Here is a description of the operation of the Atwood furnace (I am pretty sure you have it and not a Suburban). This comes from Page 30 of the PDF "Atwood Furnace Training Manual". It can be found in the Files section or via this link. https://www.montanaowners.com/forums...?do=file&id=54
You probably are better off downloading the entire PDF. Note: There is a flashing LED inside that indicates the reason for the non-start.
The ON/OFF switch allows power to pass to the circuit breaker
and the thermostat.
The thermostat controls the operating circuit to the furnace by
reacting to room temperature. When room temperature is below
the thermostat set point, the contact closes to allow current to flow
to the relay (relay can be either external or part of the ignition
The circuit breaker limits amperage draw of motor.
The relay allow current to pass to the motor by closing a switch
within the relay. Voltage from the thermostat activates the relay to
turn the fan on. This takes 1-25 seconds (on units with relay on
the ignition control board there is only a 1-2 second delay).
Current flows to the motor to operate the blower. One end of the
motor shaft is for the circulating air wheel and the other side is for
the combustion air wheel.
Circulating air blows against the sail switch and closes the
contacts, completing the circuit. The sail switch is a safety device
that insures air flow before ignition.
The limit switch is a safety device that protects the furnace from
overheating. The contacts in the limit switch open at a given
temperature setting, shutting off power to the electronic ignition
system that controls the gas valve.
As power is applied to the circuit board, the system closes the
1. A timing circuit allows the blower to purge the chamber
2. The board supplies current to the gas valve and causes
it to open.
3. As the valve opens, the board sends a high voltage
spark to the electrode at the burner. The board detects
the presence of a flame. If the flame is not sensed after
approximately six seconds, the board will lock out (after
three tries for ignition, the control will lockout for one
hour unless power is removed or thermostat is
cycled).shutting off power will restart the cycle.
4. If the system does not ignite and the thermostat
remains closed, the blower will remain on until the
thermostat is reset manually on units with an external
relay (units with the relay on the ignition control will
shut the blower off even if the thermostat contacts
remain closed). If the thermostat is has not be satisfied
within one hour the system will try the ignition cycle
When the thermostat senses the desired room air temperature
contact open, removing power from the ignition system and
shutting off the gas valve. The blower runs until the relay opens
(90 seconds) the circuit shutting off current to the motor.
On newer control a diagnostic error code light has been added by
counting the flashes an error code can be determined. See
diagnostic information for code failures.
Number of Flashes Diagnostic Information
1 w/ 3 sec. pause - Air Flow / Limit Fault
2 w/ 3 sec. pause - Flame Sense Fault
3 w/ 3 sec. pause - Ignition Lockout Fault
Steady ON no Flashing - Internal Control Failure