43
Page
Display
Green
LED
Malfunction
descrip
tion
Diagnosis
391
Two Times
Air-fuel ra
tio
rod
failure
•
Check for c
onnection/b
reakage of wires (Part #708)
and
/
or soot on the AFR rod (Part #108).
510
Six Times
Abnormal
main gas
solenoid valve
•
Check for connec
tion/b
reakage of wires (Part #707)
and
/
or
bu
rn marks on the computer
bo
ard (Part #701).
•
Check for signs of vent corrosion.
•
Check gas valve contacts and gas valve wire harness
connec
tions
for signs of rust or corrosion.
551
Six Times
Abnormal
gas
solenoid valve
•
Check for connec
tion/b
reakage of wires (Part #707)
and
/
or
bu
rn marks on the computer
bo
ard (Part #701).
•
Check gas valve contacts and gas valve wire harness
connec
tions
for signs of rust or corrosion..
611
Four Times Fan motor fault
•
Check for c
onnection/b
reakage of wires, dust
buildup
in the fan motor (Part #103) and
/
or
burn
marks on
the computer
boa
rd (Part #701).
•
Check for frozen
/
corrosion of connectors (Part #103).
701
One Time
Computer
boa
rd fault
•
Check for c
onnection/b
reakage of wires (Part #711).
711
One Time
Gas solenoid valve
drive circuit failure
•
Refer to the 111 and 121 error codes.
721
Six Times
False
flame
det
ection
•
Check if there is leaking from heat exchanger (Part #401).
751
N
/
A
Miscommunica
tion
b
etween
micro-boiler
and temperature
controller
•
Inspect the c
onnections
b
etween the
micro-boiler
and temperature controller.
•
Check the power supply of the
micro-boiler.
941
Five Times
Abnormal
exhaust
temperature
•
Check to see of the exhaust temperature is higher
than 149°F (65°C).
991
Five Times
Imperfect
c
ombu
s
tion
•
Check if the gas type of the
micro-boiler
matches
the gas supplied to it.
•
Inspect the environment around the
micro-boiler.
Determine how long the
micro-boiler
has
been
installed and match DIPswitches.
•
Check the
altitude/
eleva
tion
of the area of where
the
micro-boiler
is installed.
•
Check if there is any
bloc
kage in the intake air
and/
or exhaust.
•
If the
micro-boiler
is installed as a direct-vent
system, check whether there is enough distance
b
etween the intake air terminal and the exhaust
terminal.
•
Check if there is grease and
/
or dirt in the
bu
rner (Part
#101) and the fan motor (Part #103), especially if the
micro-boiler
has
b
een installed in a contaminated area
•
Check the DIPswitches match gas type of the
micro-boiler.
•
Check the manifold pressure at Max. and Min.
•
Check com
bu
s
tion
cham
b
er t
ub
e (part #117) to see if it
is clear and securely installed.
Owner's Guide
Summary of Contents for HS120CON-LP
Page 27: ......
