Troubleshooting
AC Not Cooling? 9 Reasons Why and How to Fix Each One
18 June 2026 • 7 min read
Your AC runs but the room stays warm. Here are the nine causes our Nagercoil technicians see most, what each costs to fix, and what you can check yourself.
Start with the three things you can check yourself
Before booking a technician, rule out the simple causes. A surprising share of 'AC not cooling' calls in Nagercoil turn out to be a wrong mode setting, a choked filter or a blocked outdoor unit.
- Mode set to Fan or Dry instead of Cool — check the remote display.
- Filters clogged with dust — slide them out, wash and dry them.
- Outdoor unit blocked by a wall, plant or cover — it needs a foot of clear space on all sides.
Low refrigerant from a slow leak
If cooling faded gradually over weeks, a refrigerant leak is the likeliest cause. Topping up without repairing the leak is money wasted — insist on a nitrogen pressure test first, then a weighed charge.
Dirty condenser coil
Nagercoil's salt-laden coastal air coats outdoor coils faster than inland towns. A caked coil cannot reject heat, so the compressor runs continuously while the room stays warm. A jet wash usually restores full cooling the same day.
Failing capacitor or compressor
If the outdoor fan spins but the compressor hums and stops, the run capacitor is often the culprit — an inexpensive part. A genuinely seized compressor is far costlier, so always ask for winding and capacitor test readings before agreeing to replacement.
Undersized AC or heat load
A 1 ton unit in a sun-facing 180 sq ft room with a concrete roof will never hold temperature during a Nagercoil April. If the AC cools at night but not by day, tonnage rather than a fault is the problem.