Mitsubishi Heavy Industries FDT90VNPWVH Service Manual page 57

(4) Troubleshooting at the outdoor unit
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 code dispalyed on the remote control, and then proceed further inspection and remedy
it.
Self-diagnosis system by microcomputor on indoor unit and outdoor unit PCB can assist to find the cause of malfunction
smoothly by making a diagnosis of not only the anomaly of microcomputer, but also the anomaly in power source
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 unit 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 source]
Be sure to avoid electrical shock, when replacing or checking the outdoor unit PCB, because some voltage is still
retained in the electrolytic capacitor on the PCB even after shutting down the power source to the outdoor unit.
Be sure to start repairing work, 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 control
Outdoor unit PCB, Temperature sensor (of outdoor heat exchanger, discharge pipe, outdoor air), Fuses (for power
source and main PCB)
(b) Replacement procedure of outdoor unit control PCB
Since the following precaution is the important contents for safety, be sure to observe them.
・
WARNING and CAUTION are described as follows:
WARNING
！
CAUTION
！
・ Securely replace the PCB according to this procedure.
If the PCB is incorrectly replaced, it will cause an electric shock or fire.
・ Be sure to check that the power source for the outdoor unit is turned OFF before replacing the
PCB. The PCB replacement under current-carrying will cause an electric shock or fire.
・ After finishing the PCB replacement, check that wiring is correctly connected with the PCB before
power distribution. If the PCB is incorrectly replaced, it will cause an electric shock or fire.
・ Band the wiring so as not to tense because it will cause an electric shock.
Precautions for Safety
Indicates an imminently hazardous situation which will result in death or serious
injury if proper safety procedures and instructions are not adhered to.
Indicates a potentially hazardous situation which may result in minor or moderate
injury if proper safety procedures and instructions are not adhered to.
！
！
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WARNING
CAUTION
'19 • PAC-SM-334