A.O. Smith T-H2-DV Service Manual page 47

Error Code
4 Check for soot on the flame rod
[1] Clean the flame rod
121
[2] PCB fault
During operation: more than 1 μA through the flame rod wire (orange)
5 Disconnected/damaged O.H.C.F.
V isual inspection: connection/breakage of wires.
Error code is
Normal: 1 Ωor less between blue & blue
shown after
6 Check if hi-limit switch is properly functioning.
three failed
7 Disconnected/damaged hi-limit switch. (Refer to section 10-14)
attempts at
V isual inspection: connection/breakage of wires.
ignition
Normal: 1 Ωor less between blue & blue
Error Code
Disconnected/short-circuited output thermistor
311
1 Output thermistor fault
V isual inspection: connection/breakage of wires and/or debris on
thermistor.
Check voltage/resistance between black & black (#12).
Refer to Section 8 (A)for proper range of values.
Error Code
Disconnected/short-circuited inlet thermistor
321
1 Inlet thermistor fault
V isual inspection: connection/breakage of wires and/or debris on
thermistor.
Check voltage/resistance between black & black (#42).
Refer to Section 8 (A) for proper range of values.
Error Code
Disconnected/short-circuited mixing thermistor
331
1 Mixing thermistor fault
V isual inspection: connection/breakage of wires and/or debris on
thermistor.
Check voltage/resistance between black & black (#113).
Refer to Section 8 (A) for proper range of values.
Diagnosis
Malfunction description
Diagnosis
Malfunction description
Diagnosis
Malfunction description
Diagnosis
47
T-H2-DV/T-H2-OS Service Manual
(Refer to section 10-16)
Cancellation method
Turn off the power or water supply
(Refer to section 10-12)
Cancellation method
Turn off the power or water supply
(Refer to section 10-12)
Cancellation method
Turn off the power or water supply
(Refer to section 10-12)
CONFIDENTIAL
Ver. 1.01
Checkpoint
I
C2
C1
Checkpoint
E2
Checkpoint
E3
Checkpoint
E1