SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MXT
Specifications subject to change without notice.
440 04 4321 04 27
(same speed as LO HEAT), and begin a low−heat cycle.
The blower motor BLWM will remain on until the end of
the prepurge period, then shut off for 24 seconds then
come back on at LO HEAT speed. When the W/W1 input
signal disappears, the furnace control begins a normal
inducer post−purge period and the blower remains
running at LO HEAT speed. If the R−to−
W/W1−and−Y1−and−G signals disappear at the same
time, the blower motor BLWM will remain on for the
selected heat−off delay period. If the
R−to−W/W1−and−Y1 signals disappear, leaving the G
signal, the blower motor BLWM will remain on for the
selected heat−off delay period then switch to
continuous−blower speed.
When the R−to−W/W1−and−Y/Y2, R−to−W/W1−and−
Y/Y2− and−G, R−to−W/W1−and−Y1−and−Y/Y2, or
R−to−W/W1−and− Y1−and−Y/Y2−and−G circuits are
energized the furnace control CPU will switch to or turn
on the blower motor BLWM at COOL speed, and begin a
high−heat cycle. The blower motor BLWM will remain on
until the end of the prepurge period, then shut off for 24
seconds then come back on at HI HEAT speed. When
the W/W1 input signal disappears, the furnace control
begins a normal inducer post−purge period and the
blower switches to COOL speed after a 3 second delay.
If the R−to−W/W1
−and−Y/Y2−and−G or
R−to−W/W1−and−Y1−and− Y/Y2−and−G signals
disappear at the same time, the blower motor BLWM will
remain on for the selected heat−off delay period. If the
R−to−W/W1−and−Y/Y2 or R−to−W/W1−
and−Y1−and−Y/Y2 signals disappear, leaving the G
signal, the blower motor BLWM will remain on for the
selected heat−off delay period then switch to
continuous−blower speed.
Component Self Test
Refer to page 14 for instructions.
Figure 17
Two−Stage Furnace with Single−Speed
Air Conditioner
NOTE 9
Figure 18
Two−Stage Furnace with Two−Stage Air
Conditioner
NOTE 9
Figure 19
Two−Stage Furnace with Single−Stage
Heat Pump (Dual Fuel)
NOTE 9
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