48
SERVICING
WARNING
T
O AVOID POSSIBLE FIRE, ONLY RESET THE AUXILIARY LIMIT CONTROL
ONCE.
I
F IT SHOULD OPEN A SECOND TIME, A QUALIFIED SERVICER
MUST DETERMINE WHY THE AUXILIARY LIMIT OPENED BEFORE
RESETTING AGAIN.
S-302 CHECKING FLAME ROLLOUT CONTROL
A temperature activated manual reset control is mounted to
the manifold assembly on 80% furnaces,
ROLLOUT
SWITCH
Flame Rollout Switch Location
(80% Upflow Furnace Shown, Downflow Similar)
The control is designed to open should a flame roll out
occur. An over firing condition or flame impingement on the
heat shield may also cause the control to open. If the rollout
control opens, the air circulation blower will run continuously.
On single-stage 80% the ignition control diagnostic light will
flash (6) six times indicating a trip of the rollout switch. (on
some models this also indicates an open control board fuse)
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 con-
trol. 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.