Service Manual

SYSTEM OPERATION
62
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 Wiri ng S-3A
No Low Voltage
•
Check Transformer S-4
Faulty Thermostat
•••••
Check Thermostat S-3A
Fa ult y Tra nsformer
•
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 (ECM)
••
Test Blower Motor (& 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
Fa ult y 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 Limit
•• •
Check Controls & Temperature Rise S-201 / S-300
Delayed Ignition
•
Test for Delayed Ignition S-312
Fl ashback
•
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 Swi tch
••
Test Flame Roll Out Control S-302
Bouncing On Pressure Swi tch
•
Test Negative Pressure S-310