Fault code C5, CH5 or 5 flashes
This fault code indicates a communication error between the indoor and outdoor units.
If there is a communication error fault CH05, will appear within 5 minutes of powering
up the system.
Communications between the outdoor and indoor units are via terminal 3 and N of
the interconnecting cable. Communications errors can be due to:
1. Cable and cable connection faults.
2. Devices such as an external pump connected to the communications
terminals
3. Faulty indoor or outdoor PCBs.
If there is a communications error CH05, then first check the terminals at both the
indoor and outdoor units for any devices other than the interconnecting cable.
Remove such equipment, and connect them elsewhere. If the fault persists, proceed
as follows:
1. Disconnect the signal cable at both ends (Terminal 3).
2. With the INDOOR unit powered up and switched on, check the DC voltage at
the INDOOR unit between the signal (terminal 3) and neutral. Connect the red
lead from your meter to 3 and the Black lead to N, the Voltage should be
negative, and fluctuating up to about -70 V. If there is no voltage, the indoor
PCB is faulty
3. With the OUTDOOR unit powered up and switched on, check the DC voltage
at the OUTDOOR unit between the signal (terminal 3) and neutral, connect
the red lead from your meter to 3 and the black lead to N, It should be positive,
fluctuating up to about +70 V. If there is no voltage, the outdoor PCB is faulty
4. If the tests in 2 and 3 above show the correct voltage, the fault lies in the
interconnecting cable. Remove all cores at both ends, and check for open
and short circuits, including shorts to earth. Check also that there are no
switches on the signal wire, since poor contact can cause the problem. Check
also that there are adequate earth connections at both the indoor and outdoor
units.
5. When communications are healthy, there should be up to +70V DC between
the signal and neutral wires when the unit is running and the interconnecting
cable is connected.

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