American Dryer Corp. AD-400 - Manual (Page 46)

If the air flow switch closes after the burner fan is turned on, the pilot solenoid valve (BCM Terminal No.
3) is opened for 10 seconds, and a spark is produced (BCM Terminal No. 4) by the burner spark plug,
igniting the pilot flame.
The flame rod, which extends into the pilot flame, heats up and sends a 3-11 DC voltage signal to the
BCM (Terminal No. SI). The "flame signal" LED on the BCM lights up.
The spark plug will turn off 15 seconds after the pilot flame is detected. If the pilot flame should fail
during the 10-second period that the pilot solenoid is opened, the BCM will re energize 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" LED 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 or 10 seconds by a dip switch located on the back
cover of the BCM.
The 3-11 DC volt signal from the flame rod to the BCM can be measured by:
1. Closing the manual shut-off valve in the main gas line to the burner. Leave the pilot manual
valve open.
2. Push the Test/Reset button on the cover of the burner control module in to the 'Test" position.
3. 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 rod red hot.
4. Insert the positive probe of a DC volt meter into the "flame signal" port on the cover
of the BCM. Connect the negative probe to ground.
5. If the signal is less than 3 VDC, then the pilot may be too small or too large, there may be a
faulty wiring connection between the flame rod and burner controller module, the flame rod
may be dirty, (wash it with soap and water) or defective, or the grounding may be faulty.
Once the 3-11 VDC flame probe signal is detected by the BCM, it waits 5 seconds to allow the pilot to
stabilize and then opens the main motorized gas valves (Terminal No. 5 on the BCM) in sequence.
The lower valve opens first. Upon fully opening, its internal switch closes, enabling the second
motorized valve to open. When the second motorized gas valve is fully open an internal limit switch is
closed causing the Hi-Lo Signal from the dryer's computer to be applied.
If a flame failure occurs within 35 seconds of the beginning of this sequence, the system will lock out and
the "Flame Failure" LED will light.
If the flame should fail after this 35-second period, the burner controller module will recycle the ignition
sequence once. If the flame fails a second time, the system will lock out and the "Flame Failure" pilot will
light.
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