SERVICING
53
Service Problem
No Heat
Unsatisfactory Heat
POSSIBLE CAUSE
DOTS IN ANALYSIS
GUIDE INDICATE
"POSSIBLE CAUSE"
SY
M
P
TO
M
S
ys
te
m
W
ill
N
ot S
ta
rt
B
ur
ner
Won
't Ig
ni
te
B
ur
ne
r I
gn
ite
s-
Lo
cks Ou
t
Bu
rn
er
Sh
ut
s O
ff
p
rio
r t
o
T'
Sta
t
be
in
g Sa
tis
fie
d
S
hor
t C
ycle
s
Lon
g C
yc
le
s
So
ot
a
nd /
or
Fum
e
s
T
oo M
uc
h H
e
at
N
ot En
ou
gh
H
e
at
Test Method
Remedy
Se
e Se
rv
ic
e Pro
ce
d
u
re
Re
fe
re
n
ce
Power Failure
•
Test Voltage
S-1
Blown Fuse
•
Test Voltage
S-4
Loose Connection
•
Check Wiring
S-2
Shorted or Broken Wires
•
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 Ground 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 & ECM)
•
•
Test Blower Motor (PSC & ECM)
S-16A,B,C
Broken or Shorted Ignitor
•
Test Ignitor
S-308
Dirty Flame Sensor, Low UA
•
Clean Flame Sensor
S-314
Stuck Gas Valve
•
• •
Replace Gas Valve
S-304
Faulty Gas Valve
•
•
•
Replace Gas Valve
S-304
Open Auxiliary Limit
•
•
Reset Control
S-301
Improper Air Flow or Distribution
•
•
Check Duct Static
S-200
Cycling on Limit
• •
•
Check Controls & Temperature Rise
S-201 / S-300
Delayed Ignition
•
Test for Delayed Ignition
S-312
Flashback
•
Test for Flashback
S-309 / S-311
Orifice Size
• • •
Check Orifices
S-306 / S-311
Gas Pressure
•
• • •
Check Gas Pressure
S-307
Cracked Heat Exchanger
•
Check Burner Flames
S-305
Furnace Undersized
•
•
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 Switch
• •
Test Flame Roll Out Control
S-302
Bouncing On Pressure Switch
•
Test Negative Pressure
S-310
