18
SERVICING
S-1 CHECKING VOLTAGE
WARNING
HIGH VOLTAGE
Disconnect ALL power before servicing or in
-
stalling this unit. Multiple power sources may
be present. Failure to do so may cause proper
-
ty damage, personal injury or death.
1. Remove the burner door to gain entry to the Junction
Box.
2.
Remove cover from the Junction Box and gain ac
-
cess 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
power, 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 Junc
-
tion Box cover and reinstall the service panel doors.
9.
Turn on electrical power and verify proper unit
operation.
S-2 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 AND
ANTICIPATOR
S-3A THERMOSTAT AND 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
furnace 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 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 checking 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 condens
-
ing 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-3B HEATING ANTICIPATOR
On older thermostats the heating anticipator is a wire wound
adjustable heater which is energized during the “ON” cycle
to help prevent overheating of the conditioned space.
The anticipator is a part of the thermostat and if it should
fail for any reason, the thermostat must be replaced. Some
thermostats have a cycle rate adjustment switch to set cy-
cles per hour.
