20
Ye
s
Fan
Mo
to
r
Runs
, Igniter
Sparks,
Heater
Does
no
t
Light.
Is v
oltage
supplied t
o
transf
ormer when ignit
er
sparks?
Ye
s
No
Ye
s
Check all wiring connections. If good, replace ignition contr
ol
No
Is
gas contr
ol v
alv
e
set t
o ON
position?
Clean the orif
ice
Are 2
4 v
olts
supplied fr
om
transf
ormer?
Ye
s
R
eplace
transf
ormer
No
Is
contr
ol v
alv
e
receiving 2
4 v
olts
fr
om limit
switch(es)?
Ye
s
No
Set the contr
ol
valv
e t
o ON.
No
Is gas
contr
ol v
alv
e
receiving pr
oper inlet
gas supply pressure?
Pr
ovide pr
oper Inlet
pressure. R
ef
er t
o
heat
er’s dataplat
e.
Ye
s
No
Are fuel supply v
alv
es open?
Open all fuel supply
valv
es t
o heat
er
.
Ye
s
Is
burner orif
ice
plugged with dust/dir
t?
Ye
s
No
Check f
or manif
old pressure. If no
pressure, the contr
ol v
alv
e is def
ectiv
e.
R
eplace contr
ol v
alv
e.
Problem
Def
ectiv
e high limit
switch. R
eplace the
limit switch.
Ye
s
Are
high limit switch contacts open? Check continuity
No
R
eset the limit switch.
(Press the rest butt
on)
R
echeck f
or continuity
.
Det
ermine cause of limit
tripping. Check f
or
obstructions in air inlet or discharge, ensure heat
er is
clean, remo
ve kinks fr
om
duct if duct is used.
R
epair or replace
electrical connections or
wiring.
Are
electrical wires and
connections fr
om limit
switch t
o contr
ol v
alv
e
in good condition?
Ye
s
No