Panasonic U-72MF2U9 Service Manual page 181

3. 3WAY Alarm Codes
H21, H31 Alarm
Alarm code H21, H31
Alarm meaning H21 : HIC for 2nd compressor has failure. Overcurrent or overheat of HIC.
H31 : HIC for 1st compressor has failure. Overcurrent or overheat of HIC.
Alarm conditions This alarm occurs when the microcomputer identifies a trouble signal (indicating abnormal HIC
temperature or other trouble) from the HIC.
The HIC judges the current and temperature, and outputs the trouble signal. In general this
indicates trouble with the HIC itself.
Probable cause Overcurrent in HIC circuit, and the resultant abnormal heating, caused by HIC failure
Check Check the power wiring and connector wiring. If the wiring and connectors are normal, use a
tester to measure the resistance between the compressor HIC power (DC+) and ground (DC–).
If there is a short-circuit, there is an HIC malfunction.
HIC PCB for Type 72,120 and 144
(A747843)
HIC PCB for Type 96
(A747846)
Correction If an HIC failure is found, replace the PCB.
Example —
Notes Turn OFF the power, and check the continuity of DC+ and DC– on the HIC PCB.
L04 Alarm
Alarm code L04
Alarm meaning Duplicate system address setting on outdoor units.
Alarm conditions Communication by inter-unit control wiring was received that contained the same address as
that unit 5 times or more within 3 minutes.
Probable cause Incorrect outdoor system address settings
Check Check the system address settings again.
Correction Correct the system address settings.
Example —
Notes Recovery from this alarm occurs automatically (when communication that contains the same
address as that unit is not received for 3 minutes after detection).
DC+
(P)
DC+
(P)
5 - 19
3WAY VRF SYSTEM
Trouble Diagnosis
DC-
(N)
DC-
(N)
1
2
3
4
5
6
7
8
9