Your air conditioner is running, you can hear it, but the house just won’t cool down. On a hot July afternoon, that’s the last thing you want. Here are the most common reasons, starting with the simple ones you can check yourself.
1. Thermostat settings
Make sure the thermostat is set to COOL, not HEAT or FAN, and that the temperature is set a few degrees below the room temperature. If the screen is blank, replace the batteries.
2. A dirty air filter
Your furnace filter also serves your air conditioner. When it’s clogged, too little air passes over the indoor coil. Cooling drops, and the coil can even freeze.
What to do: check the filter and replace it if it’s dirty.
3. The outdoor unit isn’t running
Go outside and check the outdoor unit. Is the fan spinning? If the indoor blower runs but the outdoor unit is silent, check the breaker in your electrical panel and the disconnect switch on the wall next to the unit.
If the breaker is fine and the outdoor unit still won’t start, the cause is often a failed capacitor or contactor. These are common parts that wear out, and replacing them is a routine repair for a technician. Don’t open the unit yourself: these parts hold a dangerous electrical charge.
4. A dirty outdoor coil
The outdoor unit releases the heat from your home. If its coil is covered in cottonwood fluff, grass clippings or dirt, it can’t release heat well, and cooling suffers.
What to do: turn off the power at the disconnect, then gently rinse the outside of the coil with a garden hose (never a pressure washer). Keep plants and fences at least 60 cm (2 feet) away from the unit.
5. A frozen indoor coil
If you see ice on the copper lines near the outdoor unit, or water around the furnace, the indoor coil may be frozen. This is usually caused by poor airflow (a dirty filter or closed vents) or low refrigerant.
What to do: turn the AC off and set the fan to ON for a few hours to melt the ice. Replace the filter. If it freezes again, call a technician.
6. Low refrigerant from a leak
An air conditioner doesn’t use up refrigerant. If it’s low, there’s a leak somewhere. Topping it up without fixing the leak only delays the problem. In Ontario, refrigerant work must be done by a certified technician.
From the field
A Richmond Hill homeowner called us on a hot July afternoon. The AC had been running all day, but the house kept getting warmer. At the outdoor unit, the compressor was humming but the condenser fan wasn’t spinning: the run capacitor had failed. We replaced it, checked the fan motor and refrigerant pressures, and the house was cooling again within the hour.
When to call a technician
Call us if the outdoor unit won’t start, if the coil keeps freezing, if you hear grinding or buzzing, or if the house still won’t cool after you’ve checked the thermostat and filter.
Air Net Heating & Air Conditioning repairs central air conditioners across Richmond Hill and York Region, all major brands, with upfront flat-rate pricing. Call 416-791-1609, open 8am to 8pm, 7 days a week.
Related service: Central AC repair in Richmond Hill