SERVICING
41
Service Problem
No Heat
Unsatisfactory Heat
POSSIBLE CAUSE
DOTS IN ANALYSIS
GUIDE INDICATE
"POSSIBLE CAUSE"
SY
M
P
T
O
M
S
yst
em
W
il
l N
o
t
S
ta
rt
B
ur
n
er
W
o
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't I
g
n
ite
B
u
rn
e
r Ig
ni
te
s-
L
o
ck
s O
u
t
B
u
rn
er
S
hut
s
O
ff
pr
io
r
to
T'
S
ta
t be
ing
S
a
tis
fi
ed
S
h
o
rt
C
y
cl
es
Lo
ng C
yc
le
s
S
oot
a
nd /
o
r Fu
m
es
Too M
uc
h
H
e
at
N
o
t E
nough
H
ea
t
Test Method
Remedy
S
ee S
e
rv
ice P
ro
ced
u
re
Ref
e
re
n
c
e
Power Failure
•
Test Voltage
S-1
Blown Fuse
•
Test Voltage
S-4
Loose Connection
•
Check Wiring
S-2
Shorted or Broken Wi res
•
Check Wiring
S-3A
No Low Voltage
•
Check Transformer
S-4
Faulty Thermostat
•
• •
• •
Check Thermostat
S-3A
Faulty Transformer
•
Check Transformer
S-4
Poor or High Resistance Ground
•
Measure Gr ound Resistance
S-17B
Improper Heat Anticipator Setting
• •
• •
Adjust Heat Anticipator Setting
S-3B
Improper Thermostat Location
• •
• •
Relocate Thermostat
S-316
Faulty Limit or Roll Out Switch
•
•
Test Control
S-300 / S-302
Faulty Flame Sensor
•
Test Flame Sensor
S-314
Faulty Ignition Control
• • •
Test Control
S-313
Gas Valve or Gas Supply Shut Off
•
Turn Valves to On Position
S-317
Faulty Induced Draft Blower
•
•
Test Induced Draft Motor
S-303
Faulty Blower Motor (PSC)
•
•
Test Blower Motor (PSC)
S-16A,B,C
Broken or Shorted Ignitor
•
Test Ignitor
S-308
Di rty Flame Sensor, Low UA
•
Clean Flame Sensor
S-314
Stuck Gas Val ve
•
• •
Replace Gas Valve
S-304
Faulty Gas Val ve
•
•
•
Replace Gas Valve
S-304
Open Auxil iary Limit
•
•
Reset Control
S-301
Improper Air Flow or Distribution
•
•
Check Duct Static
S-200
Cycling on Li mit
• •
•
Check Controls & Temperature Rise
S-201 / S-300
Delayed Ignition
•
Test for Del ayed Igni tion
S-312
Fl ashback
•
Test for Flashback
S-309 / S-311
Orifice Si ze
• • •
Check Orifi ces
S-306 / S-311
Gas Pressure
•
• • •
Check Gas Pressure
S-307
Cracked Heat Exchanger
•
Check Burner Flames
S-305
Furnace Undersi zed
•
•
Replace with Proper Size Furnace
S-318
Furnace Oversized
•
Replace with Proper Size Furnace
S-318
Faulty Pressure Switch
• • •
Test Pressure Switch
S-310
Blocked or Restricted Flue
•
Check Flue/Drawdown Pressure
S-310
Open Roll Out Swi tch
• •
Test Flame Roll Out Control
S-302
Bouncing On Pressure Swi tch
•
Test Negative Pressure
S-310
