23
Combustion Blower Runs, Ignitor Heats Up
But No Flame
1. Defective pressure switch - check air tube and electrical
connections.
2. Burner in purge mode - allow 75 seconds for flame
establishing period.
3. Check for proper electrical connections at purge timer,
control box, or gas valve.
4. Check for gas supply - gas line valve on, control lever
on.
5. Check for blockage in combustion / vent pipe or heat
exchanger.
120 VAC Is Available At AMP Plug -
Ignitor Does Not Heat Up
1. Disconnect power to the furnace.
2. Disconnect AMP plug to the ignitor, and check ignitor
resistance with an ohm meter. Set on RX1 scale.
3. Check for continuity from ignitor receptacle to burner.
4. Disconnect ignitor leads at AMP receptacle and check
for 115 volts at the plug during ignition sequence.
5. Replace ignition control if 115 volts is not available at
AMP plug during ignition sequence.
Main Flame Ignites - Burner Locks Out
• Ignition control is not properly grounded.
• Defective ignition control.
• Improper polarity of 115 volt power supply.
• Ignitor has hairline crack.
• Improper gas pressure or burner air adjustment is not
allowing flame to contact ignitor tip for flame rectification.
• Misaligned ignitor does not allow flame to contact ignitor
tip for flame rectification.
Burner Short Cycling - Thermostat Calls
for Heat, Limit Switches Closed
• Check for polarity.
• Check ground.
• Check flue.
• Check combustion air.
• Check gas pressure.
• Check orifice.
24 Volts Supplied To Gas Valve During Ignition
- No Main Gas Flow
• Gas valve may be defective. Replace if necessary.
• Gas piping may be plugged. Check for adequate gas
supply to gas valve at union.
Burner Operates - Insufficient Heat
• Check thermostat for proper setting and location.
Thermostat should not be located where it will be affected
by another heat source.
• Check for clean filter and proper air flow.
• Check burner for proper gas firing rate.
• Be sure unit is not undersized for its thermal load.
• Check thermostat anticipator. The nominal setting is
0.4.
Burner Flame Without Motor Running
• Gas valve stuck open, check gas valve for proper
operation (replace if necessary) and inspect heat
exchanger.
• Check for 115 volts to the combustion blower motor;
replace if necessary.
• If no power to combustion blower then check wiring and
control module; replace if necessary.
Circulation Air Blower Will Not Operate Even
Though The Burner Does Operate
• Check thermostat G connection to the motor.
• Check 115 Volts wiring to motor.
• Check for a defective motor.
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