48
SERVICING
L
INE VOLTAGE NOW PRESENT
WARNING
1. Remove the burner compartment door to gain access to
the rollout switch(es) mounted to burner bracket.
The servicer should reset the ignition control by opening and
closing the thermostat circuit. Then look for the ignitor glowing
which indicates there is power to the ignition control. Measure
the voltage between each side of the rollout control and ground
while the ignition control tries to power the gas valve.
2. Measure the voltage between each side of the rollout
control and ground during the ignition attempt. Refer to
the following figure.
VOLT / OHM
METER
GN
D
RED
RESET
BUTTON
COLOR
IDENTIFYING
TAB
Checking Flame Rollout Switch
a. If no voltage is measured on either side of control it
indicates ignition control or wiring to control problem.
b. If voltage is measured on one side of the control and
not the other it indicates the control is open.
c. If voltage is measured on both sides of the control the
wiring to gas valve or valve is at fault.
3. After check and/or replacement of rollout switch, reinstall
burner compartment door and verify proper unit operation.
S-303 INDUCED DRAFT BLOWER MOTOR
WARNING
HIGH
VOLTAGE
D
ISCONNECT
ALL
POWER BEFORE SERVICING OR
INSTALLING THIS UNIT.
M
ULTIPLE POWER SOURCES MAY
BE PRESENT.
F
AILURE TO DO SO MAY CAUSE PROPERTY
DAMAGE, PERSONAL INJURY OR DEATH.
1. Remove burner compartment door to gain access to the
induced draft blower motor.
2. Disconnect the motor wire leads from its connection
point at the induced draft motor.
3. Using a ohmmeter, test for continuity between each of
the motor leads.
4. Touch one probe of the ohmmeter to the motor frame
(ground) and the other probe in turn to each lead.
If the windings do not test continuous or a reading is
obtained to ground, replace the motor.
5. If the windings have a continuity reading, reconnect
wires. Turn power on to the furnace and turn the
thermostat on in the heating mode. Check voltage for
115V at the induced draft motor terminals during the
trial for ignition. If you have 115V and the motor does
not run, replace the induced draft motor.
6. After completing check and/or replacement of induced
draft motor, reinstall burner compartment door.
7. Turn on electrical power and verify proper unit opera
-
tion.
S-304 CHECKING GAS VALVE (REDUNDANT)
A combination redundant operator type gas valve which
provides all manual and automatic control functions required
for gas fired heating equipment is used.
The valve provides control of main burner gas flow, pressure
regulation, and 100 percent safety shut-off.
WARNING
D
ISCONNECT
ALL
POWER BEFORE SERVICING
Single stage gas valves should be tested on the furnace with
24 VAC connected to the gas valve and manometers reading
supply line and manifold pressures.
S-305 CHECKING MAIN BURNERS