SERVICING
33
CHECKING VOLTAGE
WARNING
HIGH VOLTAGE
Disconnect ALL power before servicing or
changing any electrical wiring. Multiple pow
-
er sources may be present. Failure to do so
may cause property damage, personal injury
or death.
1. Remove the burner door on furnaces to gain entry to
the Junction Box.
2. Remove cover from the Junction Box and gain access
to incoming power lines.
With Power ON:
WARNING
Line Voltage now present.
3. 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.
4. No reading - indicates open wiring, open fuse, no pow-
er, or faulty Door Interlock Switch from unit to fused
disconnect service. Repair as needed.
5. With ample voltage at line voltage connectors, ener-
gize the furnace blower motor by jumpering terminals
R to G on the integrated ignition control.
6. With the blower motor in operation, the voltage should
be 115 volts ± 10 percent.
7. 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.
8. After completing check and/or repair, replace Junction
Box cover and reinstall the service panel doors.
9. Turn on electrical power and verify proper unit operation.
CHECKING WIRING
WARNING
Disconnect ALL power before servicing.
1. Check wiring visually for signs of overheating, dam-
aged insulation and loose connections.
2. Use an ohmmeter to check continuity of any suspect-
ed 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.
CHECKING THERMOSTAT, WIRING
WARNING
Disconnect ALL power before servicing.
1. Remove the blower compartment door to gain access
to the thermostat low voltage wires located at the fur-
nace integrated control module terminals.
2. Remove the thermostat low voltage wires at the fur-
nace 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):
WARNING
Line Voltage now present.
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 check-
ing the furnace in the air conditioning mode, proceed
as follows.
7.
With power off, Jumper terminals R to Y to G.
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 wir-
ing. 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.
