Reasons Why Your A/C Won’t Turn Off

If your air conditioner won’t stop running, it’s more than just annoying—it could signal a problem that drives up your energy bills or shortens your system’s lifespan. Here are the top reasons why your A/C won’t turn off, and when it’s time to call a professional.

1. Thermostat Set Too Low

If your thermostat is set too low, your A/C may run constantly trying to reach an unrealistic temperature—especially on hot days.

✅ Fix: Set your thermostat to a reasonable temperature (typically 72–78°F).

2. Dirty Air Filter

A clogged air filter restricts airflow, making your A/C work harder and longer to cool your home.

✅ Fix: Replace or clean your air filter every 1–3 months.

3. Frozen Evaporator Coil

Low airflow or refrigerant issues can cause the evaporator coil to freeze, preventing the system from completing its cooling cycle.

✅ Fix: Turn off the unit and let it defrost. If it freezes again, call an HVAC technician.

4. Malfunctioning Thermostat

A faulty thermostat may fail to signal your A/C to shut off when the desired temperature is reached.

✅ Fix: Test or replace the thermostat, especially if it’s older or battery-powered.

5. Fan Set to “On” Instead of “Auto”

If the fan is set to “On”, it will run continuously, even when the cooling cycle ends.

✅ Fix: Set the fan to “Auto” so it only runs during active cooling cycles.

6. Refrigerant Leak

Low refrigerant levels reduce cooling efficiency, causing your system to run nonstop to try to cool your home.

✅ Fix: This requires professional inspection and repair. Leaks should never be ignored.

7. Oversized A/C Unit

An oversized system may short cycle (turning on and off too quickly), but in some cases, it may also run too long due to poor humidity control or system inefficiency.

✅ Fix: Have an HVAC technician evaluate system sizing.

8. Faulty Relay Switch or Contactor

If the relay switch is stuck, it can keep the compressor and fan running even when the thermostat tells it to stop.

✅ Fix: This is an electrical issue that needs professional repair.

When to Call a Professional

If your air conditioner isn’t working properly, then give Air Max HVAC in Burbank a call today. We can provide help with heating and indoor air quality issues too. Our team can also perform home energy audits to make your house as efficient as possible.