AC Not Turning On in Kolkata? 10 Causes & Fixes (2026)

South and Central Kolkata experience significant voltage fluctuations every summer — especially between 2 PM and 8 PM when the CESC grid is under peak load. When voltage drops suddenly or spikes, the AC's dedicated MCB (miniature circuit breaker) trips automatically to protect the unit. This is a safety feature, not a fault.

A dead or faulty remote is far more common than people realise — especially for ACs that were switched off over winter and stored with old batteries. In Kolkata's humid climate, battery terminals inside remotes corrode faster than in drier cities, causing poor contact even when the batteries are not completely dead.

The capacitor provides the burst of power needed to start the compressor and fan motors. When the capacitor weakens or fails — which happens much faster in Kolkata due to voltage fluctuations and 7-month continuous operation — the motors cannot start. The AC may hum when you try to turn it on, but nothing else happens.

Capacitor failure is one of the most common AC faults we see in Kolkata homes after the 3 to 4 year mark. It is a quick fix — a technician replaces the capacitor in 20 to 30 minutes.

The PCB (printed circuit board) is the brain of a modern inverter AC — it controls everything from startup sequences to temperature regulation. When the PCB is damaged by a voltage spike — very common in Kolkata during pre-monsoon thunderstorms and summer peak hours — the AC may show no response at all, or show error codes on the display.

The compressor has a built-in thermal overload protector — when it overheats, this safety switch cuts power to the compressor to prevent permanent damage. In Kolkata, this happens most often when the outdoor unit is blocked in a tight balcony with poor ventilation, causing the compressor to run at extreme temperatures during the 40°C May–June heat.

When the thermal overload trips, the AC may appear completely dead or only the fan runs while the compressor is off. The AC often recovers on its own after 30 to 60 minutes of cooling down — but if this happens regularly, it means your outdoor unit ventilation needs to be improved.

Many modern ACs have a float switch — a safety mechanism that shuts the AC off completely if the drain pan fills with water. This happens when the drain pipe is blocked and water backs up into the pan. In Kolkata during monsoon, this is very common because algae blocks drain pipes quickly and the AC produces extra condensation in the high humidity.

If the AC runs for a while and then shuts itself off completely and will not restart for an hour or two, a frozen evaporator coil is the likely cause. Low refrigerant gas or a severely blocked filter causes the evaporator coil temperature to drop below freezing — the entire coil ices over, airflow stops, and the AC's safety system shuts it down.

The thermostat senses room temperature and tells the compressor when to start. If the thermostat is faulty, it may never send the start signal — the AC display works, the fan may run, but the compressor never kicks on and the AC does not actually cool or operate normally. In Kolkata's humidity, the temperature sensor inside the indoor unit can also develop moisture-related faults.

Power cord damage — from rats, moisture, or physical wear — can completely cut power to the AC. In Kolkata's older homes and buildings, internal wiring deterioration is also a common cause of ACs suddenly losing power. Monsoon season accelerates wiring corrosion at connection points, particularly in outdoor unit wiring that faces direct rain exposure.

Very common in Kolkata at the start of every summer — an AC that was switched off from November to March is started up for the first time in April and does not respond. In most cases the cause is simply dead remote batteries combined with an MCB that was left in the off position after the last season. In some cases, dust-seized fan bearings or capacitor degradation over the off-season can also prevent startup.