31
Power interruption greater than 80mS may cause the
control to interrupt the operating sequence and resume
as if power was first applied. All power interruptions of any
duration are to be self recovered and not result in a
condition that could cause lockout.
12. Control Internal Diagnostics
a.) Internal microprocessor tests: The software will
perform tests of the internal microprocessor hardware as
much as is practical. A detected failure in internal hardware
will result in lockout with the Status LED blinking rapidly.
b.) Flame sense circuitry diagnostics: The integrity of the
flame sense circuitry is constantly monitored by the
microcontroller. The control will lock out with the status
LED flashing rapidly if a fault is detected in the flame
sense circuitry.
c.) Failed gas valve relay: If the control senses the gas
valve output as energized when it should be de-energized,
and flame is not present, the control shuts off all control
outputs (including the inducer motor) to force the pressure
switch to open. If gas valve remains sensed as energized
15 seconds after the inducer shut off, the inducer is re-
energized to attempt to vent the uncontrollable gas.
If the control senses the gas valve output as energized
when it should be de-energized, and flame is present, the
control keeps the inducer motor and indoor blower motor
energized until flame is removed.
If the control does not sense that the gas valve is energized
when it should be, the control locks out with the Status
LED flashing rapidly.
Combustion Air Blower – All M1M models use a combustion
air blower incorporated in series with the air inlet pipe. Its
purpose is to supply a forced draft method of combustion air.
The quality of air is determined by the inlet orifice ring, located
on the inlet to the motor assembly.
Upon a call for heat under normal conditions, the combustion
blower starts up and supplies combustion air to the chamber.
If motor does not start, check to be sure call for heat is
established and fault light is on solid. See troubleshooting
flow chart and sequence of operation for further details. Then
disconnect blower molex plug and check for voltage at plug.
If voltage is available and motor does not start replace motor.
If power is not available check back through power source and
combustion blower relay contacts. See wiring diagram.
Picture 18. Blower Open Motor
Picture 17. Blower OHM
Picture 15. Combustion Air Blower
Figure 23. Combustion Air Blower
Orifice
Ring
Silicone
Picture 16. Blower Voltage
