A.O. Smith 100 Series Service Handbook page 63

CODE
94 Header sensor fault
95 Stack sensor fault
96 Outdoor sensor fault
97 Internal Fault: A2D mismatch
98 Internal Fault: Exceeded VSNSR voltage
99 Internal Fault: Exceeded 28V voltage tolerance
100 Pressure Sensor Fault
101-104 RESERVED
Flame Operation Faults
105 Flame detected out of sequence
106 Flame lost in MFEP
107 Flame lost early in run
108 Flame lost in run
109 Ignition failed
110 Ignition failure occurred
111 Flame current lower than WEAK threshold
112 Pilot test flame timeout
113 Flame circuit timeout
114-116 RESERVED
117 Condensate Fault
118-121 RESERVED
Rate Proving Faults
DESCRIPTION
Servicing should only be performed by a Qualified Service Agent
RECOMMENDED TROUBLESHOOTING OF
LOCKOUT CODES
1. Check wiring and correct any possible errors.
2. Replace the header sensor.
3. If previous steps are correct and fault persists,
replace the module.
1. Check wiring and correct any possible errors.
2. Replace the stack sensor.
3. If previous steps are correct and fault persists,
replace the module.
1. Check wiring and correct any possible errors.
2. Replace the outdoor sensor.
3. If previous steps are correct and fault persists,
replace the module.
Internal Fault.
1. Reset Module.
2. If fault repeats, replace module.
1. Verify the Pressure Sensor is a 4-20ma source.
2. Check wiring and correct any possible errors.
3. Test Pressure Sensor for correct operation.
4. Replace the Pressure sensor.
5. If previous steps are correct and fault persists,
replace the module.
1. Check that flame is not present in the combustion
chamber. Correct any errors.
2. Make sure that the flame detector is wired to the
correct terminal.
3. Make sure the F & G wires are protected from
stray noise pickup.
4. Reset and sequence the module, if code
reappears, replace the flame detector.
5. Reset and sequence the module, if code
reappears, replace the module.
1. Check pilot valve (Main Valve for DSI) wiring and
operation - correct any errors.
2. Check the fuel supply.
3. Check fuel pressure and repeat turndown tests.
4. Check ignition transformer electrode, flame
detector, flame detector siting or flame rod
position.
5. If steps 1 through 4 are correct and the fault
persists, replace the module.
Hold time of recycle and hold option. Will not be a
lockout fault. Hold Only.
Internal hardware test. Not a lockout.
Interrupted Pilot or DSI application and flame lost
when system in "test" mode.
1. Reset the module to restart.
Flame sensed during Initiate or off cycle, hold 240
seconds, if present after 240 seconds, lockout.
1. Check the condensate trap at the back of the
boiler/water heater for any blockage.
2. Check the exhaust vent piping for any blockage.
NOTE
H
H
H
L
L
L
H
H or L
L
L
L
L
H
H
L
L
L
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