Troubleshooting At The Outdoor Unit Side - Mitsubishi Heavy Industries FDTC40ZHXV Technical Manual

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Troubleshooting at the outdoor unit side

When troubleshooting the outdoor unit, firstly assess the overview of malfunction and try to presume the cause and the faulty
part by checking the error cord dispalyed on the remote controller and flashing pattern of indicator lamps (Red LED and Green
LED), and then proceed further inspection and remedy it.
Self-diagnosis system by microcomputor on indoor and outdoor PCB can assist to find the cause of malfunction smoothly by
making a diagnosis of not only the anomaly of microcomutor, but also the anomaly in power supply system, installation space,
overload resulting from improper charging amount of refrigerant and etc.
Unless the power is reset, the error log is saved in memory and the inspection indicator lamps on outdoor PCB keep flashing
after automatical recovering from malfunction.
After automatical recovering from malfunction, if any another error mode which has a higher priority than the previous error
saved in memory occurs, it is overwritten in memory and is displayed.
[Reset of power supply]
Be sure to avoid electrical shock, when replacing or checking the outdoor control PCB, because some voltage is still retained in
the electrolytic capacitor on the PCB even after shutting down tne power supply to the outdoor unit.
Be sure to start repairing work, after confirming that the Red LED (or Green LED for 71-250type) on the PCB has been
extiguished for more than 10 seconds after more than 3 minutes had been passed since power shut down, and reconfirming that
voltage has been discharged sufficiently by measuring the voltage (DC) between both terminals of electrolytic capacitor (C58)
(Measurment of voltage may be disturbed by the moisture-proof coating. In such case, remove the coating and measure it by
taking care of avoiding electrical shock)
(a) Module of part to be replaced for outdoor unit controller
Outdoor control PCB, Inverter PCB, Temperature thermistor (of outdoor heat exchanger, discharge pipe, ambient air,
power transistor, suction pipe and underneath), Fuses (for power supply and control PCB), Noise filter, Capacitor, Reactor
and Transformer
(b) Replacement procedure of outdoor control PCB
Replace the control PCB according to the following procedure.
1) Model FDC71VN
a) Replace the PCB after elapsing 3 minutes from power OFF.
(Be sure to measure voltage (DC) between T26 and T27 on inverter PCB, and check that the voltage
is discharged sufficiently(10V or less).(Refer to Fig.2))
b) Disconnect the connectors from the control PCB.
c) Match the switches setting (SW4) with the former PCB.
d) Connect the connectors to the control PCB.(Confirm the connectors are not half inserted.)
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