Air Conditioner Faults List and Troubleshooting Complete Guide

Air conditioners are part of everyday life, but problems can still happen and cause a lot of trouble.

What issues are most common, and how can you fix them? This guide explains the answers clearly.

Air Conditioner Troubleshooting Lists

Common Faults	Troubleshooting
Air conditioner is running but not cooling/heating.	1. Check if the thermostat is on "Cool" or "Heat" mode and the temperature setting is lower than the room temperature.
	2. Verify that the air filter is clean and not clogged.
	3. Check if the evaporator and condenser coils are clean and not blocked.
	4. Ensure that the condenser unit's fan is functioning properly.
	5. Check for any refrigerant leaks or low levels.
Air conditioner doesn't cool or heat properly.	1. Check if the thermostat is set to the desired temperature.
	2. Clean or replace the air filter if it's dirty.
	3. Ensure that the condenser unit outside is clean and free from debris.
	4. Verify that the circuit breaker or fuse for the AC unit is not tripped or blown.
	5. Inspect the evaporator and condenser coils for dirt and clean if necessary.
	6. Contact a professional if refrigerant levels are low or if there's a leak.
Air conditioner is not providing sufficient airflow.	1. Clean or replace the air filter to improve air flow and cooling efficiency.
	2. Inspect and clean the evaporator and condenser coils if they're dirty.
	3. Make sure the vents and registers are open and unobstructed.
	4. Check if the blower fan is working correctly.
Air conditioner is constantly turning on and off (short cycling).	1. Adjust the thermostat setting to a temperature closer to the room's actual temperature.
	2. Clean or replace the air filter if it's dirty.
	3. Ensure the evaporator and condenser coils are clean.
	4. Check for any refrigerant leaks.
	5. Verify that the thermostat is properly calibrated.
Air conditioner produces strange or loud noises.	1. Check if the air filter is clean and not obstructed.
	2. Inspect the blower fan for any debris or damage.
	3. Tighten any loose screws or parts in the unit.
	4. Lubricate the motor and moving parts if needed.
	5. If the noise persists, consult a professional.
AC remote control is not working properly.	1. Replace the remote control batteries with fresh ones.
	2. Ensure there are no obstructions between the remote and the AC unit.
	3. Check if the remote's display is functioning and if it's transmitting signals.
	4. If the issue persists, consider getting a new remote or contacting the manufacturer.
AC unit is leaking water.	1. Make sure the condensate drain line is not clogged.
	2. Check if the condensate tray is not overflowing.
	3. Inspect the evaporator coils for ice buildup.
	4. Ensure proper installation and sealing of the unit's components.
	5. Consult a professional if leakage continues.
Uneven cooling or heating in the room.	1. Ensure that all windows and doors are properly closed to prevent drafts.
	2. Verify that the air vents and registers are not blocked by furniture or objects.
	3. Check for obstructions in the ductwork and ensure proper insulation.
	4. Consider using fans to distribute air more evenly throughout the room.
AC unit emits foul odors.	1. Clean or replace the air filter regularly.
	2. Inspect the condensate drain line and pan for mold or algae growth.
	3. Clean the evaporator coils to prevent mold and mildew buildup.
	4. Use an air purifier to help improve indoor air quality.
AC unit is not responding to remote control or control panel.	1. Check if the thermostat is properlyprogrammed and has functional batteries.
	2. Verify if the circuit breaker or fuse for the AC unit is functioning.
	3. Check the power connection to the AC unit.
	4. Reset the AC unit by turning it off and then back on after a few minutes.
	5. If the issue persists, seek professional help.
AC unit trips the circuit breaker or blows fuses.	1. Ensure that the circuit breaker is the correct size for the AC unit.
	2. Check for loose or damaged wiring in the electrical connections.
	3. Clean the air filter and ensure proper airflow to prevent overloading.
	4. Verify if there's a refrigerant leak causing excessive pressure.
AC unit doesn't start at all.	1. Check the thermostat settings and ensure they are correct.
	2. Make sure the remote control or control panel is functioning.
	3. Verify if there's power reaching the AC unit.
	4. Check for blown fuses or tripped circuit breakers.
	5. Inspect the capacitor and contactor for any damage or wear.

Detailed Troubleshooting Sections

Below, we will specifically explain some typical air conditioner faults and solutions.

Insufficient Cooling/Heating

1. Filter is dirty or blocked

Filter with poor air permeability will definitely lose certain cooling capacity. Please clean the filter every 2 weeks to keep the air conditioner good performance.

Troubleshooting:

You can use a high-pressure water gun or rinse directly at the faucet.
After natural drying or high-temperature drying, install the filter again and switch on the A/C.

2. Setting temperature issue

If setting temperature is too low or too high, the compressor needs to work longer to achieve the set temperature, so you will feel the A/C performs badly.

Troubleshooting:

Set the temperature at normal level, like 25-26°C, and after 15-20 minutes, down (in summer) or up (in winter) 2°C, finally get to your comfortable temperature.

This way will minimize the damage to your compressor or A/C main parts (electric board, fan motor), meanwhile can save part of the energy power.

3. Vertical/Horizontal air blade options are wrong

When air conditioner works, electric board has selected the best direction of the air blade according to the working mode, using air convection to achieve the best overall effect.

Troubleshooting:

We recommend referring to the manual according to different modes, choosing a different direction of the air blade, or by the electric board’s self-programmed operation.

4. Incorrect selection of the wind speed for indoor unit

If wind speed is too small, the cooling mode will lead to low air temperature, so that the air outlet in the case of large temperature freezing, while the airflow is small, can’t effectively bring out the cold air in the indoor unit; When heating, the wind speed is small, but the air outlet temperature is high, so room can’t get hot in time.

Troubleshooting:

When you want to cool or heat quickly, adjust the air volume to a larger mode. Don’t set the temperature too low or too high at that time.

When you can obviously feel the room is cold or hot, then according to your own requirements increase or decrease the set temperature.

Air conditioning

5. The compressor has a lower capacity

Some manufacturers use a lower-capacity compressor to claim higher capacity.

For example, they use 12000btu to cheat as 18000btu. So your clients use “18000btu” at the space appropriately for real 18000btu, but the real capacity is 12000btu, the performance is not good indeed.

How to verify?

Troubleshooting:

You can google the series number (see below ↓ ), 9000btu≈2.5kw,12000btu≈3.5kw, 18000btu≈5kw,24000btu≈7kw, etc

(different compressor factory has a different value, but The difference is no more than 5% normally.)

Air conditioner compressor

6. Lack of refrigerant

Compressor needs enough refrigerant to run the whole air conditioner system, if below the average level, the refrigerant can’t effectively meet the cooling or heating needs of the entire system, so can’t achieve the needed effect.

Troubleshooting:

Check the volume of refrigerant every 1-2 years, a professional service company can help you.

Too Noisy 

1. Air conditioning panel is loose

After a long time use, its panel will ease to loose for various reasons, thus, the vibration generated by the air conditioner in constant operation will make the panels rub against each other and cause mechanical noise.

Troubleshooting:

When heard the noisy, close to the panel to listen and watch carefully, you can easily feel the vibration and jitter.

2. Compressor running issue

Compressor installed outside the room, and which is one of the sources of air-conditioning noise. The base of the compressor uses a spring vibration-proof structure. Before delivered, in order to avoid bumps in transportation and compressor rocking damage to the refrigeration system, often tighten the base nut to make the vibration spring compressed to the minimum.

Spring vibration-proof part

Before installing air conditioner, end-user should first pull out the chassis and relax the nut, so that the spring can play a role in avoiding vibration and reducing its vibration and noise during the operation of the compressor.

There are also a small number of compressor internal parts hit the shell, operation, issued intermittent metal percussion sound, encounter this kind of fault, can only open the shell to repair.

Another situation: the compressor bumped the auxiliary copper tube when working. You must keep their space when working, of course, you should find a skilled person or engineer to do that.

The last possibility: compressor has a QUALITY ISSUE. Some factories use un-qualified compressors to cheat.

Some un-qualified compressors are long-time stocked (outlet is blocked),  some other un-qualified compressors are second-hand.

3. Poor installation of internal fan or blade

If the installation is unstable, when the outdoor unit is running, the indoor unit connected with the copper tube is affected by the compressor because of its instability, resulting in resonance.

As a result, noise is generated.

Troubleshooting:

Find a professional installer, or ask your air conditioner supplier for help.

4. The room sound insulation is not good

The walls of the room are made of hollow bricks, and even if the start-up sound of the external unit is normal, it can also be transmitted to the room, then you will feel the sound is loud.

Each customer has different feelings about the sound. Of course, the normal sound of the internal unit is the sound of the air supply, which must be smaller than the fan.

Troubleshooting:

1) Close doors and windows to increase the room airtightness, which can reduce indoor noise.

2) Turn the fan speed to a lower level, or whatever you can tolerate.

Leaks Water

1. Installation leads to air conditioning leakage

Install an air conditioner with an unqualified tilt that will leak due to the accumulation of moisture.

During the installation, the wall hole is too high, resulting in poor drainage of the drainage pipe, so the water plate of the indoor unit is full of water, and the indoor unit will also leak.

Troubleshooting:

No angle tilt when installation, don’t hang up the indoor unit so high (2.5-3m normally)

Water leakage

2. In terms of use, it leads to air conditioning leakage

1) Dirty blocking

Means dust doesn’t clean in time and accumulates in the pipeline, filters, aluminum fins, etc resulting in poor drainage.

2) The drainage pipe is moved or knotted.

3) The drainage pipe (used for a long time) cracked due to plastic aging.

4) If the heat exchanger covered with dust, the heat exchange temperature is uneven, then produce water droplets in the middle of the heat exchanger, which will fall outside the water plate and drop into the room. Or the lack of refrigerant in the air-conditioning system will cause the indoor machine to freeze, and the water droplets formed by ice melting do not drop directly into the water plate but drop to room ground.

Troubleshooting:

Carefully check to find the reasons like the above, then take action accordingly.

Frozen Evaporator Coil / Icing

1. Dirty or blocked air filter
A dirty filter reduces airflow across the evaporator coil. When airflow becomes too weak, the coil temperature drops too low and ice starts to form.

2. Dirty evaporator coil
Dust and dirt on the coil reduce heat exchange and restrict airflow. This can make the coil freeze during cooling operation.

3. Low refrigerant charge
When refrigerant is too low, system pressure drops and the evaporator coil temperature may fall below freezing, which leads to icing.

4. Indoor fan problem
If the indoor fan motor runs weakly, runs at the wrong speed, or stops working properly, the unit cannot move enough air across the coil.

5. Blocked return air or supply air
If furniture, curtains, or other objects block the air inlet or outlet, airflow decreases and the evaporator coil may freeze.

6. Thermostat setting is too low for too long
If you set the temperature too low for a long time, especially in a small room or during mild weather, the system may keep cooling until ice forms on the coil.

7. Continuous operation in unsuitable conditions
If the unit runs for a long time in a low indoor load condition, it may cool the coil too much and cause icing.

8. Drainage or moisture issue
If water does not drain away smoothly, excess moisture around the indoor section may increase the chance of ice buildup.

Troubleshooting:

1. Turn off cooling mode immediately
Stop cooling operation once you see ice on the coil or notice weak airflow. If you keep running the unit, the ice may spread and performance will get worse.

2. Switch to fan-only mode
Run the indoor fan only to help melt the ice faster. Don’t restart cooling until all ice fully melts.

3. Check and clean the air filter
Remove the filter and inspect it carefully. If dust blocks the surface, wash or clean it, let it dry, and install it again.

4. Inspect the air inlet and outlet
Make sure nothing blocks return air or supply air. Keep curtains, boxes, furniture, and other objects away from the unit.

5. Check indoor fan operation
Listen to the fan and feel the airflow. If airflow stays weak after filter cleaning, the fan motor or fan control may have a problem.

6. Clean the evaporator coil if necessary
If the coil surface has heavy dust or dirt, clean it carefully. If dirt buildup is serious, ask a professional technician to handle it.

7. Check for refrigerant shortage
If the unit freezes again after cleaning and airflow correction, low refrigerant may be the reason. In this case, ask a professional service technician to inspect for leakage and recharge the system if needed.

8. Review the temperature setting
Do not set the temperature too low at the beginning. Start with a normal setting and adjust gradually after the room temperature drops.

9. Ask a professional technician for inspection
If icing happens again and again, the problem may involve refrigerant, fan motor, sensor, or control parts. A technician should check the system in detail.

Can’t Switch On

1. The fuse in the special circuit of the air conditioner is blown, or the contact of the power switch is poor.

2. The power supply is so low, then difficult to start the refrigeration compressor in the air conditioner when the voltage is less than 15% of the single-phase normal voltage (220V), that is187V, or less.

3. When the current of the compressor and fan motor is too large, will operate overload protection and cut off the power supply.

4. Whole system has an issue, the main parts ( electric board, motor, compressor) are broken. For this situation, you need to find a skilled service company to make inspections and repairs.

5. Ambient temperature is too high or too low

When the ambient temperature is lower than -10ºC or higher than +45ºC (for T1 compressor) or higher than +55ºC (for T3 compressor), the compressor will stop working, causing the whole air conditioner system failing to work.

Trips the Breaker

1. Too much or too little refrigerant, resulting in compressor protection trip.

2. Air conditioning system is blocked.

3. The outdoor ambient temperature exceeds the normal working range of the air conditioner.

If you use T1 compressor (maximum can stand +45°C) in a very hot area where is more than +45°C, the air conditioner will jump absolutely. You should use T3 compressor (maximum can stand +55°C) in there.

4. The heat exchangers and filters of air conditioners are too dirty, which affects the energy exchange of air conditioners.

5. Power supply voltage exceeds the normal working range of the air conditioner.

6. Outdoor fan motor, fan motor capacitor, indoor and outdoor fan failure.

7. The outdoor temperature sensor is damaged.

Troubleshooting:

Contact Us for help, or your local service company.

Compressor Frequently Switch On/Off

First of all, only non-inverter air conditioner will switch on/off frequently. This is normal because it needs to maintain the temperature accurately at the set temperature.

If the temperature difference between the set temperature and the room temperature is too small, it will aggravate the frequent startup of the non-inverter air conditioner.

In addition, if there are wind-shielding objects around the indoor and outdoor units, it will also affect heat dissipation and cause the air conditioner to switch on/off frequently.

But inverter air conditioner will run at a low speed after reaching the set value to maintain the temperature stable, which can be said to be a “non-stop operation”.

Stop Before Reaching The Set Temperature

The working time of air-conditioning compressor is limited.

Normally, it should stop until it drops to the specified temperature. However, if the ambient temperature is too high or the set temperature of indoor unit is too low, the compressor will take a rest after working for a period of time, even if the temperature doesn’t lower to the set temperature, this is the self-protection of the compressor itself: shutdown and cooling.

If your air-conditioning compressor has short working hours and long intervals,perhaps the compressor is faulty or aging, you should repair or replace it.

FAQs

Q1:How can I quickly tell whether the issue comes from installation, unit sizing, or product quality?

Check the basics first. If the unit worked poorly from day one, wrong sizing or installation often causes the problem.

If the unit worked well at first and then failed later, parts, maintenance, or product quality may play a bigger role.

Q2. When should I repair a unit, and when should I replace the part directly?

Repair the unit when the problem is minor and the part still has stable performance, such as loose wiring, dirt blockage, or drainage issues.

Replace the part directly when it shows clear damage, repeated failure, abnormal noise, overheating, or weak performance after repair.

Q3. Which problems usually do not fall under warranty?

Warranty usually doesn’t cover: incorrect installation, wrong voltage, poor maintenance, blocked filters, damaged drainage pipes, customer misuse, or operation outside the normal working range.

Consumable parts and damage from transport, corrosion, or external force often stay outside of warranty as well.

Q4. What are the common wear parts for air conditioners?

Included: capacitors, fan motors, PCB boards, sensors, contactors, relays, filters, remote controllers, and drainage pipes.

In some models, installers and service teams also keep spare fan blades, louvers, and compressors for after-sales support.

Conclusion