Filter
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28
Diagnostic LED’s: AGS, AFS, HLS, PS, THERMISTOR
Do not jumper a safety switch to
remedy a failed switch.
NOTE: ES1 is a spare and should be jumpered.
CAUTIO
N
Service pump and filter to
restore proper flow. After ser-
vicing, verify proper operation
of Pressure Switch (PS).
Replace thermistor or Control
Board to correct overheating.
Replace High Limit
Switch (HLS) or
Automatic Gas
Shutoff (AGS)
If problem persists, verify proper operation of Internal Bypass Valve
and Thermal Governor, and check for Heat Exchanger blockage.
YES
NO
NO
AGS or HLS “on”
Verify that water flow rate is
above minimum required for
heater.
Verify that inlet water temper-
ature is below 104° F.
YES
CONTINUE
YES
CONTINUE
Verify that there is no block-
age in Blower intake, Heat
Exchanger, and exhaust and
that exhaust is not too long
(see “Indoor Vent Installation”,
Page 15.
Verify correct connection of
wiring and that pressure taps
to AFS are OK.
Verify that vinyl tubing to AFS
and Blower is not misrouted,
kinked, disconnected, or
punctured.
Replace Air Flow Switch
(AFS).
If problem persists, replace
Blower.
Replace Blower.
Verify correct
connection of wiring between
24 VAC and IND terminals on
Ignition Control Module and
Control Board, and replace
Control Board.
YES
YES
NO
NO
NO
YES
YES
NO
AFS “on”
Does Blower operate?
THERMISTOR “on”
Verify Thermistor wiring. If
OK, replace Thermistor.
Disconnect Blower and check
for line voltage between pins
1 and 3 of Blower Connector
on ignition try.
Connect correctly and retry.
Does Blower start?
Replace Blower. Does Blower
start on ignition try?
Replace Ignition Control
Module.
NO
Verify that wires BM
and F1 are correctly
connected at the
terminal strip (see
Heater Connection
Diagram, Page 36).
Disconnect wires F1
and F2 from Ignition
Control Module and
short them together.
Does Blower come
on?
Check for 24 VAC between
24 VAC and GND terminals
on Ignition Control Module on
ignition try. Check that IND
wire is correctly connected.
NO
NO
Service pump and filter to
restore proper flow.
Verify that wiring is
OK and pressure tap
is not blocked. Re-
place Pressure Switch
CONTINUE
NO
PS “on”
Verify that water flow rate is
above minimum required for
heater.
Adjust Water Pressure Switch to close with pump running and open with
pump off.
YES