Service Manual

54
SERVICING
S-1 CHECKING VOLTAGE
WARNING
HIGH VOLTAGE
D
ISCONNECT ALL POWER BEFORE SERVICING OR
CHANGING ANY ELECTRICAL WIRING.
MULTIPLE POWER
SOURCES MAY BE PRESENT.
FAILURE TO DO SO MAY CAUSE
PROPERTY DAMAGE, PERSONAL INJURY OR DEATH.
1. Remove the blower door to gain entry to the Junction
Box.
2. Remove cover from the Junction Box and gain access
to incoming power lines.
With Power ON:
L
INE VOLTAGE NOW PRESENT
WARNING
3. Using a voltmeter, measure the voltage across the hot
and neutral connections. Line voltage should measure
115 +/- 10%. Measure from black (hot) to ground should
also read 115 volts +/- 10%. Measuring from white (neu-
tral) to ground should read 0 volts
NOTE: To energize the furnace, the Door Interlock Switch
must be engaged at this point.
4. No reading - indicates open wiring, open line voltage
fuse, no power, or faulty Door Interlock Switch from
unit to fused disconnect service. Repair as needed.
5. With proper voltage at line voltage connectors, ener-
gize the furnace blower motor by jumpering termi-
nals 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 opera-
tion.
S-2 CHECKING WIRING
DISCONNECT ALL POWER BEFORE SERVICING.
WARNING
1. Check wiring visually for signs of overheating, dam-
aged 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 equiva-
lent.
CHECKING THERMOSTAT, WIRING
AND ANTICIPATOR
S-3A THERMOSTAT AND WIRING
DISCONNECT ALL POWER BEFORE SERVICING.
WARNING
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 on the integrated ignition
control.
With Power On (and Door Interlock Switch closed):
NOTE: For this test, DIP switch #13 must be in OFF posi-
tion.)
LINE VOLTAGE NOW PRESENT
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 thermo-
stat 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 (or Y1 or Y2
for two-stage models) 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 opera-
tion.