DCG31 & DCG32 SERIES
COMMERCIAL GAS DAMPERED WATER HEATERS
Check for 24V
between black
and white wires
on ignition
control
module
YES
When
thermostat NO
turned up, does
pilot spark?
YES
YES
Check for
24V between
PV & PV/MV
terminals on
gas valve
NO
Does sparking
stop?
YES
Replace
gas
valve
NO
Replace
ignition
control
Replace
ignition
control
module
Check for 24V
between PV
and PV/MV
terminals on
ignition control
module
Check for
24V between
yellow and
white wires
on damper
harness
YES
Check spark
wire for damage
& continuity.
Also check
spark assembly
FOUND
ALL
for cracks in
DAMAGE
OKAY
ceramic or
wrong spark
gap
Clean flame
sensor - check
ground. If still
problem,
see below
Problem is
either bad
spark assembly
or wiring
between spark
assembly and
control
module
Replace
lower
sensor/
ECO
YES
NO
NO
Check for
24V between
PV & MV/PV
terminals on
ignition
control
module
NO
YES
Replace
faulty
component
Does main
burner fire?
NO
YES
Is there 24V
between MV
& MV/PV
terminals at
gas valve?
Go to
NO
thermostat
troubleshooting
chart
FC31/32-0805
YES
Does main
burner stay
lit until
thermostat
satisfies?
NO
Does pilot
light shrink
or go out
when main
burner fires?
YES
Is gas flex
being used,
or other
small gas
pipe?
Check for
blockage in
burner or
orifice, also
check
incoming
gas supply
NO
Bypass
damper, if
heater fires
then
replace
damper
Go to
thermostat
troubleshooting
flow chart
Replace
ignition
control
Is there 24V
between MV
& MV/PV
terminals at
ignition
control
module?
NO
YES
ALL
SHOULD
BE
OKAY
NO
Repair
ground
Does
pilot ignite?
YES
NO
Is ground
good from
control
module to
incoming
ground?
NO
YES
OK
Replace
gas
valve
Check &
adjust gas
pressure
OK
Copyright© by American Water Heater Company 2005. All rights reserved.
Replace
ignition
control
module
YES
DCG31 & DCG32 SERIES
COMMERCIAL GAS DAMPERED WATER HEATER THERMOSTAT
No voltage or
low voltage
from yellow
wire between
thermostat
board & damper
Replace
bad
sensor
With an ohm
meter set at X1,
check orange
NO wires on set pot
(6,000 ohms at
lowest setting
& 0 ohms at
highest setting
Replace
set pot
Ohm
reading
no good
OK
Has bad spot
When slowly
turning set pot
dial from low to
high, ohm
reading should
be a smooth
transition with
no skips, jumps
or glitches
OK
Take ohm reading
from upper sensor
and lower sensor
and compare
reading with chart
on next page (A
termperature reading
from a water sample
taken from the T&P
valve is also needed
for this test)
Ohms
show
OK
Replace
thermostat
circuit
board
Sequence of Operation:
When thermostat contacts close on a call for heat, a 24 Volt signal is sent to the damper and
cause it to open. When the damper proves fully open, the 24 Volt signal continues to the
ignition control module will then start sparking at the pilot head while at the same time
sending 24 volts to the pilot valve portion of the gas valve to open it and allow the main
burner to light. The main burner will continue to fire until the thermostat system is satisfied
and opens the thermostat contacts, causing the damper to close and the ignition control
module to shut down.
FC31/32-0805
Copyright© by American Water Heater Company 2005. All rights reserved.