York CIDH018B21S, Service Manual

Page: 24 / 186

3-2
SM-18001-rev.1
TROUBLESHOOTING
Check the following items if there is any abnormality in the activation of the system.
No. Check Situation Check Method
1 Is any power supply breaker or
fuse open?
Check the voltage (secondary side) of the breaker and also
check the continuity of the fuse with a tester.
2 Is voltage at the secondary side
of the transformer correct?
Disconnect at the secondary side of the transformer and measure
voltage with a tester.
3 Is wiring firmly secured and
correctly connected?
Check that the following wiring connection on O.U./I.U. printed circuit
boards (PCBs) is not loose.
• The connection for thermistors
• The connection for the wired controller cable
• The connection for communication cabling
• Each connection for power supply line
Check that the wiring connection on O.U./I.U. PCBs is not loose or
misconnected on the site according to the “Electrical Wiring Diagram” of
the Engineering Manual.
NOTE:
If the fuse(s) on an I.U. PCB is blown, diagnose the cause of overcurrent and replace the fuse(s).
In addition, check the power supply of optional equipment because the fuse(s) may blow due to an external
power supply failure. Turn off the power for safety.
3.1 Initial Troubleshooting
3.1.1 Checking Electrical Wiring and Power Supply