Carrier Air Conditioner Error Codes [Proven Solutions]

Air conditioner error codes are a way to know when there are issues. They usually point you in the right direction if you know what the codes mean. Then, you can fix them. This article explains Carrier air conditioner error codes.

Carrier air conditioner error codes

Carrier Air Conditioner Error Codes – Meaning

The following are the error codes common to Carrier air conditioners and their meaning:

EO – There is an EEPROM parameter error with the indoor unit.

E1 – There is a communication error between the outdoor and indoor units.

E3 – The indoor fan’s speed or the blower speed is not regular. It has gone out of control.

E4 – The indoor unit has a sensor for detecting the room temperature. The error code will appear if it has a T1 open or short circuit.

E5 – The evaporator coil has a temperature sensor for detecting when the coil becomes too cold or too hot. The error code appears if the sensor has a T2 open or short circuit.

EC – The air conditioner may have a leak in the closed system. The code indicates that the refrigerant is leaking from the system.

F1 – The outdoor sensor for detecting the ambient temperature may have a T4 short or open circuit.

F2 – The temperature sensor for the condenser coil may T3 open or short circuit.

F3 – Check the discharge temperature sensor for the compressor. It may have a T5 short or open circuit.

F4 – There is an EEPROM parameter error with the outdoor unit.

F5 – The outdoor fan’s speed or the condenser fan speed is no longer regular. It is out of control.

P0 – There is a malfunction in the strong current protection over IPM.

P1 – This error code represents high or low voltage protection.

P2 – It is a code that shows the compressor’s high-temperature protection

P4 – This code shows a drive error with the inverter compressor.

F8 – if the temperature sensor for the compressor suction becomes defective, this code appears.

L3 – The drive phase current overload may be defective.

L4 – The error code may indicate that the phase current sampling is defective.

F0 – The AC current protection for the outdoor unit may have an issue. It is best to check it. In some models, the error code may also mean the refrigerant level is low or something is blocking the refrigeration system. It may also indicate the pump-down mode.

L1 – Check the drive bus voltage overload protection if you see this code.

L2 – Check the drive bus voltage overflow protection if you see this code.

P5 – Inspect the compressor phase current protection if you see this error code.

P6 – Check the connection between the main control board and the inverter drive. There may be a communication error.

P7 – Inspect the heat sink temperature sensor if this code is displayed. The senor may be malfunctioning.

P8 – Check the IPM over-temperature protection.

P9 – There is a device for preventing freezing in the indoor unit. Check to see its working condition. Also, check the compressor’s contactor; it may be open.

PU – Check the cooling outdoor coil device for preventing overheating.

PE – It may indicate that something is wrong with the heating indoor coil overheat protection.

PC – It points to the cooling outdoor ambient temperature over-low protection.

PH – It points to the heating outdoor ambient temperature over-high protection.

E2 – There is an error with the zero-crossing signal detection.

E7 – The outdoor fan speed is out of control.

E8 – Check the system overload protection.

There are other error codes you may find with the air conditioner, and we will discuss them further down in this article.

Check out these other articles…

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Do Air Conditioners Clean the Air? [Detailed Answer]

Air Conditioner Modes Explained in Detail

Air Conditioner Evaporator [Detailed Guide & Solutions]

Air Conditioner Fan [Detailed Guide, Problems & Solutions]

Air Conditioner Filter [Detailed Guide, Issues & Solutions]

Carrier Air Conditioner Error Code E1 – How to Troubleshoot

Turn the air conditioner off and wait one minute before turning it on again. Use the unit’s remote control to power it. If the unit does not work as it should, inspect the wiring between the outdoor and indoor units. The wires L, N, S, and GND must be correctly connected, and if they are not, correct them. Then, turn the unit off and on again as before.

But if the wire connections are good, go to the outdoor PCB and check the LEDs. If the red and yellow lights are flashing, replace the PCB in the indoor unit and run the air conditioner. But if they are not flashing, it may mean that the PCB in the outdoor unit is not getting enough power supply. Check its wiring and if the connection is correct, you may need to replace the e-box in the outdoor unit. Otherwise, adjust the connection to correct it if it is wrong.

Carrier Air Conditioner Error Code E4 – How to Troubleshoot

Since it is the temperature sensor that may be faulty, you need to check the resistance value. It must correspond with the values in the specification sheet. To do this, find the terminals on the sensor. Different models have varying methods for checking the resistance.

For the RPG20D model, get a multimeter and measure the resistance in each terminal or winding. There are three terminals with different colors: black, white, and red. The resistance value from black to red should be 400 ohms. The value from white to black should be 383 ohms. 

If the sensor shows values within this range, it is in good working condition. The same applies if the values are not exactly accurate, give or take 8%. Values outside these ranges mean the temperature sensor needs a replacement.

For the RPG28D model, the testing steps remain the same, except that the values are different. For this model, the resistance value from black to red should be 260 ohms, give or take 8%. The value from white to black should be 385 ohms, give or take 8%. If the values are outside these ranges, replace the temperature sensor.

Carrier Air Conditioner Error Code E5 – How to Troubleshoot

This error code shows a T2 open or short circuit with the evaporator coil temperature sensor. To troubleshoot and find the source of the problem, go to the PCB and check the sensor connections. If they are wrong, redo the connections, ensuring they are correct this time. But if they are correct, replace the sensor and check the unit again. If the problem continues, replace the PCB for the outdoor unit.

Carrier Air Conditioner Error Code EC – What to Do

This error code usually indicates a refrigerant leak. That means the sealed system has a leak that must be found and fixed as quickly as possible. If this error code appears on your Carrier air conditioner, turn the unit off and disconnect it from electricity. Then, call for professional help.

While waiting for help, ensure there is proper ventilation inside the room, even if there is no odor. The leak may come from either the indoor or outdoor unit, and refrigerant, in large amounts, is dangerous to health. Only a trained professional can detect and repair the leak. In some cases, they may recommend replacing the unit, especially if it is old. When buying a new unit, ensure you get the correct size for your home for adequate cooling and to preserve the life of the unit.

Carrier Air Conditioner Error Code 72 – What to Do

If you find this error code displayed on your Carrier air conditioner, turn off the unit and check the filter. If it is the washable kind, remove and wash it. But if not and it is significantly dirty, replace it. A dirty air filter affects the flow of air across the evaporator coil and reduces the suction pressure. The code indicates low suction pressure. If you clean or replace the filter, turn the thermostat off, wait about five minutes and turn it on again.

If replacing or cleaning the filter does not fix the error code, the problem may stem from low refrigerant. It is a serious issue that needs immediate attention. Contact the Carrier air conditioner manufacturer or an independent HVAC technician for further assistance.

Another possible cause of the error code is the compressor. When there are an internal overload or the capacitor or start relay malfunctions while the air conditioner needs the compressor to run, the error code appears. The compressor may also have internal wiring issues or an open circuit. You will need professional help to test the capacitor and relay if the air conditioner has a relay. Also, the technician will check the compressor’s functionality and recommend a permanent solution.

Carrier Air Conditioner Error Code E3 – How to Troubleshoot

The fan speed in the indoor unit is out of control, causing this error code to appear. Turn off the air conditioner, wait about five seconds, and turn it on again. If the unit does not resume normal operations, turn it off again access the fan, and spin it by hand.

A stiff fan may be a result of worn bearings or a bad motor. You may have to replace the motor if the bearings are out or the motor is bad. But if the bearings and motor are working well and the fan freely spins, check the motor’s wire connections. It will inform you whether or not the motor is getting enough voltage supply. If it is receiving enough power, replace the motor but if not, replace the unit’s control board.

Carrier Air Conditioner Error Code P4 – How to Troubleshoot

The P4 error code in a Carrier air conditioner indicates a problem with the inverter compressor drive. Check the connections to and from the compressor, and see if the wiring sequence is correct. You will need the tech sheet to verify the connections or use the services of an HVAC professional.

If the connections and wiring are wrong, disconnect and reconnect them. Test the air conditioner to see if the problem is fixed but if not, call for service. However, if the connections are correct, you will need a replacement PCB for the outdoor unit. Run the air conditioner again to see if the new control board fixes the problem. If it persists, you may need a new inverter compressor.

Carrier Air Conditioner Error Code P1 – What to Do

The error code usually indicates an over-voltage or too low-voltage protection. To find out what is causing the error code to appear, check the power supply to the unit. Most air conditioners need up to 220 volts to run efficiently. If the power supply is insufficient or unsteady, fix the problem. But if the supply is steady and enough, and the unit is getting power as it should, it may be time to replace the e-box of the outdoor unit.

Carrier Air Conditioner P0 Error Code – How to Troubleshoot

If P0 flashes on the air conditioner or remote display, it indicates an IPM malfunction or shows an IGBT over-strong current protection. To troubleshoot, check to see if the connections between the IPM and outdoor PCB are correct. If the connections are good, check whether or not the IPM is tightly fixed to the radiator.

Tighten the IPM to the radiator if it is loose. Otherwise, replace the IPM if it is tight yet does not function as it should. But if the IPM is good and tight, yet the unit still has trouble functioning, you may have to replace the compressor.

Carrier Air Conditioner Error Code 179 – What It Means

The outdoor unit’s control board may be damaged and in need of a replacement. While it is not a common problem, the board may burn out if there is bad or stormy weather or power surges. This is especially true if the bad weather lasts a long time or there is a lot of lightning, with the air conditioner in use during this time. Consider checking and replacing the board.

But if the board is not the problem, check the connection between the thermostat and the outdoor unit. A lack of communication between the thermostat and the unit causes the error code to appear. Try rewiring the thermostat to get it up and running again as the fault may come from there. Otherwise, consider replacing the thermostat.

Carrier Air Conditioner Fault Code 178 – What It Means

The fault code on a Carrier air conditioner means there is a non-functional PCB or 24-volt control circuit. The problem may stem from the PCB itself or from the thermostat or a bad wire connection. You will need professional help to fix the problem, so contact Carrier or hire an independent HVAC technician.


Error codes do not always mean an appliance is damaged. This rule applies to all types of appliances, including air conditioners and refrigerators. They are usually a way to alert you to faults so that you can quickly fix them. 

This article discusses Carrier air conditioner error codes, their meanings, and how to fix them. Follow the guide and solve minor issues. If the problem persists, contact the manufacturer for professional help. Alternatively, employ the services of an HVAC technician for further assistance.

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