Atwood furnace
I have a trailer with a Atwood 7920-II furnace. I have worked it down to the point it gives a code 3 for ignition lockout fault. Does anybody know what that means or what might be causing it? I am gue...
Forum Discussion
Ignition lock out..flame failure
Fan comes on and purges combustion chamber....at same time it is supplying room air flow. That causes sail switch to make up (air flow moves 'paddle' which closes micro switch)....DC Voltage then goes thru sail switch to/thru limit switch and to control board.
When control board gets DC voltage it then sends DC Voltage to 'spark electrode' circuit and to gas valve solenoids.....gas valve opens for 6-8 seconds allowing gas flow to spark electrode.
High voltage spark ignites MAIN FLAME which then generates a miliamp signal (flame ionization/rectification), This miliamp signal goes back to control board to 'PROVE' flame lit. No signal/control board drops DC to gas valve shutting down gas flow and Ignition Lock Out (3 attempts)
You had 'airflow' issues due to low airflow/sail switch not making up......kinda cleaned obstruction so airflow increased/sail switch makes up
Now you have flame failure due to:
*Spark electrode dirty/soot-carbon .....high voltage can cause spark but that miliamp signal can not over come the resistance and go back to control board via spark electrode circuit
*Spark electrode not in direct path of main flame...must be 'engulfed' to generate miliamp signal path
*Ceramic insulator on electrode is cracked---miliamp signal goes to ground
*Spark electrode high voltage wire connection is dirty/corroded/loose...miliamp signal can't flow back to control board
*Main flame lights off but flame is obstructed due to dirty/clogged burner slots
Need to clean up burner area, spark electrode/circuit and combustion-exhaust chamber
http://bryantrv.com/docs2/docs/hflamefurn04.pdf
Fan comes on and purges combustion chamber....at same time it is supplying room air flow. That causes sail switch to make up (air flow moves 'paddle' which closes micro switch)....DC Voltage then goes thru sail switch to/thru limit switch and to control board.
When control board gets DC voltage it then sends DC Voltage to 'spark electrode' circuit and to gas valve solenoids.....gas valve opens for 6-8 seconds allowing gas flow to spark electrode.
High voltage spark ignites MAIN FLAME which then generates a miliamp signal (flame ionization/rectification), This miliamp signal goes back to control board to 'PROVE' flame lit. No signal/control board drops DC to gas valve shutting down gas flow and Ignition Lock Out (3 attempts)
You had 'airflow' issues due to low airflow/sail switch not making up......kinda cleaned obstruction so airflow increased/sail switch makes up
Now you have flame failure due to:
*Spark electrode dirty/soot-carbon .....high voltage can cause spark but that miliamp signal can not over come the resistance and go back to control board via spark electrode circuit
*Spark electrode not in direct path of main flame...must be 'engulfed' to generate miliamp signal path
*Ceramic insulator on electrode is cracked---miliamp signal goes to ground
*Spark electrode high voltage wire connection is dirty/corroded/loose...miliamp signal can't flow back to control board
*Main flame lights off but flame is obstructed due to dirty/clogged burner slots
Need to clean up burner area, spark electrode/circuit and combustion-exhaust chamber
http://bryantrv.com/docs2/docs/hflamefurn04.pdf
