SERVICING
31
S-1 Checking Voltage
WARNING
H
I
GH
VOLTAGE
D
I
SCONNECT
ALL
P
O
W
E
R
BEFO
R
E SE
R
V
I
C
I
NG O
R
CHANG
I
NG ANY ELECT
RI
CAL
WIRI
NG.
M
ULT
IP
LE
P
O
W
E
R
SOU
R
CES MAY BE
PR
ESENT.
F
A
I
LU
R
E TO
D
O SO MAY CAUSE
PR
O
P
E
R
TY
D
AMAGE,
P
E
R
SONAL
I
N
J
U
R
Y O
R
D
EATH.
1. Remove cover from the Junction Box and gain access to
incoming power lines.
With Power ON:
L
I
NE VOLTAGE NO
W
PR
ESENT
WARNING
2. Using a voltmeter, measure the voltage across the hot
and neutral connections.
NOTE:
To energize the furnace, the Door Interlock Switch
must be engaged at this point.
3. No reading - indicates open wiring, open fuse, no
power, or faulty Door Interlock Switch from unit to fused
disconnect service. Repair as needed.
4. With ample voltage at line voltage connectors, energize
the furnace blower motor by jumpering terminals R to
G on the integrated ignition control.
5. With the blower motor in operation, the voltage should
be 115 volts ± 10 percent.
6. If the reading falls below the minimum voltage, check
the line wire size. Long runs of undersized wire can
cause low voltage. If wire size is adequate, notify the
local power company of the condition.
7. After completing check and/or repair, replace Junction
Box cover and reinstall the service panel doors.
8. Turn on electrical power and verify proper unit
operation.
S-2 Checking Wiring
D
I
SCONNECT
ALL
P
O
W
E
R
BEFO
R
E SE
R
V
I
C
I
NG.
WARNING
1. Check wiring visually for signs of overheating, damaged
insulation and loose connections.
2. Use an ohmmeter to check continuity of any suspected
open wires.
3. If any wires must be replaced, replace with AWM, 105°C.
2/64 thick insulation of the same gauge or its equivalent.
S-3A Checking Thermostat And Wiring
D
I
SCONNECT
ALL
P
O
W
E
R
BEFO
R
E SE
R
V
I
C
I
NG.
WARNING
1. Remove the blower compartment door to gain access to
the thermostat low voltage wires located at the furnace
integrated control module terminals.
2. Remove the thermostat low voltage wires at the furnace
control panel terminal board.
3. Jumper terminals R to W (or W1 and W2 for two-stage
models) on the integrated ignition control.
With Power On (and Door Interlock Switch closed):
L
I
NE VOLTAGE NO
W
PR
ESENT
WARNING
4. Induced Draft Motor must run and pull in pressure
switch.
5. If the hot surface ignitor heats and at the end of the
ignitor warm-up period the gas valve opens and the
burners ignite, the trouble is in the thermostat or wiring.
6. With power off, check the continuity of the thermostat
and wiring. Repair or replace as necessary.
If checking the furnace in the air conditioning mode, proceed
as follows.
7. With power off, Jumper terminals R to Y
8. Turn on the power.
9. If the furnace blower motor starts and the condensing
unit runs, then the trouble is in the thermostat or wiring.
Repair or replace as necessary.
10. After completing check and/or repair of wiring and
check and/or replacement of thermostat, reinstall
blower compartment door.
11. Turn on electrical power and verify proper unit
operation.
S-4 Checking Transformer And Control Circuit
A step-down transformer 120 volt primary to 24 volt secondary,
40 VA (Heating and Cooling Models) supplies ample capacity
of power for either operation.
WARNING
H
I
GH
VOLTAGE
D
I
SCONNECT
ALL
P
O
W
E
R
BEFO
R
E SE
R
V
I
C
I
NG O
R
CHANG
I
NG ANY ELECT
RI
CAL
WIRI
NG.
M
ULT
IP
LE
P
O
W
E
R
SOU
R
CES MAY BE
PR
ESENT.
F
A
I
LU
R
E TO
D
O SO MAY CAUSE
PR
O
P
E
R
TY
D
AMAGE,
P
E
R
SONAL
I
N
J
U
R
Y O
R
D
EATH.
1. Remove blower compartment door to gain access to
the thermostat low voltage wires located at the furnace
integrated control module.
