035-17468-001 Rev. A (801)
36
Unitary Products Group
MOTOR STARTS BUT: RUNS ERRATICALLY
•
Check the line voltage for variation.
•
Check low voltage connections at motor, unseated pins
in motor harness connectors.
•
Check “Bk” for erratic CFM command.
MOTOR HUNTS OR “PUFFS”
•
Excessive restriction in duct system or filter. Reduce
maximum air flow.
STAYS AT LOW CFM DESPITE SYSTEM CALL FOR COOL
OR HEAT CFM
•
Check low voltage wires and connections.
•
Verify fan is not in delay mode - wait until delay is com-
plete.
•
“R” missing /not connected at motor or terminal strip.
•
Perform motor/control replacement check.
STAYS AT HIGH CFM
•
“R” missing/not connected at motor or terminal strip.
•
Is fan in delay mode? Wait until delay is complete.
•
Perform motor/control replacement check.
BLOWER WON’T SHUT OFF
•
Current leakage from controls into G, Y, or W? Check for
Triac switched thermostat or solid state relay.
EXCESSIVE NOISE
•
Determine if it’s air noise, cabinet, duct, or motor noise.
AIR NOISE
•
Check for loose blower housing, panels, etc.
•
High static creating high blower speed.
REPLACEMENT OF FAILED MOTOR CONTROL MODULE
NOTE:
The motor control module may be removed and
replaced without voiding the GE warranty.
BLOWER REMOVAL FOR CONTROLLER REPLACEMENT
•
Refer to BLOWER CARE on Page 34 of this manual for
blower removal instructions.
•
Rest the blower on its side so the end of the motor is
accessible and facing up.
•
Wait at least 5 minutes after disconnecting AC power
from the furnace before opening the motor.]
•
Remove the 2-1/4” Hex head bolts from the motor while
holding the control module.
•
Verify with an ohmmeter that the resistance of each
motor lead is greater than 100K ohms by connecting one
meter lead to the motor lead and the other to an
unpainted portion of the motor housing. If any one of the
leads fails this test THE MOTOR IS DEFECTIVE AND
MUST BE REPLACED.
•
Verify that the replacement control module is the correct
one and carefully orient the control module close to the
motor so the cable can be plugged into the module.
BE
SURE THE PLUG LATCHES WITH A CLICK.
•
Carefully align the locating pin of the control module with
the matching motor hole. Replace the 2-1/4” hex head
bolts and tighten snugly. DO NOT OVERTIGHTEN.
REPLACEMENT OF THE VARIABLE SPEED MOTOR
WITH A PSC DIRECT DRIVE MOTOR
NOTE:
A failed variable speed motor should always be
replaced with a variable speed motor suitable for the furnace
model being serviced. However, if one is not available, a 3
speed direct drive motor may be used in the interim.
REMOVAL OF THE VARIABLE SPEED BLOWER ASSEM-
BLY AND MOTOR
Follow the Blower Removal Instructions in the Maintenance
section of this instruction under, BLOWER CARE on Page
34.
1.
Loosen the blower wheel set screw and the motor mount
bolt, and slide the variable speed motor out of the blower
housing.
You must have the correct replacement control mod-
ule for the furnace being serviced. The controls are
factory programmed for specific operating modes.
Consult the parts list supplied with this furnace to
obtain the correct part number before ordering the
part.
Using the wrong control module voids all product
warranties and may produce unexpected results.
When the hex bolts are removed from the control
module, the module is free from the motor but still
connected by a plug and cable. Carefully rotate the
control so as to gain access the plug on the end of
cable. Squeeze the release latch and gently pull the
plug out of the control module. Do not pull on the
wires.
