Toshiba HWS-803XWHM3-E Service Manual page 93

[A02] Error Temperature rise and error short circuit
Start
TWI, TWO, and THO
sensor characteristics are
correct
Flow switch is normal
Water outlet
temperature is 70°C
or higher
Hot water from
boiler or other circuits does
not come in
Backup heater is energized
Replace water heat exchange control board
• If Boiler setting is ON (DPSW13-2 is ON) and FC62 is "1", the A02 error is not detected.
(TWI,TWO,THO 70°C)
No
Yes
No
Yes
No
Yes
Yes
No
Yes
(Measure heater current)
No
92
Replace TWI, TWO,
and THO sensors
Replace flow switch
Correct water circuit
(To prevent hot water of
other circuits from entering)
Failure of backup heater
(Too large heater input,
thermostat short circuit)
Replace heater unit