25
INTERMITTENT PILOT TROUBLESHOOTING
A. Intermittent Pilot
Ignition System Checks
STEP 1:
Check ignition cable.
• Verify ignition cable does not make contact with metal
surfaces.
• Verify only factory supplied Ignition cable (or approved
replacement) is used.
• Verify connections to ignition module and igniter or
igniter-sensor are clean and tight.
• Verify ignition cable provides good electrical continuity.
STEP 2:
Verify ignition system grounding. Nuisance shutdowns are
often caused by poor or erratic grounding.
Common ground is required for module and pilot burner/
igniter sensor.
— Check for good metal-to-metal contact between
pilot burner bracket and the main burner.
— Check ground lead from GND (BURNER) terminal
on module to pilot burner. Verify connections are
clean and tight. If wire is damaged or deteriorated,
replace with No. 14-18 gauge, moisture-resistant,
thermoplastic insulated wire with 105°C [221°F]
minimum rating.
— Check ceramic flame rod insulator for cracks or
evidence of exposure to extreme heat, which can
permit leakage to ground. Replace pilot burner/igniter
sensor and provide shield if necessary.
— If flame rod or bracket is bent out of position, restore
to correct position.
STEP 3:
Check spark ignition circuit.
Disconnect ignition cable at SPARK terminal on module.
WARNING
Electrical shock hazard. Ignition circuit generates
over 10,000 volts. Turn OFF electrical power
supply at service panel before making electrical
connections. Failure to do so could result in
death or serious injury.
!
Energize module and listen for audible sparking noise.
When operating normally, there should be a buzzing noise
that turns on and off twice per second for duration of 1–7
seconds depending on model.
STEP 4:
Verify pilot and main burner lightoff.
• Initiate call for heat. Turn thermostat above room
temperature. Ignition sequence may be delayed by
thermal purge up to 2 minutes.
• Watch pilot burner during ignition sequence.
— Verify ignition spark continues after pilot is lit.
— Verify pilot lights and spark stops, verify main
burner does not light.
•
If so, ensure adequate flame current as follows.
— Turn off boiler at circuit breaker or fuse box.
— Clean flame rod with emery cloth.
— Verify electrical connections are clean and tight.
Replace damaged wire.
— Check for cracked ceramic insulator, which can
cause short to ground, and replace igniter-sensor if
necessary.
— At gas valve, disconnect main valve wire from MV
terminal.
— Turn on power and set thermostat to call for heat. Pilot
should light, main burner will remain off because main
valve actuator is disconnected.
— Check pilot flame. Verify it is blue, steady and
envelops 3/8 to 1/2 in. [10 to 13 mm] of flame rod.
See Figure 20 for possible flame problems and causes.
— If necessary, adjust pilot flame by turning pilot
adjustment screw on gas control clockwise to decrease
or counterclockwise to increase pilot flame. Following
adjustment, always replace pilot adjustment cover
screw and tighten firmly to assure proper gas control
operation. Figure 16, page 18.
— Set temperature below room set-point to end call for
heat.
P/N
240009041
, Rev. C [04/30/2017]
