SERVICING
35
LIMIT
AUXILIARY LIMIT
CONTROL
AUXILIARY LIMIT
CONTROL
BLOWER HOUSING
Auxiliary Limit Control Location
WARNING
H
I
GH
VOLTAGE
D
I
SCONNECT
ALL
P
O
W
E
R
BEFO
R
E SE
R
V
I
C
I
NG O
R
I
NSTALL
I
NG TH
I
S UN
I
T.
M
ULT
IP
LE
P
O
W
E
R
SOU
R
CES MAY
BE
PR
ESENT.
F
A
I
LU
R
E TO
D
O SO MAY CAUSE
PR
O
P
E
R
TY
D
AMAGE,
P
E
R
SONAL
I
N
J
U
R
Y O
R
D
EATH.
1. Remove blower compartment door to gain access to
the auxiliary.
2. Remove the wires from the auxiliary limit control termi-
nals.
3. Using an ohmmeter, test for continuity across the two
terminals.
RED
RESET
BUTTON
COLOR
IDENTIFYING
Testing Auxiliary Limit Control
S-302 Checking Flame Rollout Control
A temperature activated manual reset control is mounted to
the manifold assembly as shown in the following illustration
FLAME
ROLLOUT
SWITCHES
Flame Rollout Switch Location
(90% Upflow Furnace Shown, Counterflow 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.
1. Remove the burner compartment door to gain access to
the rollout switch(es) mounted to burner bracket.
2. Reset the manual roll out switch
3. Remove wires from roll out switch
4. Using an ohmmeter, check for continuity across the switch.
5. If the switch will not close after manually resetting, it must
be replaced.
6. Measure the voltage between each side of the rollout
control and ground during the ignition attempt. If a roll
out switch has tripped, it is important to find out why.
Possible causes could be flame impingement, orifice
plate out of position, burners with excessive cross-over
slot dimension, over-firing, improper orifices, improper
gas pressure, air leaking from around the heat exchanger
into the burner compartment, air leaking through the heat
exchanger itself.
7. After check and/or replacement of rollout switch, reinstall
burner compartment door and verify proper unit operation.