Goodman GMEC80 Service Instructions Manual page 24

SERVICING
CHECKING TRANSFORMER AND CONTROL
CIRCUIT
A step-down transformer 120 volt primary to 24 volt second-
ary, 40 VA (Heating and Cooling Models) supplies ample
capacity of power for either operation.
HIGH VOLTAGE
D ALL
ISCONNECT POWER BEFORE SERVICING OR
CHANGING ANY ELECTRICAL WIRING.
F
SOURCES MAY BE PRESENT.
PROPERTY DAMAGE, PERSONAL INJURY OR DEATH.
1. Remove blower compartment door to gain access to
the thermostat low voltage wires located at the furnace
integrated control module.
2. Remove the thermostat low voltage wires at the furnace
integrated control module terminals.
With Power On (and Door Interlock Switch closed):
L
INE VOLTAGE NOW PRESENT
3. Use a voltmeter, check voltage across terminals R
and C. Must read 24 VAC.
4. No voltage indicates faulty transformer, open fuse,
bad wiring, bad splice, or open door interlock switch.
5. Check transformer primary voltage at incoming line
voltage connections, fuse, splices, and blower door
interlock switch.
6. If line voltage is available to the primary side of
transformer and not at secondary side, the trans-
former is inoperative. Replace.
7. After completing check and/or replacement of trans-
former and check and/or repair of control circuit, rein-
stall blower compartment door.
8. Turn on electrical power and verify proper unit opera-
tion.
L
INE VOLTAGE NOW PRESENT
HIGH VOLTAGE
D ALL
ISCONNECT POWER BEFORE SERVICING OR
M
INSTALLING THIS UNIT. ULTIPLE POWER SOURCES MAY
F
BE PRESENT. AILURE TO DO SO MAY CAUSE PROPERTY
DAMAGE, PERSONAL INJURY OR DEATH.
24
WARNING
M
ULTIPLE POWER
AILURE TO DO SO MAY CAUSE
WARNING
WARNING
WARNING
CHECKING AIR CIRCULATOR BLOWER MOTOR
(MULTI-SPEED ECM MOTOR)
D ALL
ISCONNECT POWER BEFORE SERVICING.
1. Remove blower compartment door to gain access to the
circulator blower motor and integrated ignition control.
2. Check for any obstruction that would keep the fan wheel
/ fan motor from turning.
3. Check wiring, the motor has two wiring harnesses,
a main harness and a control harness. The main pin
harness has:
White neutral wire connected to the Neutral terminal on
the control board.
Black wire connected to the CIRC H terminal on the
control board.
Red wire connected to the COM terminal, which is a
female spade connection next to the T1 – T4 wires on
the control board.
Green ground wire connected to cabinet ground
The control harness has:
Blue wire connected to T1 on the control board.
Red wire connected to T2 on the control board.
Orange wire connected to T3 on the control board.
Black wire connected to T4 on the control board.
The multi-speed ECM motor requires a line voltage
power supply (black connected to CIRC H and white
connected to neutral on the control board) as well as a
signal on one of the speed taps (T1-T4).
The speed tap voltage is D.C. and can vary depending
on S2 DIP switch selection. The voltage reading from
any one of the speed taps is referenced between the
female COM terminal next to the speed taps on the
control board. From COM to T1 or T2, 6-7 VDC when
energized. From COM to T3, 13-14 VDC when ener-
gized. From COM to T4, 6-7 or 13-14 VDC depending
on S2 settings.
WARNING