SERVICING
34
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.
RED
RESET
BUTTON
COLOR
IDENTIFYING
Testing Auxiliary Limit Control
WARNING
To avoid possible fire, only reset the auxiliary limit control
once. If it should open a second time, a qualified servicer
must determine why the auxiliary limit opened before reset
-
ting again.
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 oc
-
cur. 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)
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. Mea-
sure 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
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 con-
trol 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.