Error Codes Caused by Abnormal Refrigerant Circuit
Error Code 8
This code indicates the temperature of the compressor hot
gas is too high. This error occurs after the PCB has attempted
to correct high temperature by reducing the compressor
speed, adjusting the fan speed, or opening the EEV. Causes
of this type of condition are typically a lack of refrigerant in
the system, excessive heat in the conditioned space, or a
restriction in the refrigeration circuit.
Error Code 16
This error code indicates the system may lack refrigerant.
Recover and check the system charge.
Outdoor Error Code Related to Indoor Unit
Error Code 21
This code indicates the indoor coil has frosted. This condition
can be due to a lack of heat in the conditioned space,
operating the indoor unit at excessively cold air temperature,
a blockage of air flow to the indoor unit, or an issue with the
indoor fan motor. This condition will cause the system to
enter an anti-freezing cycle.
Error Code Related to the PCB
Error Code 1
The EEPROM of the PCB cannot read or write data. Replace
Error Codes Related to the IPM
Error Code 2
The IPM has either failed or has detected excessive current.
Before replacing the IPM, check these potential causes of
• Dirty outdoor coil
• Hot conditioned space
• High temperature or excessive load
• Refrigeration circuit restriction
• Seized compressor
• Faulty wiring or wiring connections
Outdoor Unit Error Codes
This code indicates the IPM is not communicating with the
PCB. Check the wiring and the connections CN9 on the
PCB and CN15 on the IPM. If the connections are good, yet
the boards do not communicate and the code will not clear,
check for correct voltage at the IPM CN15 connection. If the
communication voltage is correct and the high voltage input
is present, replace the IPM. If the communication voltage is
not correct, replace the PCB.
The IPM is protecting the compressor from overload, which
can be caused by low building power supply, restrictions, a
non-condensible in the system, a plugged coil, an excessive
load, or a refrigerant overcharge.
This code indicates the operating voltage of the system
is either too high or too low. Check line voltage for proper
limits. The line voltage supplied to the outdoor unit should
be no lower than 187VAC when the compressor starts.
The running voltage should be no lower than 197VAC. The
incoming line voltage to the outdoor unit should never be
higher than 253VAC. If improper voltage is present, check the
supply voltage circuit from the building for correct wire size
and good connections. If the voltage is still outside operating
limits, contact the power company to have the service
If the line voltage from the power company is correct, check
the output voltage of the Power Filter. This voltage connects
to the IPM at terminals ACL and ACN.
If the voltage is not within specifications shown above,
replace the PFB.
There is a loss of synchronization among the U, V, and W
compressor windings during frequency changes as they slow
down or speed up the compressor.
Possible causes include:
• Unstable power supply
• Internal compressor fault
• IPM fault
• Compressor terminal wiring incorrect
• Poor wiring condition
• Loose compressor wiring connection
TROUBLESHOOTING & REFERENCES
Error Code 4
Error Code 5
Error Code 6
Error Code 18