Lennox ML196DF045XE36B Manual page 16

C- Blower Compartment
IMPORTANT
Each blower is statically and dynamically bal­
anced as an assembly before installation in the
unit.
ML196DFE units are equipped with a constant torque ECM
motor. It has a DC motor coupled to an electronic control
module both contained in the same motor housing. The mo­
tor is programmed to provide constant torque at each of the
five selectable speed taps. Each tap requires 24 volts to en­
ergize.
Input Voltage Requirements
The circuit is designed to be operated with AC voltage. To
enable a tap requires 12 to 33VAC. Expected current draw
will be less than 20mA.
Troubleshooting the Motor
Troubleshooting the motor is an easy process. Follow
steps below.
1- Shut off power to unit.
2- Remove input plugs P48 and P49 from motor. See
figure 16 for troubleshooting procedure.
If correct voltage is present in tests 1 and 2 and motor is not
operating properly, replace motor. The motor is not field re­
pairable.
If replacing the indoor blower motor or blower wheel is nec­
essary, placement is critical. The blower wheel must be cen­
tered in the blower housing as shown in figure 13. When re­
placing the indoor blower motor the set screw must be
aligned and tightened with the motor shaft as shown in figure
14.
9. Secondary Limit Controls
The secondary limit is located in the blower compartment on
the back side of the blower housing. See figure 15. When ex­
cess heat is sensed in the blower compartment, the limit will
open. If the limit is open, the furnace control energizes the sup­
ply air blower and closes the gas valve. The limit automatically
resets when unit temperature returns to normal. The secon­
dary limit cannot be adjusted.
BLOWER WHEEL REPLACEMENT
ALIGN AND TIGHTEN SET SCREW WITH
FLAT SIDE OF MOTOR SHAFT
Set Screw
Housing Hub
Motor
Shaft
SECONDARY LIMIT CONTROL
Page 16
Center Blower Wheel
in Blower Housing
FIGURE 13
FIGURE 14
Secondary Limits
FIGURE 15