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26
Heater Will Not Fire - C
Start
Go to “INITIAL
TROUBLESHOOTING”
Continue to observe heater
for several minutes. Cycle
heater on and off several
times. Observe for delayed or
rough ignition, poor combus-
tion, premature extinction of
flame, evidence of boiling, or
operation of any diagnostic
LED. Go to pertinent trou-
bleshooting section if any
malfunction is observed.
Replace Control Board.
Replace Gas Valve with
identical part.
Fix wiring between TH and
GND terminals of Ignition
Control Module and Control
Board.
Replace Control Board.
Fix wiring between GAS ter-
minals on Control Board and
Gas Valve.
NOTE 1: Voltage appears about 24
seconds after call for heat, and may
be on for only about 7 seconds.
NOTE 2: Voltage appears immedi-
ately after call for heat, and may be
on for only about 30 seconds.
Verify that gas supply is open
all the way to Gas Valve, and
Gas Valve knob is at “on”
position.
Check for 24 VAC to Gas
Valve terminals during ignition
try. (Voltage appears about 24
seconds after call for heat).
SEE NOTE 1.
Turn off 120 VAC
power to heater for 5
seconds, and turn
back on.
Make sure tempera-
ture setting is above
water temperature.
Wait one minute.
Does heater fire and
stay on?
Did Blower come on?
Verify that gas is flow-
ing to burner during
ignition try. Observe
gas meter for move-
ment during ignition
try (wait for about 30
seconds after calling
for heat).
Check for 24 VAC
between TH and GND
terminals on Ignition
Control Module.
SEE NOTE 2.
Check for 24 VAC
between TH and GND
terminals on Control
Board. SEE NOTE 2.
Check for 24 VAC
between GAS termi-
nals on Control
Board. SEE NOTE 1.
Replace Control
Board.
NO
CONTINUE
YES
YES
YES
NO
NO
YES
NO
YES
NO
NO
YES
YES
NO
YES
YES
Is “SERVICE HEATER” LED
“on”?
Go to “BURNER
TROUBLESHOOTING”
(Page 30)
Go to “HEATER WILL NOT
FIRE-D” (Page 27)
Check for 24 VAC between
VAL and GND terminals on
Ignition Control Module.
SEE NOTE 1.
Check for 24 VAC between
VAL and GND terminals on
Control Board. SEE NOTE 1.
If any red diagnostic LED’s
(AGS, AFS, SFS, HLS, PS, or
THERMISTOR) come “on”, go
to Pages 28 and 29.
Did burner fire at all?
Replace Ignition Control
Module.
NO
YES
Fix wiring between VAL and
GND terminals of Ignition
Control Module and Control
Board.
NO
YES
NO
NO