Download Gas Furnace – Troubleshooting Spark Ignition

Gas Furnace – Troubleshooting
Spark Ignition
Start
Inducer Motor
Runs?
No
24 Volts on
“R” Terminal?
No
120 Volts to
Furnace?
No
Check:
Thermostat,
Low Voltage Wiring
Yes
24 Volts on
“W” Terminal?
Yes
Yes
120 Volts to
Inducer Motor?
No
Replace:
Control Board
Yes
Replace:
Inducer Motor
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Page 1
No
Check: Fuse,
Circuit Breaker,
Door Switch,
Line Voltage Wiring
24 Volts on
Both Sides of
Pressure
Switch?
No
Is Venting
Plugged?
No
Is Inducer
Mtr Port or Hose
Plugged?
Yes
Yes
Clear Inducer Mtr
Port or Hose
Clear Venting
Yes
Spark Igniter
Sparking?
No
24 Volts to
Spark Module?
No
Check:
Limits and Safeties
No
Clean Spark
Head
Yes
Is Spark Head
Clean?
Yes
Yes
Replace:
Spark Module
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Page 2
No
Is Inducer
Mtr Pulling
Proper Inches
W.C.?
Yes
Replace:
Pressure Switch
No
Replace:
Inducer Motor
Pilot Ignites?
No
24 Volts on
PV terminal of
Gas Valve?
No
Replace:
Control Board
Yes
Gas Coming
Out of Pilot
Port on Gas
Valve?
Yes
No
Is Gas Coming
Into the Gas
Valve?
Yes
Yes
Clear Pilot Tube
And Pilot Head
Burners
Ignite?
No
24 Volts on
MV terminal of
Gas Valve?
Replace:
Gas Valve
No
Replace:
Control Board
Yes
Yes
Do Burners
Stay On?
Replace:
Gas Valve
No
Clean/Replace:
Flame Sense
Device
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Page 3
No
Check:
Gas Meter and
Gas Shut-off
Blower Turns
On?
No
120 Volts to
Blower Motor?
No
Replace:
Control Board or
Fan Control
Yes
Replace:
Blower Motor
Yes
Does House
Heat to Set
Temperature?
No
Is It a High
Efficiency
Furnace?
Yes
Check:
For Plugged
Condensation Tube
Or Trap
Stop
No
Check:
Air Flow, Filter, Dirty
A/C Coil, Blocked
Return Air Grille,
Overheating