Troubleshooting flowchart – John Wood Commercial - AJWS User Manual
Page 22
TROUBLESHOOTING FLOWCHART
22
High water temp.
Will ECO light
reset once temp.
in t
ank cools?
Check continuity
across ECO.
Replace
ECO.
No hot water
.
Power to heater?
Is ECO light “ON”?
Go to next p
age.
Rep
air
power
problem.
When thermost
at
is turned up does
pilot sp
ark?
Check for 24V
between purple &
white wires on the
ignition control
module (ICM).
Is ground good
from ICM to
incoming ground?
Check for 24V
between PV &
PV/MV terminals
on gas valve.
Does pilot light?
Rep
air
ground.
Replace
gas valve.
Does sp
arking
stop?
Check for 24V
between PV
&
MV/PV terminals
on ICM
Check for 24V
between orange &
white wires on
damper harness.
Check for 24V
between PV
&
MV/PV terminals
on ICM.
Clean flame
sensor - check
ground.
Replace
ICM.
Check sp
ark wire
for damage & con-
tinuity
. Check
sp
ark ass’y for
cracks in ceramic
or wrong gap.
Byp
ass
damper
,
orange & purple
wires. If heater
fires, then replace
damper
.
Replace
ICM.
Bad
sp
ark ass’y
or wiring
between sp
ark
ass’y and
ICM.
Replace
faulty
p
art
s.
Replace
ICM
Go to next p
age.
Check gas supply
.
Rep
air
gas supply
.
All should
be OK.
Is there 24V
between MV &
MV/PV terminals
at the ICM?
Does main burner
st
ay lit until ther-
most
at satisfies?
Check for block-
age in burner or
orifice. Also
check
incoming gas sup-
ply
.
Does main burner
fire?
Is there 24V
between PV &
PV/MV terminals
at gas valve?
Replace
ICM.
Replace
gas valve.
Check and
adjust gas
pressure.
Go to next p
age.
Does pilot light
shrink or go out
when main burner
fires?
Is gas flex being
used, or other
small gas pipe?
Open
Closed
All OK
Found
damage
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
OK
Y
Y
Y
Y
OK
OK
N