American Dryer Corp. Phase 7 Gas/Steam AD-464 - Manual (Page 48)

44 American Dryer Corp. 113068 - 7
If ALL safety switches are closed, the burner controller module (BCM) will start the
burner fan motor (BCM terminal #8).
The BCM waits 10-seconds to allow the blower motor to get up to speed, and then checks
that the burner fan combustion air switch (BCM terminal #6) circuit is closed. If this
circuit is open during the drying cycle, the “Air Failure” light emitting diode (L.E.D.) will
light. The gas valve will close, and a “HEATER FAULT” message will be displayed.
In order to prevent this air switch from being jumped out, the BCM checks to ensure that
this circuit is open prior to start-up, then “SYSTEM UNSAFE” L.E.D. will light.
If the airflow switch closes after the burner fan is turned on, the pilot solenoid valve (BCM
terminal #3) is opened for 10-seconds and a spark is produced (BCM terminal #4) by the
burner spark plug, igniting the pilot flame.
The flame rod, which extends into the pilot flame, has 300 VAC on it from the BCM
terminal #S1. The flame lets the current flow from the flame rod to ground, which is then
converted to 3 volts to 11 volts DC by the BCM. The “flame signal” L.E.D. on the BCM
lights up.
The spark plug will turn off 1.5-seconds after the pilot flame is detected. If the pilot flame
should fail during the 10-second period that the pilot solenoid is open, the BCM will reenergize
the spark. If the pilot flame is not established at the end of this 10-second period, the
system will lock out and the “FLAME FAILURE” L.E.D. will light.
The 10-second period when the pilot solenoid opens and a spark is produced is called the
trial-for-ignition (TFI) time. It is selected at either 5-seconds or 10-seconds by a dip
switch located on the back cover of the BCM.
The 3 volt DC to 11 volt DC signal from the flame rod to the BCM can be measured by:
(a) Closing the manual shutoff valve in the main gas line to the burner. Leave the pilot
manual valve open.
(b) Push the Pilot Test/Reset button on the cover of the BCM in to the “test” position.
(c) Start a drying cycle...the BCM will halt the ignition sequence after the pilot is ignited.
The pilot flame should be about the size of a tennis ball and should make the flame
sensor red hot.
(d) Insert the positive probe of a DC voltmeter in to the “flame signal” port on the cover
of the BCM. Connect the negative probe to ground.
(e) If signal is less than 3 volts DC, then the pilot may be too small or too large, there may
be a wiring connection between the flame rod and BCM, the flame rod may be dirty,
(wash it with soap and water) or defective, or the grounding may be faulty.