Wiring Diagrams; Troubleshooting - Carrier 120/C Series Installation, Start-Up, Operating And Service And Maintenance Instructions

blower motor BLWM will remain on for the selected blower-
OFF delay period then switch to continuous-blower speed.
When the R-to-W-and-Y/Y2, R-to-W-and-Y/Y2-and-G, R-to-
W-and-Y1-and-Y/Y2, or R-to-W-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 HEAT speed, and
begin a heating 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 HEAT speed. When the W 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-and-Y/Y2-and-G or
R-to-W-and-Y1-and-Y/Y2-and-G signals disappear at the
same time, the blower motor BLWM will remain on for the
selected blower-OFF delay period. If the R-to-W-and-Y/Y2 or
R-to-W-and-Y1-and-Y/Y2 signals disappear, leaving the G
signal, the blower motor BLWM will remain on for the
selected blower-OFF delay period then switch to continuous-
blower speed.
Step 4—Wiring Diagrams
Refer to Fig. 56 for wiring diagram.
Step 5—Troubleshooting
Refer to the service label. (See Fig. 55—Service Label.)
The Troubleshooting Guide can be a useful tool in isolating
furnace operation problems. Beginning with the word "Start,"
answer each question and follow the appropriate arrow to the next
item.
The Guide will help to identify the problem or failed component.
After replacing any component, verify correct operation sequence.
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