The Most Common Central Air Conditioner Problems

A central air conditioner is essential if you want to be comfortable during the hot summer months, but unfortunately, breakdowns can disrupt your equipment’s ability to cool your home. Luckily, you can troubleshoot some of the most common central air conditioner problems on your own.


To help you stay cool all summer long, we’ve put together a look at the following central air conditioner problems along with troubleshooting tips and when to call in the pros.

  1. No power

  2. Thermostat Issues

  3. Clogged Drain Line

  4. Frozen Cooling Coil

  5. Dirty Outdoor Unit

No Power

If your central AC isn’t cycling on, it may not be getting any power. Here is what you need to do based on the type of HVAC system you have:

  • Gas furnace: Make sure the on-off switch located near your gas furnace is on. Like light switches, they can get easily turn off by children or when you’re changing an air filter.

  • Electric furnace: Electric furnaces have a circuit breaker switch located on or near the furnace. Make sure the switch is in the on position. Note that if the switch has been tripped, it will appear to be on even if it’s not working. Simply, turn the switch off and back on and see if the power returns.

  • All HVAC systems are connected to a circuit breaker, and if you’re not getting power, you should check your breakers. In some cases, a tripped breaker appears to be off, but as indicated above, they can sometimes be in the on position even if they have tripped.

  • Most ACs have an outside disconnect box in addition to the fuse box inside your home. Make sure this switch is on.

Thermostat Issues

If your AC is getting power, make sure your thermostat is set correctly to a temperature below the outside temperature. Check that the switch is turned to cool. It may be off or still set to heat from the winter. Most thermostats also have an auto or on option for the fan — ideally, you should keep this on auto throughout the summer.

Clogged Drain Line

As your AC cools your home, condensation occurs and water droplets exit the system through the condensate line and pool in the drain pan. Occasionally, the line gets clogged, which can cause your AC to stop working.

To remedy this issue, locate your drain line, detach it, and use a wet-dry vacuum to remove the clog. Alternatively, consider having a professional replace the line. Also, remember to empty your drain pan regularly — an overfilling pan can lead to clogs in the line.

Dirty Outdoor Unit

If your AC has power but warm air is coming through the vents, your outdoor AC unit may not be working properly. Here are some of the most common cause of this problem:

  • Failed contractors: Contractors are automatic switches that provide power to the outside compressor, the outside fan, and the furnace’s blower fan. If they break down, they need to be replaced by a professional.

  • Broken capacitor: The capacitor is a rechargeable battery that provides a boost of power to get the AC motor running, and you need a professional to repair this issue.

  • Dirty outdoor condenser coil: Over time, the coil in your outdoor unit can get clogged with dirt and debris. You can clean the coil with a hose if you shut down the AC and turn off the power at the circuit. If your coil is exceptionally clogged, a professional can clean it with special chemicals.

  • Dirty indoor evaporator coil: While you can thaw the coil on your own by running the fan, you need a professional to clean the coil.

  • Refrigerant leak: If your AC is running constantly but the air coming from the vents doesn’t feel that cool, your refrigerant levels are likely to be low, and again, you need a professional to top up the refrigerant. If you have an old AC that uses freon (R-22 refrigerant), you may want to replace your AC rather than paying for a recharge.

Many of the above central AC problems are fairly easy to address on your own, but ideally, you may want to bring in an AC professional and if you have more serious issues, you always need a professional. Remember, central AC systems are very high voltage, and mistakes can shock or electrocute you or damage your equipment. 

At N.E.T.R., Inc, we work hard to keep our customers as comfortable as possible during the hot summers and cold winters in Massachusetts. To ensure you’re getting the most from your central AC, you should schedule an annual maintenance appointment before the cooling season starts. Want to set up service? Need an AC repair? Thinking about investing in a new HVAC system? Then, contact us today. We can help with all your service, repair, and installation needs. 

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