Troubleshooting Ignition System - A.O. Smith 500 User's Information Manual

Fault Messages and Lockout Status (* = stage number: 1 or 2)
Fault Displayed Description
"Display Fail" Communications with UIM interrupted
• Check communication cable to UIM. Try moving to other Internal Communications connector on CCB. Also
check the connectors where the cable is plugged in for best connecting wires.
"Comm. Fail Stg.*" Communications with FCB interrupted
• Same as above. Also try swapping FCB and UIM communications cables.
"Low AC Voltage" Line voltage less than 90 vac
• Check incoming power line for loss of voltage. May also be caused by a power line momentary loss of voltage.
"Low 24VAC" Voltage from transformer less than 18 vac
• Check transformer output. Should be over 24vac. May be caused by excessive current drain or a faulty
transformer
"Brown Out Reset" Indicates a brown out reset occurred
• Caused by a momentary dip in voltage on the CCB +5vdc power bus. Contact factory. (Not considered a
serious problem if it only occurs on very rare occasions.)
"Timeout Reset" Indicates a watchdog reset occurred
• Caused when the micro executes the software in an improper way. Contact factory. (Not considered a
serious problem if it only occurs on very rare occasions.)
"CCB Overflow" Stack overflow - recorded in history only
• Caused when the micro overfills its memory stack. Contact factory. (Not considered a serious problem if it
only occurs on very rare occasions.)
"CCB Underflow" Stack underflow - recorded its history only
• Caused when the micro underfills its memory stack. Contact factory. (Not considered a serious problem if it
only occurs on very rare occasions.)
"Sequence Err" Incorrect flow of critical code
• Caused when the micro executes software code in an incorrect manner. Contact factory.
"A/D Fail CCB" Error in analog input reading
• Caused when the Analog to Digital converter section of the micro operates improperly. Contact factory.
"EEProm Error" Not implemented
"ROM Failure Stg*" ROM contents incorrect
• Caused when the Read Only Memory on one of the FCB micros operates improperly. Contact factory.
"ROM Failure CCB" ROM contents incorrect
• Caused when the Read Only Memory on the CCB micro operates improperly. Contact factory.
"Hdwr Short Stg** FCB output pin shorted
• Caused when a pin on one of the FCB micros is not in the output state it should be in. Contact factory.
"Hdwr Short CCB" CCB output pin shorted
• Caused when a pin on the CCB micro is not in the output state it should be in. Contact factory.
"CPU Fail Stg** FCB processor failed internal check
• Caused when one of the FCB micros does not pass its internal checks. Contact factory.
"CPU Fail CCB" CCB processor failed internal check
• Caused when the CCB micro does not pass its internal checks. Contact factory.
"RAM Failure CCB" CCB Ram check failed
• Caused when the CCB micros Random Access Memory operates incorrectly. Contact factory.
"FCB Comm Timeout" FCB did not receive command from CCB
• Caused when communications between the CCB and the FCB are interrupted. May occur when a surge of
power on a nearby device (i.e. arc welder) creates an EMI burst. Not a serious problem if it occurs rarely.
"No Flow" Water is not flowing
• Caused by the flow switch being open when it should be closed. Check water lines, pump, flow switch
contacts, wiring.
"Blower Prov Stg*" blower pressure is too low
• Caused by either the High-Speed or Low-Speed blower prover switches being open when they should have
been closed. Check blowers, switch contacts, wiring, and for air leaks.

TROUBLESHOOTING IGNITION SYSTEM

17
Red LED Lockout
Continuous Auto Reset
Continuous Auto Reset
Continuous Auto Reset
Continuous Auto Reset
- - - - None
- - - - None
- - - - Immediate Reset
- - - - Immediate Reset
Flashing HARD
Flashing HARD
- - - - None
Flashing HARD
Flashing HARD
Flashing HARD
Flashing HARD
Flashing HARD
Flashing HARD
Flashing HARD
Continuous SOFT
Continuous SOFT
Continuous SOFT