Here we cover eleven common problems you may experience with your air conditioner, with suggestions on how to fix them.
However, note that it’s vital to call a suitably qualified technician rather than ever attempting to open up a unit or work with internal parts, which could put you at risk of electric shock and invalidate the warranty on your air conditioning system.
The air conditioner isn’t cooling even though it’s running
This is the most common problem and has several possible causes. Here’s what you can do:
check for a dirty air filter or a blocked condensate drain – clean or change the filter and empty the drain, if necessary
ensure there’s enough refrigerant in the system and check that there aren’t any leaks before adding more coolant
turn off the power for a period in case the air conditioner’s coil has frozen; this may result from dirty filters, a lack of coolant, or a malfunction in the blower fan
if you have a central air conditioning unit and some rooms are warmer than others, call a technician and ask about having dampers placed in the system.
The air conditioner won’t switch on
This could mean a problem with the thermostat or a faulty power supply.
First, check the thermostat. Make sure it’s set to “cool” mode and then decrease the temperature. If this doesn’t work, check for a tripped breaker or blown fuse and reset the electricity to see if that solves the problem. Also, check the wires to see if this is affecting the power supply.
If this doesn’t solve the problem, call a technician to check whether the cooling system’s motor is broken and whether its wiring is still intact.
There is no airflow from the registers
How you treat this problem depends largely on the type of air conditioner you have in your home or office.
First, check whether the circuit breaker/trip switch has tripped. If so, give it a few minutes and then reset it.
If this doesn’t work, it may mean that the blower belt needs to be replaced. This is a relatively simple procedure but would need to be performed by a professional.
If neither of these two things works, the condensate pump reservoir may need emptying or the thermostat, control board or wiring may be faulty.
Your air conditioner is blowing hot air
There could be several causes for this. To test for and address each of these, you can do the following:
recalibrate or replace the thermostat in case it’s responsible for the problem (digital thermostats tend to be a better option in this situation)
dirty filters interrupt airflow, so check and, if necessary, replace the unit’s air filter; the position of the filter will depend on the type of air conditioner
make sure you switch the air conditioner off and then gently brush out any debris in case its evaporator or condenser is clogged
with the power disconnected, manually clean the more accessible condenser fins and coils by gently spraying with clean water; however, note that annual professional maintenance is vital for ensuring coils don’t get damaged
check the refrigerant – you may need to top it up.
The fan isn’t working
If the fan isn’t running, an air conditioner will not cool properly. There are several things you can try to fix this:
check if anything is preventing the unit from receiving power, like tripped switches or wiring issues
try to reset the air conditioner by switching the reset button
after you’ve switched off the unit and unplugged it (if applicable), try to spin the fan blades clockwise and remove anything that’s blocking the fan
if the unit’s filter is dirty, clean it or replace it if necessary.
If all these fixes don’t solve the problem, there may be an issue with the control panel, internal control board, or some other internal part. Most often it’s the capacitor – a small cylindrical object that sends jolts to start the motor – that needs replacing, especially if the system is humming and the fans aren’t turning.
The control panel is faulty
This is most likely an issue with the thermostat or an internal part. Try these troubleshooting steps:
make sure the thermostat is set to “cool” mode and check for any noticeable difference after lowering the temperature by five degrees
try replacing the batteries
reset the thermostat to manufacturer defaults, following the manufacturer’s instructions
if the air conditioner is a central unit, check for any loose wires or screws and tighten and secure where necessary
if the air conditioning is a window unit, unplug it and try resetting it.
Central units can be complex. Window units are tricky too because users don’t have access to the interiors of the units. Usually, it’s best to have any significant repairs done by a professional. In some instances, it may be less expensive to replace a window unit than to have it fixed.
Having your air conditioner serviced regularly can help prevent serious problems from occurring and significantly extend a unit’s lifespan.
The air conditioner is leaking or it’s not reducing humidity
Air conditioning units create condensation, which needs to be drained properly to avoid leaks or extra moisture in the air.
Clogged drain channels or a broken condensate pump prevent a unit from reducing humidity. The resulting excess moisture may cause discoloration on walls and carpets.
Here’s what you can do:
disconnect the power and unclog the drain channels by passing a stiff wire through them
with the power disconnected, clean the pump system of algae with an appropriate bleach solution
check for leaking pumps that may need replacing
ensure electrical connections to the pump are functional – a condenser that won’t run may not be receiving the cooling control signal from the thermostat.
Also check safety switches, the oil level, and refrigerant pressure. If the refrigerant is leaking, the low-pressure safety may have been switched.
The air conditioner never turns off
An air conditioner should turn off occasionally – no matter how hot it is outside. This could mean several things, but most likely indicates a problem with the fan. Make sure the fan is running at the optimal speed by cleaning the blades – a layer of grime on the fan blades can slow it down, reducing its efficiency.
The condenser and filters could also be filthy. A good clean using professional products should be able to resolve this problem.
Other issues that you may need to look out for include a faulty thermostat or a low refrigerant charge. Also, check to see if the evaporator coil is frozen. This can happen if the unit has been blowing warm air from the supply vents while running constantly. If so, switch off the unit and contact a technician.
A unit that turns on and off constantly is most likely one with a dirty or blocked condenser or evaporator. With the power disconnected, give the entire unit a clean to clear any debris or obstructions.
The unit is making strange noises
It’s normal for an air conditioner to make some noise, but noises you don’t recognise could indicate a problem.
Often the type of noise you’re hearing is an important clue to the nature of the problem:
squealing sounds indicate belt problems and can be fixed by properly aligning the belt or replacing it
a grinding noise typically indicates a problem with the motor’s bearings; make sure a technician oils the air conditioner motor at the beginning of each summer
rattling or harsh humming noises may indicate loose, dirty, or bent fan blades or coil fins; try bending blades gently back in place, use a vacuum cleaner with a brush attachment to clean and ensure screws are properly tightened
pinging or popping may be due to a loose flap of metal in the ductwork
a rattling noise may indicate that you need to tighten cover panels.
The air conditioner sets off the trip switch
An air conditioner won’t work if it constantly trips the circuit breaker when it comes on.
One step you can take to troubleshoot the problem yourself is to ensure the air filter is clean. A filthy filter forces the fan to work harder, which uses more electricity and can trip the breaker.
For the rest, you’ll need to call a qualified technician. It’s likely the technician will take troubleshooting steps like these:
check the breaker and see if it needs replacing
check if the motor has shorted and replaced it if necessary
check if the compressor could be grounded, meaning the electrical wiring inside the compressor has broken and hit the side of the compressor
if the compressor has trouble starting, check for a burned wire and determine whether the compressor or start capacitor is defective.
There’s an unusual odour coming from the air conditioner
There are several possible causes for unusual odours, including dirty filters and filthy ducts.
Ensure regular professional cleans of the air conditioning unit, including the filters and ducts, and make sure that water is drained properly. The technician should also check for mildew and fungus.
Electrical odours can result from overheating parts and need to be checked by a technician.