Air Conditioner Not Cooling

10 Reasons Why Your Air Conditioner Is Not Cooling

What more can go wrong? Let's face it, having no A/C or Heat is no joke! Not only do HVAC Technicians charge a hefty diagnostic fee just to diagnose the problem, but some also charge a trip fee, that's right... just for driving out to your home. What if the part you need to get your Air Conditioner back up and running, is half the price quoted by your Tech? Then, that might be a price you're willing to pay.

Here's some helpful advice on diagnosing a very common problem: "Air Conditioner Not Cooling".

Cause# 1

Dirty Air Filter

If your air filter is heavily dirty and clogged, air cannot flow properly through the air conditioner. This greatly reduces the cooling capacity of the air conditioner. Also, if the air filter is clogged, the evaporator coils will frost over. To remove debris from the air filter, try cleaning the filter. If it is not possible to clean the  air filter, then you should replace it.

Cause# 2

Dirty Condenser Coils

The condenser coils dissipate heat as the refrigerant passes through the coils. If the condenser coils are dirty, they won't be able to dissipate the heat as effectively. As debris builds up on the coils, the air conditioner will be come less efficient, which causes the air conditioner to work harder to cool down. If the coils are significantly dirty, the air conditioner will not be able to maintain the proper temperature, and the compressor will run continuously in an attempt to cool the room. Check the condenser coils to determine if they are dirty. If the condenser coils are dirty, clean them. For a more thorough cleaning, you can use an outdoor condenser coil foaming concentrate cleaner or simply hose down the dirty coils. It is recommended you open the top grille of the condensing unit, or unscrew the top part of the cabinet to avoid damaging any electrical parts and/or the fan motor.

Cause# 3

Defective Compressor

The compressor might be defective. However, this isn't usually case. Before replacing the compressor, make sure to check the more commonly defective components, like the overload protector and the compressor capacitor. If the compressor is defective, it should only be replaced by a qualified licensed professional.

Cause# 4

Defective Thermostat

The thermostat monitors the temperature of the air. When the air temperature rises above a set point, the thermostat activates a switch to provide power to the fan and compressor. If the thermostat is defective, the unit will not cool properly. To determine whether or not your tstat is in fact defective, set the air conditioning system to "cooling" and then use a multimeter to test the thermostat for continuity. If your thermostat doesn't have continuity while the air conditioner is set to "cooling", replace the thermostat. Keep in mind, some thermostats may also control a heater, and as a result, it will have 3-terminals. Refer to your A/C's wiring diagram for more info.

Cause# 5

Faulty Thermistor

The thermistor is a sensor connected to the control circuit board that detects the air temperature. The resistance value of the thermistor changes in conjunction with the air temperature. If the air temperature rises, the resistance value will decrease. To determine if the thermistor is faulty, use a multimeter to test for continuity. If the thermistor doesn't have continuity, or if the resistance of the thermistor doesn't change with a change in the temperature, replace the thermistor. For specific temperature and resistance values, check your unit's user manual.

Cause# 6

Defective Control Board

The control circuit board regulates the voltage to the compressor and the fan motor. If the control board fails, some components will not function properly or simply won't work at all. Control circuit boards are often misdiagnosed, so make sure to check more commonly defective parts first before replacing the unit's control board.

Cause# 7

Defective Temperature Control Thermostat

The temperature control thermostat is a sensor that monitors the air temperature and activates a switch to provide power to the fan and compressor when the air temperature drops below a set point. If the thermostat isn't working, the air conditioner will cool continuously or won't cool at all. To determine if the temperature control thermostat is defective, use a multimeter to test for continuity. If it doesn't have continuity, replace it. Keep in mind, some thermostats may also control a heater, and as a result, it will have 3-terminals. Refer to your A/C's wiring diagram for more info.

Cause# 8

Defective Temperature Control Board

If the temperature control board is defective, the fan motor and compressor will not get power. Control boards are often misdiagnosed, so make sure to check other air conditioner parts before replacing the temperature control board. If you are completely certain that all other components are working properly, replace the control board.

Cause# 9

Defective Main Control Board

The main control circuit board regulates the voltage to the compressor and fan motor. If the main board fails, some components will not function properly, or won't work at all. Main control boards are often misdiagnosed, so make sure to check commonly defective parts first, before considering to replace the main control board.

Cause# 10

Burned Out Run Capacitor

The run capacitor is connected to the compressor with electrical leads. If the run capacitor burns out, the compressor will not run. To find out if the capacitor has gone bad, test the capacitor using a multimeter. If the run capacitor has no continuity, replace it.