Is Your Air Conditioner Not Working?

Your air conditioner has decided stop cooling on the hottest day of the year. Before you call in an ac service technician, there are a few things that you should check yourself, using our HVAC troubleshooting guide below.

After going through the complete checklist, if your air conditioner is still not keeping you cool, call your hvac service contractor. Have this list handy when you call, as it will help your service contractor’s dispatcher in setting up a service call. If you do not have a regular air conditioning service contractor, call us for prompt, courteous service at 817-691-6014.

Thermostat Check

  • Is the temperature set at least 3 degrees below current room temperature?
  • If your thermostat is electronic, are the batteries charged?

If your thermostat has a switch to control the furnace fan, switch the fan “ON”. (This switch will usually be located at the bottom of the thermostat, closer to the left side and will be marked “ON” and “AUTO”.) Listen to hear the furnace fan coming on. If you cannot hear the fan, go to one of the supply registers (air outlets) and see if you can feel any air coming out. If the fan is not running, there may be no power to the furnace. If the fan is running, proceed to the electrical check step below. If the thermostat is set properly, the next step is to check to see that there is power to both the furnace and air conditioning unit.

Note: Some electronic thermostats have a delay built in to protect the air conditioner from being accidentally switched on while the furnace is running. This delay can be up to 15 minutes.

Digital HVAC Thermostat

Electrical Check

Locate the emergency shut-off switch for the furnace and make sure it is turned on. In most homes the emergency shut-off switch look just like a regular light switch and will be located close to the furnace. It is quite common for this switch to be turned off accidentally. If the switch is ON, but the fan still doesn’t operate, proceed to the electrical panel check.

Electrical Panel (Furnace and Air Conditioner)
Here, you are going to make sure that the main power is on to both the furnace and air conditioner. Locate the breaker or fuses in your home’s main electrical panel for the furnace and air conditioning unit. Make sure the breakers are not tripped or the fuses are not tripped. If a breaker has been tripped it will be in a position that is between ON and OFF. Reset the breaker (turn all the way OFF, then back ON).

If your home has fuses, check to see if the fuse for the furnace is blown. If so, replace it with the SAME SIZE fuse. Do not increase the size of the fuse.

WARNING: If a breaker keeps tripping or a fuse keeps blowing, you should contact a qualified service technician to inspect your system to determine the problem.

Air Conditioner
Some central air units are installed with a switch, or electrical disconnect, mounted outside to turn off the main power to the unit. Whether or not you have a switch will depend on the electrical code in your area. If you have a disconnect switch check to make sure it is in the “ON” position. The disconnect switch maybe fused, check their status. Is the fan running on the unit outside? If the fan is running you have power to the unit. Some air conditioners will make a little buzzing sound, even when they are not running, have you ever noticed it before? Can you hear it now?

Electrical Check Summary:
If you have determined that there is power to both the furnace and air conditioner, and you are still not getting any cool air, continue with the checklist. If you have discovered that the furnace or air conditioner is not getting any power, call your hvac service contractor or call us for prompt service.

Air Flow Check

Dirty AC Vents

If your unit seems to be operating, just not producing any cool air, you may have an airflow restriction. Air conditioning units require a lot of air to operate, if anything has interrupted the airflow, the unit may still work, but at a much reduced capacity.

Check the following:

  • Make sure the furnace filter is clean.
  • Make sure the return air grills are not blocked or plugged with dirt.
  • Open all supply air grills.
  • Check to see if there is anything blocking airflow around the outside unit.

Check AC Unit for Ice

Icy AC Unit

Is there ice building up on the pipes coming out of your furnace, into your air conditioner?
Touch the plenum (sheet metal box that comes off of the furnace, the evaporator coil is installed inside), does it feel very cold? If it does, it could be an indication that the evaporator coil is frozen. Ice forming on the pipes or the coil inside the furnace will usually be caused by a restriction in the air flow across the evaporator coil or your unit is low on refrigerant. If the problem is an air flow restriction, you can probably correct the problem yourself, if it is the refrigerant, you will have to call in a service technician.

Restricted or reduced air flow can be caused by one, or a combination of the following:

  • Furnace air filter is very dirty and needs to be cleaned or changed.
  • Your evaporator coil is plugged with dirt and needs to be cleaned.
  • Your condenser coil (outside unit) is plugged and needs to be cleaned.
  • Your furnace fan, or blower coil, motor is not moving enough air. The motor may be burnt out, a pulley may be broken or a fan belt may be broken.

If your unit is low on refrigerant, it is because there is a leak in the system. The leak must be repaired BEFORE new refrigerant can be added. Leaks can be very tricky to find and may require several visits by a service technician.

For help with any issues you experience with your Air Conditioning call Denco.