SERVICING
57
Rev. 0
Complaint
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
bein
g
Satisfied
Short Cycles
Long Cycles
Soot and /or Fumes
To 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-3
No Low Voltage
•
Check Transformer
S-4
Faulty Thermostat
•
•
•
•
Check Thermostat
S-3
Faulty Transformer
•
Check Transformer
S-4
Poor or High Resistance Ground
•
Measure Ground Resistance
S-21
Improper Heat Anticipator Setting
•
•
•
•
Adjust Heat Anticipator Setting
S-3
Improper Thermostat Location
•
•
•
•
Relocate Thermostat
Faulty Limit or Roll Out Switch
•
•
Test Control
S-5 & 22
Faulty Flame Sensor
•
Test Flame Sensor
S-21
Faulty Ignition Control
•
•
Test Control
S-20
Gas Valve or Gas Supply Shut Off
•
Turn Valves to On Position
S-9
Faulty Induced Draft Blower
•
•
Test Blower
S-7 & 17
Broken or Shorted Igniter
•
Test Igniter
S-19
Dirty Flame Sensor, Low uA
•
Clean Flame Sensor
S-21
Flame Sensor not in Flame, Low uA
•
Test/Adjust Position of Flame Sensor
S-21
Faulty Gas Valve
•
•
•
Replace Gas Valve
S-9
Open Auxiliary Limit
•
•
Reset Control
S-6
Improper Air Flow or Distribution
•
•
Check Duct Static
S-15
Cycling on Limit
•
•
•
Check Controls & Temperature Rise
S-5 &16
Delayed Ignition
•
Test for Delayed Ignition
S-13
Flashback
•
Test for Flashback
S-14
Orifice Size
•
•
•
Check Orifices
S-11
Gas Pressure
•
•
•
•
Check Gas Pressure
S-12
Cracked Heat Exchanger
•
Check Burner Flames
S-10
Sooted Heat Exchanger
•
•
•
•
Check Flue Negative Pressure / Replace Heat Exchanger
S-10 & 23
Stuck Gas Valve
•
•
•
Replace Gas Valve
S-9
Furnace Undersized
•
Replace with Proper Size Furnace
Faulty Pressure Switch
•
•
•
Test Pressure Switch
S-17
Blocked or Restricted Flue
•
Check Flue Negative Pressure
S-17
Blocked or Restricted Drain
•
Check Coil Cover Negative Pressure
S-17
Blocked or Restricted Recuperator Coil
•
Check Coil Cover Negative Pressure
S-17
Open Roll Out Switch
•
•
Test Control
S-22
Bouncing On Pressure Switch
•
Test Negative Pressure
S-17