Common Mini Split Error Codes and How to Fix Them

There are many types of mini splits and brands. Every one of them uses different error codes to indicate faulty and malfunctions. However, some error codes happen to be used by manufacturers repetitively. In this post, I’ll provide some of the most common error codes in mini split and how to fix them.

Note that these error codes may not apply to ALL mini splits. For certain error codes, I provided a list of mini split brands that are likely applicable.

E1 / E6 – Indoor/Outdoor Communication Error

Applicable (but not limited) to: Carrier, Pioneer, Comfort Aire, Perfect Aire, Lennox, MrCool, Senville.

The most common problem with new mini splits is the communication error between the indoor and outdoor units (E1 or E6). There are a few common reasons why this error code shows up:

• The communication or signal wire is not properly connected.
• Either the indoor or outdoor unit PCB is faulty.
• There are electrical frequency disturbances near the signal wire.
• The indoor/outdoor pairing is incorrect.
• The signal wire is faulty (broke in the middle).

To fix this error code, try the following:

• Check if the communication or signal wire is tightly connected and it is connected to the correct terminal.
• Make sure the same signal wire is connected to the same terminal at the indoor and outdoor unit. For example, if the indoor unit L1 terminal uses a red wire, then the outdoor unit L1 terminal must also be connected to the same red wire.
• Make sure the signal wire doesn’t run near TV, radio or other electrical appliances that can distort the signal between the indoor and outdoor unit.
• If you have multiple mini split units, make sure each indoor unit is connected to its assigned outdoor unit.
• For multi-zone systems, make sure the indoor unit signal wire is connected to the correct terminal at the outdoor unit.

When installing multiple mini split units, it is easy and common to mix up the wiring. For example, indoor unit A is supposed to be connected to outdoor unit A but instead connected to outdoor unit B. This may results in the PCB address not match and thus, the E1 error code.

If all the above are tried but you’re still getting the E1 error code, it is likely the indoor or outdoor PCB is faulty. To verify this, swap the PCB or signal wire connection from the suspected faulty one to a good one and see if the error code goes away. If so, you can proceed to replace the PCB.

High Pressure Protection

Some brands such as Gree, Ameristar and Friedrich use E1 to indicate a high pressure trip instead. High pressure is referring to the overpressure of the refrigerant, often due to restrictions such as dirty condenser coil and overcharging of refrigerant.

To fix a high pressure trip, try the following:

• Check if the outdoor unit condenser coil and fan blade are dirty. If so, clean them.
• Check if the outdoor unit fan is running properly and there’s no airflow obstruction.
• Make sure the outdoor unit is well ventilated.
• If possible, check the refrigerant pressure and make sure the low-side pressure (R410A refrigerant) is in the normal range of 110-140 psi. Above 150-160 psi may trigger the error code.

If the outdoor unit can’t dissipate enough heat, high pressure may occur. Anything that can hinder the heat rejection rate such as a slow spinning condenser fan, dirty fan blade and dirty condenser coil can all lead to high pressure and thus, the error code.

If the above are tried but you’re still getting the high pressure error code, it may due to a faulty high pressure switch. Replace the high pressure switch and the error code may go away.

In some cases, your mini split may continue to operate with the E1 error code. It is likely a warning that your mini split is experiencing high pressure but not up to the point where it must cease operation. It is highly recommended you check the above mentioned tasks immediately to avoid a sudden shutdown.

P4 – Inverter Compressor Drive Error

Applicable (but not limited) to: Senville, Ductless Aire, Lennox, Blueridge, Carrier, Midea.

Most mini split brands use P4 error code to indicate faulty related to their inverter compressor. The faulty is likely either the compressor drive error or the compressor discharge temperature is too high.

A few reasons to this error as follows:

• Either the Intelligent Power Module (IPM) or inverter drive, or the PCB is faulty.
• The outdoor unit fan is faulty or the surrounding temperature is too high.
• The compressor is faulty.

P4 is an expensive error code. It often indicates the inverter drive or PCB is broken which needs a new replacement. Meanwhile, the compressor hardly fail unless there are unforeseen circumstances. However, most brands provide 5-7 years of compressor warranty.

This error code is difficult for non-professional to check and identified. Best to call a technician for inspection.

E7 – Indoor/Outdoor Mode Conflict

Applicable but not limited to: Gree, Nortek, AC Pro, Ameristar.

The most common problem associated with the error code E7 is the mode conflict between the indoor and outdoor unit. This error code only happens in multi-zone systems.

E7 error code shows up when you set different indoor units to different modes (cooling or heating). This lead to confusion for the outdoor unit as it can only operate one mode at a time. Set ALL indoor units to either cooling or heating mode only to avoid this error code.

Standard mini split systems can’t cool and heat at the same time. If you need simultaneous cooling and heating, consider a 3-pipe air conditioning system.

E7 error code also happens when you set the mini split to AUTO mode. In AUTO mode, the mini split will automatically switch between cooling mode and heating mode depending on the indoor temperature. The mode change setpoint by default is as follows:

• Cooling mode switch to heating mode at below 68°F indoor temp.
• Heating mode switch to cooling mode at above 77°F indoor temp.

If the mini split is set to AUTO mode and the initial mode is cooling mode, both indoor and outdoor unit will be internally set to cooling mode. If the indoor temperature drops below 68°F, the indoor unit will request to switch to heating mode. However, the outdoor unit will only switch to heating mode when ALL indoor units requested to do so.

Therefore, while the outdoor unit is waiting for the signal from other indoor units, you may notice E7 error code being displayed.

One issue associated with this error is that if one of the indoor units is requesting for a mode change from cooling to heating while other indoor units don’t, the outdoor unit will stay at cooling mode. Thus, you may find the requesting indoor unit not heating the room.

Outdoor Fan Motor Faulty

E7 in certain mini splits indicate the outdoor unit fan motor is faulty. Kindly check if there’s any obstruction to the outdoor fan operation or the fuse is broken. Otherwise, a fan motor replacement is likely needed. Daikin and Mitsubishi mini splits often use E7 to indicate such a faulty.

F0 – Indoor Sensor Faulty or Low Refrigerant

F0 could means the indoor unit temperature sensor or other sensors are faulty. Certain mini splits can detect if there’s a refrigerant gas leak. When it happens, the F0 error code will be displayed.

If non-essential sensors such as an infrared human detecting sensor is faulty, your mini split will still operate but without the ECO mode that relies on the sensor to work.

P0 / H5 – IPM Overcurrent Protection

P0 (or H5 depending on the brand) error code may indicate there is an overcurrent protection triggered in the system. When this happen, try the following:

• Make sure the outdoor fan is clear of any obstruction.
• Check if the outdoor fan and coil is clean.
• Check if the power supply voltage is correct (230V ±10%).
• Check if the power cables are connected securely.
• Inspect the indoor and outdoor PCB for any loose wire.

If the above are tried but the error code still persists, it may due to a faulty overcurrent protecting device. Called up a technician to check. You may need to replace what’s called the IPM module.

P6 – Low Pressure Protection

P6 error code could means the system trip due to the refrigerant pressure too low. This happens when the indoor unit airflow is too low because of dirty filter, coil and blower fan. To fix this error code, try the following:

• Check and clean the filter, coil and blower fan.
• If possible, check the refrigerant pressure. The low-side pressure (R410A refrigerant) should be 110-140 psi. If it drop below 100 psi, low pressure trip may happen.

Insufficient refrigerant in the system can also trigger low pressure protection. In addition, faulty outdoor unit PCB may also lead to random low pressure trip. If the above are tried but the error code still persists, either the outdoor unit PCB or the low pressure switch needs to be replaced.