SERVICING
37
WARNING
Do not bypass any safety circuit.
CHECKING FLAME ROLLOUT CONTROL
A temperature activated manual reset control is mounted to
the manifold assembly on 90% furnaces, as shown in the
following illustrations.
Should read continuous unless heat exchanger temperature
is above limit control setting. If not as above, replace the
control.
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2
FLAME
ROLLOUT
SWITCHES
Flame Rollout Switch Location
The control is designed to open should a flame roll out oc
control opens, the air circulation blower will run continuously.
On single-stage models, the ignition control diagnostic light
will flash (6) six times indicating a trip of the rollout switch or
an open control board fuse.
To aid in identifying these controls, color-coded labels have
been affixed to the back of these controls. Refer to the Roll
-
out Limit Charts in furnace Technical Manual for tempera-
ture settings and color codes.
WARNING
Line Voltage now present.
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.
RED
RESET
BUTTON
COLOR
IDENTIFYING
Checking Flame Rollout Switch
a. If no voltage is measured on either side of con-
trol 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, rein-
stall burner compartment door and verify proper unit
operation.
INDUCED DRAFT BLOWER MOTOR
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 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.
