SERVICE AND TECHNICAL SUPPORT MANUAL
Gas Furnace: N9MSB
Specifications subject to change without notice.
26
440 04 4413 03
Figure 16
Troubleshooting Guide
−
Flow Chart
Is
LE
D s
tat
us lig
ht
ON s
oli
d,
alt
ern
atel
y
flashi
ng bri
ght
-d
im
-b
rig
ht-
dim
lik
e a
hea
rtb
ea
t, o
r fl
ashi
ng
ON a
nd
O
F
F
?
Is
th
er
e 2
4V a
t
2
4VAC a
nd
C
O
M
?
Is
th
er
e 1
15V
at
L1
an
d
NE
UT
RA
L?
Is
th
e 2
4V
f
use
op
en
?
Is
do
or
s
w
itc
h clo
sed
?
Rep
la
ce t
ra
nsf
orm
er
.
Rep
la
ce do
or
sw
itch
.
Is
th
er
e 1
15V
goi
ng t
o s
w
itch
?
Cl
ose
the
d
oor
s
w
itc
h.
Is
circ
uit
bre
ak
er cl
ose
d?
Che
ck
fo
r co
nti
nuit
y i
n
w
ir
e
fr
om
ci
rc
ui
t
br
ea
ke
r to
fu
rn
ac
e.
Cl
ose
circ
uit b
re
ak
er a
nd
go
ba
ck
to
ST
ART
.
Is
LE
D s
tat
us li
g
ht
alte
rn
atel
y fla
shin
g
brig
ht
-d
im
-b
rig
ht-
dim
lik
e a h
ea
rtb
eat
?
Dete
rm
ine
s
ta
tus c
od
e. T
h
e st
atu
s co
d
e
is a
si
ngle
or
t
w
o
di
git
n
um
be
r
w
ith
t
he
fir
st
num
b
er
det
erm
in
ed b
y
the num
b
er of
shor
t fl
ash
es a
nd
th
e se
con
d
num
be
r
afte
r
the plus (+)
sig
n,
t
he num
b
er
of l
o
ng
flash
es.
T
o r
ec
all a
sta
tu
s
cod
e: B
riefl
y
(2
–
3
seco
nds
) c
onn
ect
th
e
T
EST
/T
W
IN te
rm
ina
l
to t
he
“C”
the
rm
ost
at t
erm
in
al
w
ith
a j
u
m
per
wi
re
t
o b
egi
n st
atu
s co
de
re
cov
er
y
an
d
com
po
nen
t t
est.
If a
pr
evio
us s
tat
us c
o
de is
pres
en
t, t
he c
od
e
w
ill
re
pea
t 4
tim
es t
h
en
go
on t
o c
om
po
nen
t t
est.
If n
o
pre
viou
s
cod
e is p
re
sen
t, a
com
p
on
ent
tes
t
w
ill
begi
n w
ith
o
ut
flashi
ng an
y sta
tus cod
es
.
C
o
mpon
en
t T
e
st
S
equ
enc
e
: Ga
s
va
lv
e
and
hum
idi
fier
w
ill
n
ot
be t
ur
ne
d
on
.
In
d
uce
r
m
oto
r w
ill sta
rt
a
nd
r
em
ai
n on until
the
en
d o
f th
e bl
o
w
e
r t
est,
th
en
off.
T
he
fo
llow
in
g co
mp
on
en
ts
a
re
on
fo
r
10
–
15
seco
nds
ea
ch i
ndivi
duall
y: h
ot s
ur
fac
e
ign
ite
r,
blo
wer spe
eds
: FA
N
(if
pr
es
ent
),
HE
AT
, COOL
.
W
as there
a p
revi
ous
stat
us c
od
e
?
Go t
o s
ectio
n b
elo
w fo
r t
he fl
ash
ed
sta
tus
cod
e.
Doe
s
th
e
co
ntr
ol r
esp
on
d t
o
W
, Y
1,
Y
/Y2,
and
G
(24V
) t
he
rm
osta
t sig
nals
?
Run s
ystem
t
hr
ou
gh
a
h
eat
, o
r c
ooli
n
g
cy
cle t
o c
heck
op
er
atio
n. S
tat
us c
od
es
are
er
ase
d
afte
r 7
2
hou
rs.
Is
2
4V
p
res
ent
at
W
, Y
1,
Y/
Y
2
or
G
the
rm
osta
t te
rm
inals
o
n th
e f
ur
nac
e
cont
rol
?
Check
ro
om
th
erm
os
tat
or
in
te
rc
o
nn
ec
ting
c
a
bl
e.
Di
scon
nec
t all
the
th
erm
os
tat
wi
re
s fr
o
m
the fur
nac
e
cont
rol.
Does
the
p
robl
em
r
epe
at
whe
n u
sing
a
jum
per
w
ire
?
Repla
ce f
ur
nac
e c
ont
rol.
T
he th
erm
os
tat
is n
ot c
om
pati
ble
w
ith
th
e
fur
nac
e co
ntr
ol.
E
ithe
r i
nstall
a
ball
a
st
resist
or,
co
nn
ect t
he
C
fu
rn
ace
co
ntr
ol
th
e
rm
osta
t te
rm
ina
l to
th
e
th
er
m
os
ta
t,
o
r
repl
ace
th
e t
herm
o
stat
.
YE
S
NO
YE
S
YE
S
YE
S
YE
S
YE
S
YE
S
YE
S
STAR
T
YE
S
YE
S
NO
NO
NO
NO
NO
NO
NO
NO
YE
S
NO
NO
Troubles
h
ooting Guide
Repla
ce f
ur
nac
e c
ont
rol.
YE
S
Insp
ect
se
cond
ar
y volt
ag
e
(2
4V
) w
iri
ng,
includi
ng
th
erm
ost
at l
ea
ds f
or s
ho
rt
circuit
.
Rep
la
ce f
us
e
NO
Is
L
E
D s
ta
tus lig
ht
ON s
olid?
NO
YE
S
T
he co
ntr
ol is l
ock
ed
out
an
d
w
ill
aut
o
-
rese
t a
fte
r
1 ho
ur.
L
ock
out coul
d be du
e
to
a
n
y of
the fo
llo
w
in
g
:
-
Flam
e s
en
se ci
rcui
t fail
ur
e.
-
G
as
va
lv
e r
elay
st
uc
k op
en
.
- S
of
tw
a
re
che
ck
err
or.
Rese
t p
o
wer
to
cle
ar l
ock
out.
Re
plac
e
cont
rol if
co
de
re
pe
ats.
