Is your air conditioner blowing but not cooling? Here’s a quick rundown of the issue. Troubleshooting air conditioning isn’t difficult. It proceeds along a set pattern with the easiest things tested first and more difficult later.
These are very simple things that unfortunately can account for unnecessary and expensive service calls. They fall under the, “Duh!” category, but have to be mentioned.
- Unit is set on “fan only.” Modern window and central air systems have a setting for air flow only; the cooling function is shut off. This is used to provide air circulation or fresh air.
- Temperature is set too high. Central air systems may have a setting for the fan – auto or manual. When the temperature in the house is lower than the cut-off for the cooling cycle, and the fan is set on manual (or always on) it will continue to blow, even though the thermostat hasn’t engaged the cooling coils.
- Filter is clogged – always a good idea to check and replace if needed. Reduced air flow can make the inside coils ice over1.
- Outside condenser coils are clogged with debris. When the AC is running, you should feel warm (or hot) air being blown away from the exhaust of the unit. You can clean leaves away and improve air flow.
- Water has built up under the cooling coils on the indoor unit – some systems collect water and have an automatic shut off for the cooling coils when the sensor is tripped. Remove the water (shop vac) and check for clog in any drain tube2.
- AC is shut off or central air is in heating mode. This sometimes happens when outside temperatures are fluctuating and different household members are changing the settings from heat to cool without telling others.
- Miswired thermostat or low battery in thermostat. Since many modern thermostats control heating, cooling and the fan, a problem here can lead to very odd symptoms. A tech may hardwire to jump the thermostat, but homeowners can make sure it’s firmly set in place and has a good battery.
- Blown fuse in household fuse box – for central air, the outside unit and the inside fan blower will run off of different fuses. Check the house fuses to see if one is tripped – if it trips or blows after resetting, stop and call a professional.
- Outside fuse blown – there is usually a separate outside junction box and circuit breaker for central AC systems. If you reset this and it trips again, stop and call a professional.
CALL A PRO:
- If the cooling tubes (coils or feed lines) are not cold, and the compressor is running, you may be low on Freon (or other coolant). Since systems are sealed, this would indicate a leak somewhere. You will need to have a tech add Freon and track down the leak3.
- For split systems, a crimped coolant line can prevent flow to the indoor unit. This usually happened after some interior construction – the line will have to be repaired4.
- If the compressor is not running at all, there can be several problems, ranging from a blown capacitor to a seized motor. This will require professional diagnosis and repair.
- Outside exhaust fan isn’t running. Unless this is a fuse problem, you will have to call a pro to trouble shoot the fan motor or the circuitry.
What not to do:
Modern air conditioners are technically advanced and not designed for do-it-yourselfers. Window and small units are sealed with almost no user-replaceable items (except for the filter). Larger equipment is also complex, and added to that is the expense that comes with a goof. If you try to repair something you aren’t qualified to deal with, not only will it cost more to fix, but your warranty might be voided as well.
Be extremely careful around electricity! Air conditioners draw a great deal of power; capacitors bump this up even higher. Make sure all power is off before you think about opening the case. Better yet, leave anything inside to the pros.