service and
333BAV
333JAV
Series B
maintenance procedures
UPFLOW/HORIZONTAL,
VARIABLE-SPEED, 2-STAGE,
INDUCED-COMBUSTION FURNACES
Cancels: SP04-43
SP04-50
10-97
NOTE: Read the entire instruction manual before performing any
service or maintenance.
This symbol → indicates a change since the last issue.
These procedures are for size 60,000 through 120,000 Btuh units.
Index
Page
SAFETY CONSIDERATIONS.....................................................1
ELECTROSTATIC DISCHARGE (ESD) PRECAUTIONS
PROCEDURE...........................................................................2
CARE AND MAINTENANCE..................................................2-5
Air Filter Arrangement..........................................................2-3
Blower Motor and Wheel.........................................................3
Cleaning Heat Exchanger......................................................3-5
Electrical Controls and Wiring.................................................5
Troubleshooting ........................................................................5
Application Wiring Diagrams ..................................................6
Unit Wiring Diagram................................................................7
Service Label ............................................................................8
Troubleshooting Guide .............................................................9
A95137
Fig. 1—Model 333BAV or 333JAV Horizontal
®
SAFETY CONSIDERATIONS
ama
Installing and servicing heating equipment can be hazardous due to
gas and electrical components. Only trained and qualified person-
nel should install, repair, or service heating equipment.
Untrained personnel can perform basic maintenance functions
such as cleaning and replacing air filters. All other operations must
be performed by trained service personnel. When working on
heating equipment, observe precautions in the literature, tags, and
labels attached to or shipped with the unit and other safety
precautions that may apply.
CANADIAN GAS ASSOCIATION
A PPROVED
R
→ Follow all safety codes. In the United States, follow all safety
codes including the National Fuel Gas Code NFPA No. 54-
1996/ANSI Z223.1-1996. In Canada, refer to the current edition of
the National Standard of Canada CAN/CGA-B149.1- and .2-M95
Natural Gas and Propane Gas Installation Codes. Wear safety
glasses and work gloves. Have fire extinguisher available during
start-up and adjustment procedures and service calls.
A94085
Fig. 2—Model 333BAV or
333JAV Upflow
CERTIFICATION OF
MANUFACTURING SITE
Recognize safety information. This is the safety-alert symbol
.
When you see this symbol on the furnace and in instructions or
manuals, be alert to the potential for personal injury.
WARNING: The ability to properly perform mainte-
nance on this equipment requires certain expertise, me-
chanical skills, tools, and equipment. If you do not
possess these items, do not attempt to perform any
maintenance on this equipment other than those proce-
dures recommended in the User’s Manual. A FAILURE
TO FOLLOW THIS WARNING COULD RESULT IN
POSSIBLE DAMAGE TO THIS EQUIPMENT, SERI-
OUS PERSONAL INJURY, OR DEATH.
Understand the signal words DANGER, WARNING, and CAU-
TION. These words are used with the safety-alert symbol. DAN-
GER identifies the most serious hazards which will result in severe
personal injury or death. WARNING signifies a hazard which
could result in personal injury or death. CAUTION is used to
identify unsafe practices which would result in minor personal
injury or product and property damage.
—1—
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TABLE 1—UPFLOW/HORIZONTAL FILTER SIZE INFOR-
MATION (IN.)
Clean as follows:
1. Remove blower access door.
FILTER SIZE†
Side Return Bottom Return
FURNACE
CASING WIDTH
FILTER
TYPE
2. Disconnect blower electrical leads from motor. Squeeze
latches to remove connectors from motor. Disconnect green
ground wire from screw. Note location of wires for reas-
sembly.
14-3/16
21
(1) 16 X 25 X 1* (1) 14 X 25 X 1 Cleanable
(1) 16 X 25 X 1 (1) 20 X 25 X 1* Cleanable
(2) 16 X 25 X 1* (1) 24 X 25 X 1 Cleanable
24-1/2
3. Remove control.
* Factory-provided with the furnace.
† Filters may be field modified as required by cutting and folding the frame as
indicated on the filter.
4. Remove screws holding blower assembly to blower deck
and slide blower assembly out of furnace.
a. Turn off electrical supply before removing blower and
control access doors.
5. Mark blower wheel, motor, and motor support in relation to
blower housing before disassembly to ensure proper reas-
sembly.
b. Release filter retainer from clip at front of furnace
casing. (See Fig. 4.) For side return, clips may be used
on either or both sides of the furnace.
6. Loosen setscrew(s) holding blower wheel on motor shaft.
MOUNTING
SCREWS
7. Remove bolts holding motor and motor mount to blower
housing and slide motor and mount out of housing. Motor
mount belly band need not be removed unless motor is to be
replaced.
DRAFT
SAFEGUARD
SWITCH
CAUTION: The blower wheel should not be dropped or
bent as balance will be affected.
RELIEF
BOX
PRESSURE
SWITCHES
MAIN
LIMIT
SWITCH
8. Remove blower wheel from housing.
a. Mark cutoff plate location to ensure proper reassembly.
b. Remove screws holding cutoff plate and remove cutoff
plate from housing.
c. Lift blower wheel from housing through opening.
MANUAL
RESET
9. Clean blower wheel and motor using a vacuum with soft
brush attachment. Do not remove or disturb balance weights
(clips) on blower wheel blades.
LIMIT
SWITCHES
10. Reinstall blower wheel by reversing items 8 a through c. Be
sure wheel is positioned for proper rotation.
AIRFLOW
SELECTOR
11. Reassemble motor and blower by reversing items 4 through
7.
CONTROL
WASHABLE
FILTER
CAUTION: Be sure the motor is properly positioned in
the blower housing. The motor arrow must point in the
direction of airflow through the furnace after the blower
assembly has been reinstalled in the furnace.
FILTER
RETAINER
12. Reinstall blower assembly in furnace.
A95270
13. Reinstall control. If motor has ground wire, be sure it is
connected as before.
Fig. 4—Upflow/Horizontal Component Identification
c. Slide filter out.
14. Connect blower electrical leads to motor. Please note that
connections are polarized for assembly. DO NOT FORCE.
d. Clean filters by spraying tap water through filter from
opposite direction of airflow.
15. If power choke is attached to blower housing, ensure it is
connected in series with black power lead to motor.
e. Rinse and let dry. Oiling or coating of filter is not
recommended or required.
C. Cleaning Heat Exchanger
f. Place filter in furnace.
The following steps should be performed by a qualified service
technician:
g. Replace blower and control access doors and turn on
electrical supply to furnace.
NOTE: Deposits of soot and carbon indicate the existence of a
problem which needs to be corrected. Take action to correct the
problem.
B. Blower Motor and Wheel
For long life, economy, and high efficiency, clean accumulated dirt
and grease from the blower wheel and motor annually.
The following steps should be performed by a qualified service
technician:
The motors have prelubricated sealed bearings and require no
lubrication.
If it becomes necessary to clean the heat exchanger because of
carbon deposits, soot, etc., proceed as follows:
1. Turn gas and power to furnace to OFF.
2. Remove control and blower access doors.
Remember to disconnect the electrical supply before removing
access doors.
3. Disconnect wires to the following components. Mark wires
to aid in reconnection of:
—3—
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a. Draft safeguard switch.
b. Inducer motor.
NOTE: Be very careful when removing the burner assembly to
avoid breaking the ignitor. See Fig. 6 for the correct ignitor
location.
c. Pressure switch(es).
11
13
32"
32"
d. Limit overtemperature switch(es).
e. Gas valve.
BURNER
f. Hot surface ignitor.
g. Flame-sensing electrode.
h. Wiring connectors leading to control.
CELL
PANEL
4. Remove 2 screws that secure relief box. (See Fig. 4.)
5. Remove 8 screws that secure flue collector box to center
panel. Be careful not to damage sealant.
HOT
SURFACE
IGNITOR
ASSEMBLY
6. Remove complete inducer assembly from furnace, exposing
flue openings.
7. Using field-provided small wire brush, steel spring cable,
reversible electric drill, and vacuum cleaner, clean cells as
follows:
a. Assemble wire brush and steel spring cable.
(1.) Use 48 in. of 1/4-in. diameter high-grade steel
spring cable (commonly known as drain clean-out
or Roto-Rooter cable).
C
IGNITOR
BURNER
L
7
(2.) Use 1/4-in. diameter wire brush (commonly known
as 25-caliber rifle cleaning brush).
8"
C
L
NOTE: The materials needed in items (1.) and (2.) can usually be
purchased at local hardware stores.
IGNITOR
ASSEMBLY
(3.) Insert twisted wire end of brush into end of spring
cable, and crimp tight with crimping tool or strike
with ball-peen hammer. TIGHTNESS IS VERY
IMPORTANT.
A93347
Fig. 6—Position of Ignitor to Burner
(6.) IMPORTANT: Replace screws in center panel to
secure heat exchanger cells before cleaning.
(4.) Remove metal screw fitting from wire brush to
allow insertion into cable.
(7.) Insert brush end of cable in lower opening of cell,
and proceed to clean 2 lower passes of cell in same
manner as 2 upper passes.
b. Clean each heat exchanger cell.
(1.) Attach variable-speed, reversible drill to end of
spring cable (end opposite brush).
(8.) Repeat foregoing procedures until each cell in
furnace has been cleaned.
(2.) Remove cell outlet plates. IMPORTANT: Replace
screws in center panel to secure heat exchanger
cells before cleaning.
(9.) Using vacuum cleaner, remove residue from each
cell.
(3.) Insert brush end of cable into upper opening of cell
and slowly rotate with drill. DO NOT force cable.
Gradually insert at least 36 in. of cable into 2 upper
passes of cell. (See Fig. 5.)
(10.) Using vacuum cleaner with soft brush attachment,
clean burner assembly.
(11.) Reinstall cell outlet plates and screws FIRST;
then, reinstall cell inlet plates and burner assem-
bly. Care must be exercised to center the burners
in the cell openings.
8. After cleaning flue openings, clean flue collector. Check
sealant on flue collector to ensure that it has not been
damaged. If new sealant is needed, contact your dealer or
distributor.
9. Replace flue collector assembly, making sure all 8 screws
are secure.
10. Reinstall relief box.
11. Reconnect wires to the following components:
a. Draft safeguard switch.
b. Inducer motor.
A91252
Fig. 5—Cleaning Heat Exchanger Cell
c. Pressure switches.
(4.) Work cable in and out of cell 3 or 4 times to obtain
sufficient cleaning. DO NOT pull cable with great
force. Reverse drill and gradually work cable out.
d. Limit overtemperature switch(es).
e. Gas valve.
(5.) Remove burner assembly and cell inlet plates.
f. Hot surface ignitor.
—4—
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g. Flame-sensing electrode.
The control in this furnace is equipped with an LED status light to
aid in installation, servicing, and troubleshooting. It can be viewed
through the sight glass or window on the blower access door. The
control indicates status with the LED on continuously, rapid
flashing, or a code composed of 2 digits. (The first digit is the
number of short flashes, the second is the number of longs flashes.)
Refer to the service label on the blower compartment door for code
explanations and useful troubleshooting suggestions. (See Fig. 10.)
h. Wiring connectors leading to control.
12. Reconnect vent pipe to relief box.
13. Replace blower door only.
14. Turn power and gas to ON.
15. Set thermostat and check furnace for proper operation.
16. Verify blower airflow and that airflow rate changes between
heating and cooling.
It is important to note that power to the furnace must not be
interrupted and the furnace blower door must not be removed until
the LED status code(es) is recorded. When power to the control is
interrupted, the status memory is erased.
17. Check for gas leaks.
18. Replace control door.
The control will store up to 5 previous codes but will not store
non-current codes longer than 48 hr. To retrieve previous codes, if
present, no thermostat inputs to the control must be present and all
time delays must expire. Remove 1 of the red main limit wires 1
to 4 sec until the LED light goes out, then reconnect it. (See Fig.
4.) (Do not leave red wire disconnected for longer than 4 sec as the
control will assume an overtemperature condition exits and will
respond with indoor blower operation.) This places the control in
the status recall mode and displays the first code stored in memory.
Record the code and repeat the disconnect and reconnect of the red
wire, recording each code until code 11 is displayed indicating no
additional faults. After the last code is displayed or after 2 minutes
in the code recall mode, the control will return to normal standby
mode.
WARNING: Never use a match or other open flame to
check for gas leaks. Use a soap-and-water solution. A
failure to follow this warning could result in fire, personal
injury, or death.
D. Electrical Controls and Wiring
NOTE: There may be more than 1 electrical supply to unit.
The electrical ground and polarity for 115-v wiring must be
maintained properly. Refer to Fig. 7 and 8 for field wiring
information and to Fig. 9 for unit wiring information. If the
polarity is NOT correct, the furnace control will display rapid
flashing on the status LED and prevent heat operation. The control
system also requires an earth ground for proper operation of the
microprocessor and variable-speed motor.
Use any recorded status codes, the service label, and the trouble-
shooting diagram on the following pages to diagnose and correct
any problem condition.
NOTE: Be aware that measurement of current (amperes) and
power (watts) for the ICM2+ variable-speed motor will be accurate
only when the meter provides true root-mean-square (RMS)
measurements.
E. Troubleshooting
Refer to the service label. (See Fig. 10.) Page 9 contains a
troubleshooting guide. This guide can be a useful tool in isolating
furnace operation problems. Beginning with the word "Start,"
answer each question and follow the appropriate arrow to the next
item.
With power disconnected from unit, check all electrical connec-
tions for tightness. Tighten all screws on electrical connections. If
any smoky or burned connections are noticed, disassemble the
connection, clean all parts and stripped wire, and reassemble
properly and securely. Electrical controls are difficult to check
without proper instrumentation; therefore, reconnect electrical
power to unit and observe unit through 1 complete operating cycle.
The guide will help to identify the problem or failed component.
After replacing any component, verify correct operation sequence.
More information is available in a separate Troubleshooting Guide
for 2-stage gas-fired induced-combustion furnaces.
The 24-v circuit contains an automotive-type, 3-amp fuse located
on the main control. Any 24-v electrical shorts during installation,
service, or maintenance could cause this fuse to blow. If fuse
replacement is required, use ONLY a 3-amp fuse. The control will
display code 24 when the fuse needs replacement.
—5—
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FIELD 24-V WIRING
FIELD 115-, 208/230-, 460-V WIRING
FACTORY 24-V WIRING
FACTORY 115-V WIRING
NOTE 2
1-STAGE
THERMOSTAT
TERMINALS
W
C
Y
R
G
FIVE
WIRE
FIELD-SUPPLIED
FUSED DISCONNECT
THREE-WIRE
HEATING-
ONLY
208/230- OR
460-V
THREE
PHASE
W2
BLK
BLK
COM
W/W1
WHT
WHT
208/230-V
SINGLE
PHASE
GND
NOTE 1
Y/Y2
115-V FIELD-
SUPPLIED
FUSED
JUNCTION
BOX
R
G
GND
CONTROL
CONDENSING
UNIT
DISCONNECT
BOX
NOTE 4
AFS
24-V
TERMINAL
BLOCK
Y1
NOTES: 1. Connect Y/Y2-terminal as shown for proper operation.
2. Some thermostats require a "C" terminal connection as shown.
3. If any of the original wire, as supplied, must be replaced, use
same type or equivalent wire.
FURNACE
4. Y1 is not to be connected.
NOTE 5
5. Connect O to thermostat-O only for heat pump applications.
O
A97588
→ Fig. 7—Heating and Cooling Application Wiring Diagram
for Single-Stage Thermostats and/or Single-Speed Condensing Units
FIELD 24-V WIRING
FIELD 115-, 208/230-, 460-V WIRING
FACTORY 24-V WIRING
FACTORY 115-V WIRING
NOTE 2
2-STAGE
THERMOSTAT
TERMINALS
C
W2 W1 Y2
R
G
Y1
FIELD-SUPPLIED
FUSED DISCONNECT
SEVEN
WIRE
FOUR-WIRE
HEATING-
ONLY
208/230- OR
460-V
THREE
PHASE
W2
BLK
WHT
BLK
COM
W/W1
WHT
208/230-V
SINGLE
PHASE
NOTE 1
GND
C
Y/Y2
115-V FIELD- JUNCTION
Y1
Y2
SUPPLIED
FUSED
BOX
R
G
GND
CONTROL
BOX
2-SPEED
DISCONNECT
CONDENSING
UNIT
AFS
Y1
24-V
TERMINAL
BLOCK
NOTES: 1. Connect Y1 and Y/Y2 as shown for proper operation.
2. Some thermostats require a "C" terminal connection as shown.
3. If any of the original wire, as supplied, must be replaced, use
same type or equivalent wire.
FURNACE
4. Connect O to thermostat-O only for heat pump applications.
NOTE 4
O
A97589
→ Fig. 8—Heating and Cooling Application Wiring Diagram
for 2-Stage Thermostats and/or 2-Speed Condensing Units
—6—
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3 2 2 2 9 3 - 1 0 1 R E V . C
M I D
1 7 T E N O
2
3
4
S W
S W
S W
S C H E M A T I C D I A G R A M
) E N
P R O S P & A L G A
( N A T U R A
B L K
W H
B L U
D
R E
T
K
L
B
N
R
G
U
L
B
E L
Y
E L
Y
N
R
B
E D
R
K
L
B
O I
V
T
W H
T
H
W
N
R
G
B L K
K
L
B
N
R
O
B L K
D
R E
T
W H
8
2
7 9
B L K
Y
G R
3
1
Y
G R
B L K
1 2
1 0 1 1
N
G R
T
W H
E
F S
T
W H
N
B R
1
B L U
6
3
1
2
)
S E U D H E W ( N
T E N O
L
Y E
L
Y E
9
N
O R
N
O R
N
O R
N
O R
D
R E
D
R E
F
F
O F
O N
F
F
O F
O N
F
2
O F
O N
O F
O N
O F
O N
4
3
1
M U D E H
D
R E
Y E L
Y E L
B L U
Y 1
B L K
W H
U
BL
T
N
O
R
O
B L K
B L K
B L K
G R
N
B L U
R E D
R E D
Z E S I
N
O R
Y E L
—7—
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WARNING
Service should be performed only by qualified persons.
SERVICE
If status code recall is needed, do not remove power or blower door.
LED CODE
STATUS
CONTINUOUS OFF Check for 115V at L1 and L2, and 24V at SEC1 and SEC2.
CONTINUOUS ON
RAPID FLASHING
Control has 24V power.
Line voltage polarity reversed. If twinned, 24V power
to one furnace may be out of phase with power to other furnace.
EACH OF THE FOLLOWING STATUS CODES IS A TWO-DIGIT NUMBER WITH
THE FIRST DIGIT DETERMINED BY THE NUMBER OF SHORT FLASHES AND
THE SECOND DIGIT BY THE NUMBER OF LONG FLASHES.
11 NO PREVIOUS CODE - Stored status codes are erased when power (115V or
24V) to control is interrupted or 48 hours after each fault is cleared.
12 BLOWER ON AFTER POWER UP - Blower runs for 90 seconds, if unit is
powered up during a call for heat (R-W/W1 closed). Note: 2-sec. ON-delay.
13 LIMIT OR FLAME ROLL-OUT (FRS) SWITCH LOCKOUT - Auto-reset after
three hours. FRS switch requires manual-reset.
Check for: - Refer to #33
14 IGNITION LOCKOUT - Control will auto-reset after three hours. Refer to #34.
21 GAS HEATING LOCKOUT - Control will NOT auto-reset.
Check for: - Mis-wired gas valve
- Defective control (valve relay)
22 ABNORMAL FLAME-PROVING SIGNAL - Flame is proved while gas valve is
de-energized. Inducer will run until fault is cleared.
Check for: - Leaky gas valve
- Stuck-open gas valve
23 LOW- OR HIGH-HEAT PRESSURE SWITCH DID NOT OPEN
Check for: - Obstructed pressure tubing
- Defective pressure switch (stuck closed)
24 SECONDARY VOLTAGE FUSE IS OPEN
Check for: - Short-circuit in secondary voltage (24V) wiring
31 HIGH-HEAT PRESSURE SWITCH OR RELAY DID NOT CLOSE OR
REOPENED
Check for: -Control relay may be defective - Refer to #32
32 LOW-HEAT PRESSURE, DRAFT SAFEGUARD , OR AUX-LIMIT
(DOWNFLOW ONLY*) SWITCH DID NOT CLOSE OR REOPENED
Check for: - Proper vent sizing (and condensate pitch with side-wall vent)
- Low inducer voltage (115v)
- Defective inducer motor
- Excessive wind
* Blower motor and capacitor
- Defective pressure switch
- Restricted vent
- Inadequate combustion air supply
- Disconnected or obstructed pressure tubing
33 LIMIT OR FLAME ROLL-OUT (FRS) SWITCH IS OPEN - FRS switch
requires manual-reset.
Check for: - Inadequate combustion air supply (FRS switch only)
- Dirty filter or restricted duct system
- Defective switch or connections
- Loose blower wheel
- Blower motor or capacitor failure
34 IGNITION-PROVING FAULT - Control will retry three times before lockout #14.
Check for: - Oxide buildup on flame-proving sensor (clean with fine sandpaper).
- Proper flame-proving microamps (0.5 minimum)
- Proper control ground continuity
- Flame-proving sensor must be ungrounded
- Smooth flame carryover and ignition
- Manual valve(s) OFF
43 LOW-HEAT PRESSURE, DRAFT SAFEGUARD, OR AUXILIARY LIMIT
SWITCH OPEN WHILE HIGH-HEAT PRESSURE SWITCH IS CLOSED
Check for: - Disconnected or obstructed pressure tubing
- Defective pressure switch (stuck open)
- Refer to #32 and #33
45 REPLACE CONTROL
320893-101 REV. A
A94169
Fig. 10—Service Label
—8—
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TROUBLESHOOTING
GUIDE
NOTES:
WARNING
!
1. Refer to information label on blower compartment door
for procedure for use of LED status codes and problem
solving suggestions.
2. LED indicator is viewed through window in blower
compartment door.
ELECTRICAL SHOCK HAZARD
3. If 115-vac power is de-energized or interrupted during
a call for heat, the indoor blower will run for 90 sec
before a gas heating cycle begins – Code 12.
4. After replacing any component, verify correct operating
sequence.
ONLY QUALIFIED AND TRAINED
SERVICE PERSONNEL SHOULD
PERFORM THIS PROCEDURE
If LED is flashing rapidly, check line voltage polarity.
If Code 24 is displayed, check for blown fuse.
If LED is OFF, check line voltage and 24-v transformer.
If Code 45 is displayed, replace control.
START
24v should be present across R
and C. If not, check for:
1. Open flame rollout switch
(FRS) – Code 33.
2. Open limit switch (LS) –
Code 33.
Yes
Turn thermostat OFF.
Is indoor blower on ?
No
On furnace control, note current
settings for setup switches 1 (SW-1)
and 2 (SW-2) then set SW-1 to OFF
and SW-2 to ON.
24v should be present across C and W. If not, check for:
1. Open thermostat.
2. Open 24-v fuse (FU1) – Code 24.
3. Failed transformer.
3. Check all low-voltage wiring
connections.
No
If Code 23 is displayed, the pressure switch(es) is stuck closed.
Replace switch and/or check pressure tube for blockage.
Cycle 115-v power
off for 3 sec, then on.
No
Replace control only if all checks
are OK.
System malfunction – Code 21.
115v should be present at the inducer motor. If so, replace inducer
motor. If not, check 115-v wiring.
No
Continuous LED?
Yes
If Code 32 is displayed check for:
1. Open gas inlet pressure switch (when used).
2. Open pressure switch (LPS) and/or tube – Code 32.
3. Open draft safeguard switch (DSS) – Code 32.
4. Open auxiliary switch (ALS)(downflow only) – Code 32.
5. Check all low-voltage wiring connections.
Set thermostat to call for heat.
Set FAN to AUTO.
No
Replace control only if Code 45 is
displayed, or if all checks are OK.
No
Draft inducer motor starts.
115v should be present at the ignitor. If so, replace the ignitor; if not,
check 115-vac wiring to ignitor.
Yes
LPS, DSS, or ALS open while HPS is closed (high-gas-heat only) –
Code 43.
No
Is Code 22 displayed?
Yes
Control will attempt to light burners 4 times (approximately 1 minute
between attempts – Code 34). Voltage is present at the gas valve for 7
sec during each ignition trial. System will lockout after 4 attempts.
Flame present when not normal.
Replace gas valve.
Is the gas valve control knob in the OPEN or ON position?
24v should be present across the gas valve terminals C and M/P
(and C and HI for high-stage test) during the 7 sec ignition trial. If
not, check all low-voltage wiring connections to valve.
15-sec inducer pre-purge.
Yes
If 24v are present, and main gas does not flow:
1. Is supply pressure between 4.5- and 13.6-in. wc? If not,
adjust supply pressure.
2. If supply pressure is between 4.5- and 13.6-in. wc, replace
gas valve.
No
Replace control only if Code 45 is
displayed, or if all checks are OK.
No
Ignitor warms up and glows
orange/yellow; 17-sec warm-up.
Yes
Check ignitor position.
No
Main burners ignite.
Check burner carryover gap.
Check manifold pressure (1.3- to 1.7-in. wc for low-stage gas
heat; 3.2- to 3.8-in. wc for high-stage gas heat).
Yes
Check for proper orifice size.
Is Code 31 (high-gas-heat only), 32, 33, or 34 displayed? Check
code information label to diagnose.
Replace control if Code 45 is dis-
played, or if all checks are OK.
Clean flame sensor if microamps
are below nominal.
No
No
Check polarity of 115-v power at J-box and control – Rapid
flashing LED.
Main burners stay on.
Yes
Check ground continuity from J-box to control.
Check flame sensor microamps (4.0 nominal; 0.5 minimum for
control to recognize flame).
Indoor blower motor starts on
heating speed after 45-sec
warm-up period.
No
See 2-Stage Gas-Fired Induced-Combustion Furnaces
Troubleshooting Guide (PSC and ICM Blower Motors).
Yes
If not, check for:
1. Satisfied thermostat.
2. Open inlet gas pressure switch (when used).
3. Open pressure switch (LPS) – Code 32.
4. Open draft safeguard switch (DSS) – Code 32.
5. Open auxiliary limit (ALS)(downflow only) – Code 32.
6. Open 24-v fuse (FU1) – Code 24.
7. Open limit switch (LS) – Code 13 or 33.
8. Open flame rollout switch (FRS) – Code 13 or 33.
9. Check 115-v line voltage – LED off.
No
No
No
Furnace runs until call for
heat ends.
No
Replace control only if Code 45 is
displayed, or if all checks are OK.
Yes
Turn thermostat to OFF; gas valve
shuts off burners; 5-sec inducer
post purge.
Check for sources of electrical noise interference (electronic air
cleaners, nearby TV, or radio antennas).
Yes
Indoor blower motor stops after
90, 135, 180, or 225 sec.
If inducer and burners continue to operate, check for 24v at the
gas valve. If 24v are present, verify that the thermostat is open
across R and W. If no voltage is present, turn the gas valve
control knob to the OFF position. Replace gas valve.
No
No
Replace control only if Code 45 is
displayed, or if all checks are OK.
Yes
Heating sequence of operation
complete. Remove blower door,
move setup switch 1 (SW-1) to ON
position and repeat process to check
high-stage gas heat operation.
(When finished return SW-1 and
SW-2 to original desired settings.)
24v should be present across R and C. If not, check for:
1. Open limit switch (LS) – Code 13 or 33.
2. Open flame rollout switch (FRS) – Code 13 or 33.
Replace control only if Code 45 is
displayed, or if all checks are OK.
24v should not be present across R and G. If so, turn thermostat
FAN switch to AUTO.
A96062
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SERVICE TRAINING
Packaged Service Training programs are an excellent way to increase your
knowledge of the equipment discussed in this manual, including:
• Unit Familiarization
• Installation Overview
• Maintenance
• Operating Sequence
A large selection of product, theory, and skills programs is available, using popular
video-based formats and materials. All include video and/or slides, plus companion
book.
Classroom Service Training plus "hands-on" the products in our labs can mean
increased confidence that really pays dividends in faster troubleshooting, fewer
callbacks. Course descriptions and schedules are in our catalog.
CALL FOR FREE CATALOG 1-800-962-9212
[ ] Packaged Service Training
[ ] Classroom Service Training
A94328
© 1997 Bryant Heating & Cooling Systems 7310 W. Morris St. Indianapolis, IN 46231
Printed in U.S.A.
sp0450
Catalog No. 5333-301
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