42
SERVICING
Service Problem No Heat Unsatisfactory Heat
POSSIBLE CAUSE
DOTS IN ANALYSIS
GUIDE INDICATE
"POSSIBLE CAUSE"
SYMPTOM
System Will Not Start
Burner Won't Ignite
Burner Ignites-Locks Out
Burner Shuts Off prior to T'Stat being Satisfied
Short Cycles
Long Cycles
Soot and /or Fumes
Too Much Heat
Not Enough Heat
Test Method
Remedy
See Service Procedure Reference
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)
••
Test Blower Motor (PSC)
S-16A
Broken or Shorted Ignitor
•
Test Ignit or
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