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  3. IDL

Hayward IDL, ED2, IDL2, UHS Fault Code Thumbnails

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Heater System Solving Guide
FAULT CODE THUMBNAILS – PAGE F 1
FAULT CODE THUMBNAILS – PAGE F 1
Fault Code Thumbnails
FAULT CODE THUMBNAILS
Heater System Solving Guide
FAULT CODE THUMBNAILS – PAGE F 2
FAULT CODE THUMBNAILS – PAGE F 2
Heater System Solving Guide
Fault Code Thumbnails AC Blower Vacuum Switch – Failed Closed
FAULT CODE THUMBNAILS AC BLOWER VACUUM SWITCH – FAILED CLOSED
UHS
AC
BLOWER VACUUM SWITCH – FAILED CLOSED
If the blower vacuum switch is closed before blower start-up,
the control module will not start the blower.
Pre-check is executed by the control module.
PARTS THAT MAY BE NEEDED
• Blower Vacuum Switch
• Control Module.
DIAGNOSTIC SEQUENCE
A. Disconnect the blower plug from the control module.
With the heater off, measure the control module receptacle’s
continuity across pins 1 and 2 (UHS, IDL2 & IDL) and pins 3 & 4
(IDL2 & IDL only). If either is closed, replace the control module.
B. If the relay is open, check the vacuum switch. If it is closed,
the blower vacuum switch failed and must be replaced.
IDL
IDL2
FAULT CODE THUMBNAILS – PAGE F 3
FAULT CODE THUMBNAILS – PAGE F 3
Heater System Solving Guide
Fault Code Thumbnails AO Blower Vacuum Switch – Failed Open
FAULT CODE THUMBNAILS AO BLOWER VACUUM SWITCH – FAILED OPEN
UHS
IDL2
IDL
AO
BLOWER VACUUM SWITCH – FAILED OPEN
If the blower vacuum switch opens unexpectedly during operation, the
heater will shut down and attempt to re-light if there is still a call for
heat. If the blower vacuum switch does not close after the blower starts,
the control will stop the ignition trial & go into lockout. The blower will
continue to run for post-purge.
Automatic reset is immediate after the switch closes.
PARTS THAT MAY BE NEEDED
• Blower • Control Module/Ignition Board
• Blower Vacuum Switch • Gray Vacuum Tubing
DIAGNOSTIC SEQUENCE
A. Check for faulty vacuum switch tubing and replace if necessary.
B. Check for faulty vacuum switch wiring or connection. Wire harness
terminals must be securely fastened to spade terminals on vacuum switch.
C. Check for faulty blower wiring or connection. Plug on blower must be
securely fastened to control module.
D. Check for defective vacuum switch by disconnecting blower plug
from control module. Measure resistance across blower windings.
Winding resistance across lead should be in the following range:
IDL: Black to White 30-45 ohms Red to White 90-130 ohms
IDL2: Black to White 10-14 ohms Red to White 18-22 ohms
UHS: Red to White 8-9 ohms
If measured values vary substantially from these values,
the blower is defective and should be replaced.
E. Check for a defective blower relay by disconnecting blower plug from
the control module. Place heater in Pool or Spa mode. Lower set point
temperature to generate call for heat. During pre-purge period, measure
for 120VAC across pins 1 and 2 (UHS & IDL2) or L1 & IND low (IDL).
If 120VAC is not present, the control module relay is defective, which
means the control module must be replaced.
F. If the above steps do not resolve the problem (the error still exists),
the vacuum switch is defective and must be replaced.
Heater System Solving Guide
FAULT CODE THUMBNAILS – PAGE F 4
FAULT CODE THUMBNAILS – PAGE F 4
Heater System Solving Guide
Fault Code Thumbnails BD Bad Board or Secondary High Voltage Fault
FAULT CODE THUMBNAILS BD BAD BOARD OR SECONDARY HIGH VOLTAGE FAULT
UHS
IDL2
BD
BAD BOARD
OR
SECONDARY HIGH VOLTAGE FAULT
PARTS THAT MAY BE NEEDED
• Control Module / Ignition Board
• Extra Fuses
• Fuse Board
• Wiring Harness
• Transformer
DIAGNOSTIC SEQUENCE
A. Verify that FC4 fuse on fuse board is not open. Remove FC from fuse-
holder. Measure continuity across fuse. If OK, reinstall fuse and proceed
to step 2. If fuse is open, proceed to section titled “Open FC4 Fuse”.
B. Verify high voltage output from fuse board. Disconnect plug from P6
connector of fuse board. Measure for 120VAC across pins 3 and 5 of
P6 receptacle on fuse board. If OK, reconnect plug and proceed to step
3. If not OK, go to step 4.
C. Check for defective wiring harness. Disconnect plug from E10 connector
of contol module. Measure for 120VAC across pins 1 and 3 of plug on
wiring harness. If OK, replace control module. If not OK, replace wiring
harness.
D. Check for defective transformer. Disconnect plug from P4 connector of
fuse board. Measure for 120VAC between pins 4 and 6 of plug from
transformer. If OK, proceed to step 5. If not OK, replace transformer.
E. If the above steps have not resolved the error condition, the fuse board
is defective and must be replaced.
NOTE: Red letters above correspond with adjacent illustrations.
FAULT CODE THUMBNAILS – PAGE F 5
FAULT CODE THUMBNAILS – PAGE F 5
Heater System Solving Guide
Fault Code Thumbnails BO Bypass Operation (for external controls)
FAULT CODE THUMBNAILS BO BYPASS OPERATION (FOR EXTERNAL CONTROLS)
BO
BYPASS OPERATION (FOR EXTERNAL CONTROLS)
UHS, IDL2, IDL, ED2
The “bo” code is more of an information code than a fault code,
with the “bo” standing for Bypass Operation.
A “bo” code indicates the heater’s internal thermistor is disabled,
allowing the external thermostat control to operate.
This prevents any confusion between the two temperature-sensing
devices during heater operation — though the heater’s thermistor
will still prevent the heater for exceeding 104
o
F.
Heater System Solving Guide
FAULT CODE THUMBNAILS – PAGE F 6
FAULT CODE THUMBNAILS – PAGE F 6
Heater System Solving Guide
Fault Code Thumbnails CE Communication Error
FAULT CODE THUMBNAILS CE COMMUNICATION ERROR
UHS
IDL2
CE
COMMUNICATION ERROR
PARTS THAT MAY BE NEEDED
• Control Module/Ignition Board
•. Display Board
• Membrane Switch/Keypad.
ERROR DETAIL: COMMUNICATION ERROR
BETWEEN CONTROL MODULE & DISPLAY INTERFACE ASSEMBLY
If communication between the ignition board and the display board is
not established within 3 seconds of power-up, an error will be displayed.
After communication is established, if it is lost for 30 seconds, the er-
ror will be displayed. The error code will be cleared upon a valid data
exchange between boards..
DIAGNOSTIC SEQUENCE
A. Power down heater and re-power. This is similar to rebooting a com-
puter.
B. If rebooting does not solve the problem, inspect the display interface
wiring. Ensure the display interface plug is securely attached to the
control module.
C. If steps A & B do not resolve the CE error, the control module and/or
display interface assembly are defective and must be replaced.
FAULT CODE THUMBNAILS – PAGE F 7
FAULT CODE THUMBNAILS – PAGE F 7
Heater System Solving Guide
Fault Code Thumbnails EE Electrical Error
FAULT CODE THUMBNAILS EE ELECTRICAL ERROR
EE
ELECTRICAL ERROR
PARTS THAT MAY BE NEEDED
• Control Module / Ignition Board
DIAGNOSTIC SEQUENCE
Replace the Control Module / Ignition Board.
UHS
IDL2
Heater System Solving Guide
FAULT CODE THUMBNAILS – PAGE F 8
FAULT CODE THUMBNAILS – PAGE F 8
Heater System Solving Guide
Fault Code Thumbnails HF NEW: Gas Valve Fault or OLD: Heater Flame Sensing Fault
FAULT CODE THUMBNAILS HF FLAME PRESENT WITH GAS VALVE CLOSED / HEATER FLAME SENSING FAULT
UHS
IDL2
ED2
IDL
HF
HEATER FLAME SENSING FAULT
IDL, ED2
PARTS THAT MAY BE NEEDED
• Ignitor / Flame Sensor
• Control Module / Ignition Board
DIAGNOSTIC SEQUENCE
A. Check all wiring and connections for Flame sensor.
B. Replace flame sensor (IDL) or ignitor (ED2).
C. Replace control module/ignition board if problem still exists.
HF
FLAME PRESENT WITH GAS VALVE CLOSED
UHS, IDL2
PARTS THAT MAY BE NEEDED
• Gas Valve
If flame is sensed without the gas valve energized, the control will go
into lockout.
DIAGNOSTIC SEQUENCE
• SHUT OFF GAS TO HEATER IMMEDIATELY.
• The gas valve is defective and needs to be replaced.
RIGHT: HF INDICATES A FLAME SENSING FAULT ON OLDER MODELS (IDL, ED2)
BELOW: HF INDICATES A GAS VALVE FAULT ON NEWER MODELS (UHS, IDL2)
FAULT CODE THUMBNAILS – PAGE F 9
FAULT CODE THUMBNAILS – PAGE F 9
Heater System Solving Guide
Fault Code Thumbnails HS Maximum Return Water Temp Exceeded
FAULT CODE THUMBNAILS HS MAXIMUM RETURN WATER TEMP EXCEEDED
HS
MAXIMUM RETURN WATER TEMPERATURE EXCEEDED
UHS, IDL2, IDL, ED2
If water temperature exceeds 105°F, the heater will shut down and
go into lock-out.
Automatic restart is 2 minutes after water temp drops below 105°F.
PARTS THAT MAY BE NEEDED
• Control Module
• External Thermostat (if system uses one)
NOTE: In most cases, no replacement part will be needed.
DIAGNOSTIC SEQUENCE
A. Verify water flow is adequate.
Low water flow will cause high temperature.
(Generally, 25 gpm is needed by smaller heaters, while 300,000 btu/h
heaters may require 40 gpm or more. See heater’s operating manual.)
B. Verify set point setting of remote thermostat us below 108°F. If external
control is used, verify that external thermostat is set below 104
o
F. (Exter-
nal thermostat may be faulty and need to be replaced.)
C. Verify integrity of exchanger.
D. Check for possible bad ignition/control module.
Heater System Solving Guide
FAULT CODE THUMBNAILS – PAGE F 10
FAULT CODE THUMBNAILS – PAGE F 10
Heater System Solving Guide
Fault Code Thumbnails IF Ignition Failure
FAULT CODE THUMBNAILS IF IGNITION FAILURE (INSUFFICIENT FUEL)
IF
IGNITION FAILURE
(INSUFFICIENT FUEL)
UHS, IDL2, IDL, ED2
REQUIRED DIAGNOSTIC TOOLS
• Manometer
• Multimeter
PARTS THAT MAY BE NEEDED
• Flame Sensor
• Ignitor
• Ignition Board / Control Module
• Gas Valve
While IF actually stands for Ignition Failure, this code is often
referred to as the Insufficient Fuel code – since the most common
reason for an “IF” code is inadequate gas supply to the heater.
—————
“IF” occurs when the heater passes all safety checks but the heater fails to
ignite.
Without the proper gas/air mixture, the heater will not light. Since the
heater has gone through most of the steps within the Sequence of Op-
eration, the problem is most likely gas supply or a faulty ignition board,
flame sensor, ignitor or gas valve.
Investigate and ensure that the gas train is correct.
The source of an IF code is found in the gas train 90% of the time.
DIAGNOSTIC SEQUENCE
A. Ensure that main gas shutoff adjacent to heater is open. Ensure that
knob on gas valve inside unit is in ‘‘on’’ position. If OK, proceed to
next step.
B. Check for low gas supply pressure by ensuring inlet gas supply pres-
sure is between the minimum and maximum values indicated on rating
plate. If OK, proceed to next step.
C. Inspect flame sense wiring, and ensure wire harness terminals are se-
curely fastened to flame sense and to control module. If OK, proceed
to next step.
D. Inspect gas valve wiring, and ensure wire harness terminals are se-
curely fastened to spade terminals on gas valve. If OK, proceed to next
step.
E. Check for gas valve failure or gas valve relay failure.1. Measure volt-
age across gas valve during trial for igintion.
I. If 24VAC is present and gas valve does not open, gas valve is de-
fective and must be replaced.2.
II. If 24VAC is not present, gas valve relay on control module is defec-
tive, which means the control module must be replaced.
F. Inspect gas orifices for blockages that could prevent gas flow. Also re-
move and inspect burners for blockages.
FAULT CODE THUMBNAILS – PAGE F 11
FAULT CODE THUMBNAILS – PAGE F 11
Heater System Solving Guide
Fault Code Thumbnails IO Ignitor Failure
FAULT CODE THUMBNAILS IO IGNITOR FAILURE
IO
IGNITOR FAILURE
PARTS THAT MAY BE NEEDED
• Ignitor
• Control Module / Ignition Board
DIAGNOSTIC SEQUENCE
A. Check for faulty wiring or connection.
B. Replace ignitor.
C. Replace Control Module/Ignition Board
NOTE: Red letters above correspond with adjacent illustrations.
IDL2
UHS
B
C
B
C
Heater System Solving Guide
FAULT CODE THUMBNAILS – PAGE F 12
FAULT CODE THUMBNAILS – PAGE F 12
Heater System Solving Guide
Fault Code Thumbnails LO Switch Open within Safety Limit String
UHS
(SEE PAGE F13)
IDL2
(SEE PAGE F13)
IDL
(SEE PAGE F14)
ED2
(SEE PAGE F15)
FAULT CODE THUMBNAILS LO SWITCH OPEN WITHIN SAFETY LIMIT STRING
LO SWITCH OPEN WITHIN SAFETY LIMIT STRING
FAULT CODE THUMBNAILS – PAGE F 13
FAULT CODE THUMBNAILS – PAGE F 13
Heater System Solving Guide
Fault Code Thumbnails LO Switch Open within Safety Limit String (UHS, IDL2)
LO
SWITCH OPEN WITHIN SAFETY LIMIT STRING
UHS, IDL2
PARTS THAT MAY BE NEEDED
• High Limit Switches • Control Module
• (Water) Pressure Switch • Wiring Harness
• Vent Pressure Switch
NOTE: “lo” is normal when pump is off. Otherwise, “lo” means a con-
trol loop switch is open. Therefore, check for the following:
DIAGNOSTIC SEQUENCE
Possibility 1: Water Pressure Switch Fault
A. To verify that the pump is running, turn the pump OFF and watch to see that
the LO code clears. If LO does not clear, proceed to next step.
B. Verify that water flow rate to heater is above minimum required:
20 GPM for H150--- and H200---,
25 GPM for H250--- and H300---,
30 GPM for H350--- and H400---.
If OK, proceed to next step.
C. Check the water pressure switch for faulty wiring and connections: Ensure
wire harness terminals are securely fastened to spade terminals on water
pressure switch. If OK, proceed to next step.
D. Verify the state of water pressure switch contacts: Remove wire leads from
water pressure switch and jumper leads. Then attempt to operate the heat-
er, measuring continuity across water pressure switch. If closed, LO code is
not caused by water pressure switch fault. If open, proceed to next step (af-
ter removing jumper from wire leads and reconnecting wire leads to water
pressure switch).
E. Ensure that low pump pressure does not exist. Clean filter or clear block-
ages. Check position of valves in plumbing system. If OK proceed to next
step.
F. Adjust water pressure switch setting as shown on page 33 of UHS Installa-
tion Manual (only if heater is above or below water level). If LO does not
clear, the water pressure switch is defective and must be replaced.
DIAGNOSTIC SEQUENCE (CONTINUED)
Possibility 2: Vent Pressure Switch Fault
(For UHS indoor installations only)
G. Check the vent pressure switch for faulty wiring and connections: En-
sure wire harness terminals are securely fastened to spade terminals on
vent pressure switch. If OK, proceed to next step.
H. Verify the state of vent pressure switch contacts: Remove wire leads from
vent pressure switch and jumper leads. Then attempt to operate the
heater, measuring continuity across vent pressure switch. If closed, LO
code is not caused by vent pressure switch fault. If open, proceed to next
step (after removing jumper from wire leads and reconnecting wire leads
to vent pressure switch).
I. Ensure that flue is not blocked or restricted: See indoor vent sizing re-
quirements in installation manual. If OK, the vent pressure switch is
defective and must be replaced.
Possibility 3: High Limit Switch Fault
J. Check the high limit switch for faulty wiring and connections: Ensure
wire harness terminals are securely fastened to spade terminals on high
limit switch. If OK, proceed to next step.
K. Verify the state of high limit switch contacts: Remove wire leads from
high limit switch and jumper leads. Then attempt to operate the heater,
measuring continuity across the high limit switch. If closed, LO code
is not caused by a high limit switch fault. If open, proceed to next step
(after removing jumper from wire leads and reconnecting wire leads to
high limit switch).
L. Verify that water flow rate to heater is above minimum required:
20 GPM for H150--- and H200---,
25 GPM for H250--- and H300---,
30 GPM for H350--- and H400---.
If OK, the high limit switch is defective and must be replaced.
Finally, remember that the problem could exist
in the wiring harness and also the control module.
FAULT CODE THUMBNAILS LO SWITCH OPEN WITHIN SAFETY LIMIT STRING (UHS, IDL2)
Heater System Solving Guide
FAULT CODE THUMBNAILS – PAGE F 14
FAULT CODE THUMBNAILS – PAGE F 14
Heater System Solving Guide
Fault Code Thumbnails LO Switch Open within Safety Limit String (IDL)
LO
SWITCH OPEN WITHIN SAFETY LIMIT STRING
IDL
PARTS THAT MAY BE NEEDED
• High Limit Switches • Control Module
• (Water) Pressure Switch • Wiring Harness
• Vent Pressure Switch
NOTE: “lo” is normal when pump is off. Otherwise, “lo” means a
control loop switch is open. Therefore, check for the following:
DIAGNOSTIC SEQUENCE
Possibility 1: Water Pressure Switch Fault
A. To verify that the pump is running, turn the pump OFF and watch to
see that the LO code clears. If LO does not clear, proceed to next step.
B. Verify that water flow rate to heater is above minimum required:
20 GPM for H150--- and H200---,
25 GPM for H250--- and H300---,
30 GPM for H350--- and H400---.
If OK, proceed to next step.
C. Check the water pressure switch for faulty wiring and connections:
Ensure wire harness terminals are securely fastened to spade terminals
on water pressure switch. If OK, proceed to next step.
D. Verify the state of water pressure switch contacts: Remove wire leads
from water pressure switch and jumper leads. Then attempt to oper-
ate the heater, measuring continuity across water pressure switch. If
closed, LO code is not caused by water pressure switch fault. If open,
proceed to next step (after removing jumper from wire leads and re-
connecting wire leads to water pressure switch).
E. Ensure that low pump pressure does not exist. Clean filter or clear
blockages. Check position of valves in plumbing system. If OK pro-
ceed to next step.
F. Adjust water pressure switch setting per instructions in IDL Installation
Manual (only if heater is above or below water level). If LO does not
clear, the water pressure switch is defective and must be replaced.
DIAGNOSTIC SEQUENCE (CONTINUED)
Possibility 2: Terminal Block Fault
G. Check if a remote on/off device connected to terminal block is open: Turn
remote device on, and watch for LO code to clear. If LO does not clear,
go to step I. If a remote on/off device is not connected to heater, go to step H.
H. Verify that jumper has been removed: If remote on/off control is not used, the
two far-right terminals of terminal block should be jumpered. If jumper is not
present. add jumper. Then, if LO code does not clear, proceed to next step.
I. Inspect terminal block wiring. Ensure wire harness terminals are securely
fastened to terminal block. If OK, terminal block is defective and should be
replaced.
Possibility 3: Vent Pressure Switch Fault
J. Check the vent pressure switch for faulty wiring and connections: Ensure wire
harness terminals are securely fastened to spade terminals on vent pressure
switch. If OK, proceed to next step.
K. Verify the state of vent pressure switch contacts: Remove wire leads from vent
pressure switch and jumper leads. Then attempt to operate the heater, mea-
suring continuity across vent pressure switch. If closed, LO code is not caused
by vent pressure switch fault. If open, proceed to next step (after removing
jumper from wire leads and reconnecting wire leads to vent pressure switch).
L. Ensure that flue is not blocked or restricted: See indoor vent sizing require-
ments in installation manual. If OK, the vent pressure switch is defective and
must be replaced.
Possibility 4: Temperature Limit Switch Fault
M. Check the high limit switch for faulty wiring and connections: Ensure
wire harness terminals are securely fastened to spade terminals on high
limit switch. If OK, proceed to next step.
N. Verify the state of high limit switch contacts: Remove wire leads from
high limit switch and jumper leads. Then attempt to operate the heater,
measuring continuity across the high limit switch. If closed, LO code
is not caused by a high limit switch fault. If open, proceed to next step
(after removing jumper from wire leads and reconnecting wire leads to
high limit switch).
O. Verify that water flow rate to heater is above minimum required:
20 GPM for H150--- and H200---,
25 GPM for H250--- and H300---,
30 GPM for H350--- and H400---.
If OK, the high limit switch is defective and must be replaced.
Finally, remember that the problem could exist
in the wiring harness and also the control module.
FAULT CODE THUMBNAILS LO SWITCH OPEN WITHIN SAFETY LIMIT STRING (IDL)
FAULT CODE THUMBNAILS – PAGE F 15
FAULT CODE THUMBNAILS – PAGE F 15
Heater System Solving Guide
Fault Code Thumbnails LO Switch Open within Safety Limit String (ED2)
LO
SWITCH OPEN WITHIN SAFETY LIMIT STRING
ED2
PARTS THAT MAY BE NEEDED
• High Limit Switches • Control Module
• (Water) Pressure Switch • Wiring Harness
• Vent Pressure Switch
NOTE: “lo” is normal when pump is off. Otherwise, “lo” means a
control loop switch is open. Therefore, check for the following:
DIAGNOSTIC SEQUENCE
Possibility 1: Water Pressure Switch Fault
A. To verify that the pump is running, turn the pump OFF and watch to
see that the LO code clears. If LO does not clear, proceed to next step.
B. Check the water pressure switch for faulty wiring and connections:
Ensure wire harness terminals are securely fastened to spade terminals
on water pressure switch. If OK, proceed to next step.
C. Verify the state of water pressure switch contacts: Remove wire leads
from water pressure switch and jumper leads. Then attempt to oper-
ate the heater, measuring continuity across water pressure switch. If
closed, LO code is not caused by water pressure switch fault. If open,
proceed to next step (after removing jumper from wire leads and re-
connecting wire leads to water pressure switch).
D. Ensure that low pump pressure does not exist. Clean filter or clear
blockages. Check position of valves in plumbing system. If OK pro-
ceed to next step.
E. Adjust water pressure switch setting per instructions in IDL Installation
Manual (only if heater is above or below water level). If LO does not
clear, the water pressure switch is defective and must be replaced.
DIAGNOSTIC SEQUENCE (CONTINUED)
Possibility 2: Automatic Temperature Limit Switch Fault
F. Check the (automatic) temperature limit switch for faulty wiring and connections:
Ensure wire harness terminals are securely fastened to spade terminals on the
temp limit switch. If OK, proceed to next step.
G. Verify the state of (automatic) temperature limit switch contacts: Remove wire
leads from (automatic) temp limit switch and jumper the leads. Then attempt to
operate the heater, measuring continuity across (automatic) temp limit switch.
If closed, LO code is not caused by (automatic) temperature limit switch fault.
If open, proceed to next step.
H. OUTDOOR UNITS ONLY: Check for high winds or severe downdrafting and, if
necessary, install High Wind Stack. (For indoor units, skip ahead to next step.)
I. Ensure that flue is not blocked or restricted: Refer to vent sizing requirements.
J. Check for sooted or damaged exchanger. If sooted or damaged, the exchanger
should be cleaned (and may need to be replaced).
Possibility 3: Manual Temperature Limit Switch Fault
K. Repeat steps F through J for manual temperature limit switch.
L. Reset manual temperature limit switch. If switch continues to trip, replace the
manual temperature limit switch.
Possibility 4: High Limit Switch Fault
M. Check the high limit switch for faulty wiring or connections. Ensure wire harness
terminals are securely fastened to spade terminals.
N. Verify state of high limit contacts. Remove wire leads from high limit switches
and jumper leads. Operate heater, and measure continuity across high limit
switches. If closed, LO code is not caused by high limit switch fault. If open, re-
move jumper from leads, reconnect leads to high limit switches, and proceed to
next step.
Possibility 5: Inadequater Water Flow Fault
Q. Verify that water flow rate to heater is above minimum required: 25 GPM.
R. At this point, it must be assumed that a high limit switch is faulty and must be
replaced.
FAULT CODE THUMBNAILS LO SWITCH OPEN WITHIN SAFETY LIMIT STRING (ED2)
Heater System Solving Guide
FAULT CODE THUMBNAILS – PAGE F 16
FAULT CODE THUMBNAILS – PAGE F 16
Heater System Solving Guide
Fault Code Thumbnails SB Keypad Failure
FAULT CODE THUMBNAILS SB KEYPAD FAILURE
UHS IDL2
SB
KEYPAD FAILURE
PARTS THAT MAY BE NEEDED
• Keypad/Membrane Switch
DIAGNOSTIC SEQUENCE
A. Replace keypad/membrane switch.
FAULT CODE THUMBNAILS – PAGE F 17
FAULT CODE THUMBNAILS – PAGE F 17
Heater System Solving Guide
Fault Code Thumbnails SF Temperature Sensor Input Failure
FAULT CODE THUMBNAILS SF TEMPERATURE SENSOR INPUT FAILURE
IDL
UHS
IDL2
ED2
SF
TEMPERATURE SENSOR INPUT FAILURE
PARTS THAT MAY BE NEEDED
• Thermistor
• Control Module
DIAGNOSTIC SEQUENCE
A. Check where the thermistor connects
to the board to see if it has become disconnected or damaged.
B. Replace thermistor if wire or connection is damaged.
C. Replace control module if connection on board is damaged
D. Replace control module if new thermistor does not correct fault.
Heater System Solving Guide
FAULT CODE THUMBNAILS – PAGE F 18
FAULT CODE THUMBNAILS – PAGE F 18
Heater System Solving Guide
Fault Code Thumbnails Fault Conditions with NO CODE
FAULT CODE THUMBNAILS FAULT CONDITIONS WITH NO CODE
FAULT CONDITIONS WITH NO CODE
UHS, IDL2
PARTS THAT MAY BE NEEDED
• Fuses (FC1, FC2, FC3, FC4) • Transformer
• Fuse Board • Control Module
• Wiring • Wiring Harness
DIAGNOSTIC SEQUENCE
Heater Will Not Power Up
A. Verify that low & high voltage is being output from fuse board:
Disconnect the P5 connector from fuse board plug, and measure for
24vac between pins on fuse board receptacle. Reconnect the P5 plug, and
disconnect P6 connector plug on the fuse board. Measure for 120VAC
between pin 3 and 6 of receptacle on fuse board.
If OK, reconnect P6 plug and proceed to next fault condition, Low
Voltage Circuit Fault.
Otherwise, reconnect P6 plug and proceed to step B.
B. Verify heater is getting field power by measuring for field supply voltage
across terminals of TB1 terminal block on fuse board.
C. Inspect fuse board wiring, and ensure all plugs are securely fastened to
fuse board.
D. Remove FC1 and FC2 fuses from fuseholder. Measure continuity across
fuse.
If fuses are open, proceed to fault condition Open Fuse: FC2 or F1.
If fuses are OK, reinstall them and proceed to step E.
E. Check that the proper voltage selector plug is installed in fuse board.
F. Disconnect P4 connector from fuse board plug. Measure for 24VAC
between pins 1 & 2 of plug of transformer and for 120VAC between pins
4 & 6.
If 24VAC or 120VAC is not present, replace transformer.
Otherwise, replace fuse board.
Low Voltage Circuit Fault
G. Disconnect P5 connector from fuse board plug. Measure for 24VAC
across pins. Reconnect plug.
If OK, proceed to step H. Otherwise proceed to step K.
H. Inspect control module wiring. Ensure all plugs are securely fastened to
control module.
I. Verify 24VAC across R and C terminals on control module.
If not OK, replace harness.
J. Remove F1 fuse from fuseholder. Measure continuity across fuse.
If OK, replace control module.
If fuse is open, proceed to fault condition Open Fuse: FC3 or F1.
K. Remove FC3 fuse from fuseholder. Measure continuity across fuse.
If fuse is open, proceed to fault condition Open Fuse: FC3 or F1.
If OK, reinstall fuse and proceed to step L.
L. Disconnect P4 connector from fuse board plug. Measure for 24VAC
between pins 1 & 2 of plug from transformer. If 24VAC is not present,
replace the transformer. Otherwise, replace fuse board.
Open Fuse: FC2 or FC1
M. Check that proper voltage selector plug is installed.
N. If 120VAC plug is installed but field supply voltage is 240VAC, FC1 and
FC2 fuses will have opened. Install the correct voltage selector plug
(240VAC) and new FC1 and FC2 fuses.
O. Inspect transformer wiring. Ensure insulation on wiring is not worn.
If OK, replace the transformer.
Open Fuse: FC3 or FC1
P. Inspect gas valve wiring. Ensure insulation on wiring is not worn.
Q. Measure for resistance across gas valve terminals and between each ter-
minal and ground. If short exists, replace gas valve.
R. Inspect control module wiring. Ensure insulation on wiring is not worn.
If OK, replace the control module.
Open Fuse: FC4
S. Inspect ignitor wiring. Ensure insulation on wiring is not worn.
T. Inspect blower wiring. Ensure insulation on wiring is not worn.
U. Disconnect ignitor plug from control module. Measure resistance across
Igniter. If shorted, replace ignitor.
V. Disconnect blower plug from control module. Measure resistance across
blower windings. Winding resistance across lead should be in the following
range:
IDL2: Black to White 10-14 ohms Red to White 18-22 ohms
UHS: Red to White 8-9 ohms
If measured values vary substantially from these values, blower is defective
and must be replaced. Otherwise, replace the control module.
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