(5)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 burner controller module (BCM), the flame rod may be dirty, (wash it with soap and water) or defective, or the grounding may be faulty.

Once the 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 #5 on the BCM) in sequence.

The lower valve opens first. Upon full opening, its external switch closes, enabling the second motorized valve to open and full flame to be achieved.

If flame failure occurs within 35-seconds period, the BCM will recycle the ignition sequence once. If flame fails a second time, the system will lock out and the “FLAME FAILURE” pilot will light.

Once main flame is established, the burner will remain in the full fire mode until the drying set point temperature has been reached. At this point, the dryer computer will cycle the top motorized gas valve closed the position. The “OFF” mode will be maintained until the dryer’s temperature falls below the drying set point temperature. The motorized valve will then be returned to the full fire position. The ON/OFF motor of the motorized valve, it moves to the full fire position. “OFF” is achieved when no voltage is applied to the motorized valve.

g.Gas Burner Start-Up

1)New gas lines are filled with air and must be purged before the burner will light. To do this close the upper manual shut-off valve, but leave the pilot line shut-off open. Push in the test and reset button on the cover of the burner controller module (BCM). This will “freeze” the ignition sequence when the pilot flame ignites. This allows time to examine the pilot flame, and measure the flame rod signal to the BCM.

2)Connect a pressure gauge or water tube to the pilot gas pressure tap. Start the dryer. Follow the ignition process by referring to the “Sequence of Operation” section of this manual.

3)When the pilot flame is ignited, the pilot gas pressure should measure 3.5-inches (38.1 mm) water column (W.C.) for natural gas and 1.5-inches (88.9 mm) water column (W.C.) for L.P. (liquid propane) gas. The pilot flame should be about as big as a tennis ball.

4)Once the pilot has been properly set, remove the pressure gauge from the pilot line connect a differential pressure gauge between the main gas pressure tap (HI port) and the air pressure tap (LO port) on the side of the gas burner box. The lines connecting the gauge to these taps must be long enough to allow the gauge to sit outside of the dryer so that the burner section access door can be closed when the dryer runs. Running the dryer with these doors open will give an incorrect air pressure reading.

5)Once this differential gauge is installed, open the main gas shut-off valve and push the test and reset button on the burner controller module (BCM) so that the button springs out. Restart the dryer. The ignition process should now continue to the full gas flow state. The differential gauge should read 2.5-inches (63.5 mm) water column (W.C.) for natural gas and 1.25-inches (31.8 mm) water column (W.C.) for L.P. (liquid propane) gas. If it does not, adjust the top gas valve as described in “Top Motorized Gas Valve” on page 58.

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ADC AD-464 service manual