Mitsubishi Electric City Multi PQHY-P72 Service Handbook page 234

Error definition and error
Error Code
2503 Drain sensor When a short or an open
failure is detected during opera-
tion (cannot be detected
during OFF).
Short :
detectable at 90°C
[194°F] or higher
Open :
detectable at
-20°C [-4°F] or lower
2600 Water leakage
2601 Water supply
cut-off
4103 Reverse 1. When turning on the
phase/open power, the operation
phase cannot be started be-
cause of the open
phase of one of the
power lines (L1, L2 or
L3).
2. The operation cannot
be started because of
the reserve phase of
one of the power lines
(L1, L2 or L3).
detection method
(1) Thermistor failure
(2) Connector contact failure
(loose connector)
(3) Disconnected wire or par-
tial disconnected ther-
mistor wire
Indoor board (detection circuit)
failure
- Water leaks from the pipes in
such as the humidifier.
- (1) The water tank of the hu-
midifier is empty.
(2) The solenoid valve for hu-
midification is OFF.
(3) Disconnected float switch
(4) Poor operation of float
switch
(5) Frozen water tank
(1) Faulty wiring
(2) Main board failure
(1) Power supply error
Open phase of power
supply voltage
Power-supply voltage
drop
(2) Faulty wiring
Between the power supply
terminal block (TB1) and
the main boards (CN20
and 21)
(3) A fuse is blown.
(4) Main board failure
- 225 -
Cause Check method and remedy
Check the thermistor resistance.
0°C [32°F] : 6.0 kohm
10°C [50°F] : 3.9 kohm
20°C [68°F] : 2.6 kohm
30°C [86°F] : 1.8 kohm
40°C [104°F] : 1.3 kohm
Check the connector contact.
If no fault is found, the indoor board
is a failure.
Check the location of the leak.
Check the amount of supply water.
Check for the solenoid valve and for
the connection.
Check the connector.
Check the connecting part.
Check for the float switch.
Turn off the power source of the wa-
ter tank to defrost, and turn it on
again.
Check whether the phase of the
power supply terminal block (TB1)
is normal.
Check the wiring between the pow-
er supply terminal block (TB1) and
the main boards (CN20 and
CN21).
TB1
If the above faults are not found, the
main board is faulty.
Check the input resistance of the
power supply terminal block (TB1).
Measure voltages of pin 5 of the
male connector (CN20) on the
main board and between pins 1
and 3 of the male connector
(CN21) on the main board.
If the voltage is not the same as the
power supply voltage, the wiring is
faulty.
Check whether the fuses of the main
board (both F01 and F02) are not
blown.
If the above faults are not found, the
main board is faulty.
[ IX Troubleshooting ]
Pin
L1 CN20 5Pin
L2 CN21 3Pin
L3 CN21 1Pin