GF - H 4
Indoor Blower Motor
Indoor Serial Port Variable Speed Blower
Motor Test
Step 1
Is the line voltage to the blower motor high volt-
age plug pin #4 and pin #5 correct? (Figure 7)
Furnace blower motor correct voltage is 120 volts AC
and a factory jumper wire must be present connecting
pin #1 and pin #2 together.
Air Handlers blower motor correct voltage is 240 volts
AC and there is no jumper wire connecting pin #1 and
pin #2 together.
Yes: Go to Step 2.
No: Correct line voltage fault.
Figure 7
Step 2
Disconnect the blower motor’s low voltage harness
from the furnace’s IFC or the air handler’s control board
(Figure 8).
Furnace IFC plug is E8.
Air handler’s plug is VS-COMM
Figure 8
Step 3
Jumper 24 volts A/C into pin #3 and #4 in the blower
motor low voltage plug removed from the furnace IFC
or the air handler control board (Figure 9). The blower
motor should run after a short delay. The blower mo-
tor should run at 75% of its programmed torque. Does
the blower motor run?
Yes:
Furnace. Replace the furnace IFC.
Air Handler. Check the Air Handler’s control setup.
If the Air Handler is connected to a communicating
thermostat the Air Handler control must be set up for
a communicating system not a 24 volt AC control
system. If the Air Handler control setup is correct,
replace the Air Handler control board.
No: Go to Step 4.
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