, before the heat hits, to avoid a mid-summer breakdown when technicians are busiest:
- Wash both indoor filters and check they're undamaged.
- Rinse the outdoor unit and clear anything blocking airflow around it.
- Power on and confirm it cools quickly on Cool mode at 24°C.
- Listen for unusual noises and check the drain pipe runs water freely.
- Book a professional service if it wasn't done last year, or if cooling felt weak.
- Confirm your stabiliser works if your area has voltage swings.
Repair or replace? A simple rule
If your AC is under ~7 years old and the fault is a one-off (gas leak, capacitor, fan motor), repair it. If it's older, breaks down repeatedly, needs gas every few months, or faces a major cost like a compressor or control board, replacement usually wins — a new inverter unit also cuts your electricity bill by 30–50%, so it often pays for itself faster than you'd expect. Compare current options on the split AC range.
AC tripping the breaker?
If your AC trips the breaker or MCB, switch it off and don't keep resetting — that can cause damage. Common causes are an undersized or shared circuit, a weak/loose breaker, low voltage forcing high current, or an electrical fault in the unit. An AC should ideally run on its own dedicated circuit with a correctly rated breaker. If it trips on a proper dedicated circuit, call a technician — it points to an electrical fault that needs professional attention rather than a DIY fix.
Frequently asked questions
Why is my AC running but not cooling? Most often a dirty filter, low refrigerant gas, or a dirty outdoor coil.
How often should I clean the filter? Every 2–3 weeks during heavy summer use.
Why does my AC cool then stop cooling? Usually a dirty condenser coil or low gas — the system can't shed heat properly.
Can low voltage stop an AC from cooling? Yes — common in Pakistan; a stabiliser or wide-voltage model helps.
Is it worth repairing an old AC? If repairs are frequent, upgrading to an efficient inverter is usually cheaper over time.
Which new AC should I buy? See our Gree vs Haier vs Dawlance comparison and load-shedding AC guide.
How long should an AC last? A well-installed, well-maintained inverter AC typically lasts 8–12 years.
Does cleaning the filter really help? Yes — a clogged filter is the single most common cause of weak cooling, and washing it often restores performance straight away.