75
DIAGNOSING BLOWER MOTOR ISSUES
1. MOTOR POWER AND COMMUNICATIONS IS-
SUES (FAULT CODE “68”)
Is the motor communicating properly with the furnace
control? If not, the fault code “68” will be displayed
any time there is a call for cooling, heating or contin-
uous fan. To determine the cause of this issue, fol-
low these steps:
A. Remove the line voltage connector from the
motor. This is the 5-pin connector. With the door
switch closed, verify that there is 115-120VAC be-
tween pins 4 and 5 of the connector (see photos
in Figure 45B). If no line voltage is detected,
check the wiring and correct the issue. Line volt-
age should be present at these pins any time the
furnace is powered. Make sure that the pins of the
connector are fully seated in the housing to en-
sure good contact with the connection at the
motor. When voltage is confirmed at these pins,
replace the connector on the motor.
B. Remove the motor control connector from the fur-
nace control at P5 and apply 24VAC to pins 3 & 4
(see photo). With the door switch closed (motor
powered) and 24VAC on pins 3 & 4, the motor
should start operating at 75% of capacity. If the
motor is operating at a good speed, it is likely not
the motor that is the problem. If the motor is not
operating, verify that the control wiring between
the motor and furnace control (to P5) is good and
that all the pins on both ends are fully seated. If
the wiring connections looks good, and the motor
still will not operate, the motor likely needs to be
replaced.
DIAGNOSTICS
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FIGURE 45
LINE VOLTAGE AND LOW VOLTAGE CONNECTIONS TO THE COMMUNICATING MOTOR
A
B
Diagnostics
