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Aircon Keeps Turning On and Off? How to Fix Short-Cycling
Aircon turns on for a few minutes, shuts off, then starts again. This on-off cycling wastes electricity and wears out the compressor.
Professional service usually required
Difficulty: Medium to Hard Last updated: March 2026
What You Can Fix Yourself
What Is Short-Cycling?
Short-cycling is when your aircon compressor turns on and off in rapid cycles (every 5-10 minutes) instead of running for 15-20 minute cooling cycles. It wastes energy, increases your electricity bill, and puts excessive wear on the compressor.
In Singapore's climate, a properly functioning aircon should run for at least 15-20 minutes per cycle to effectively cool and dehumidify a room.
Clean the Air Filters
Clogged filters restrict airflow, causing the evaporator coil to freeze. The system detects this abnormal condition and shuts off as a safety measure. Once the ice melts, it starts again — creating the on/off cycle.
Clean your filters first — this solves the problem in about 30% of short-cycling cases.
Check Your Thermostat Placement
If your thermostat (or the aircon's built-in sensor) is in direct sunlight, near a heat source (lamp, kitchen, window), or blocked by furniture, it reads a higher temperature than the actual room temperature.
This causes the aircon to cycle erratically. Move heat sources away from the sensor area, or close curtains if direct sunlight hits the unit.
When to Call a Professional
Oversized or Undersized System
If your aircon was sized incorrectly for the room:
- **Oversized unit:** Cools the room too fast, shuts off, room warms up quickly, cycle repeats
- **Undersized unit:** Runs continuously but can't reach target temperature, overheats, shuts off as safety measure
In Singapore, the general guideline is:
- 9,000 BTU for rooms up to 15 sqm
- 12,000 BTU for rooms 15-25 sqm
- 18,000 BTU for rooms 25-35 sqm
- 24,000 BTU for rooms 35-50 sqm
If your unit is the wrong size, unfortunately the only fix is replacing it with a correctly sized one.
Low Refrigerant or Electrical Issues
Low refrigerant causes the system to struggle to reach temperature, triggering safety shutoffs. Electrical issues (faulty capacitor, loose connections, failing thermostat) can also cause erratic cycling.
Both require professional diagnosis and repair.
When to Call a Pro
If cleaning filters and checking thermostat placement doesn't resolve the short-cycling, call a technician. Persistent short-cycling significantly reduces compressor lifespan and increases energy costs.
Browse contractor directory →Maintenance Tip
When getting a new aircon installed, always have the contractor properly size the system for your room. Oversizing is a common mistake — bigger isn't always better.