Instructions / Assembly

Troubleshooting
46
TROUBLESHOOTING CHART FOR MODELS FOR MODELS: 4007332; 5507332; 4007331; 5507331
NOTE: Before troubleshooting the intermittent pilot system, be sure thermostat is turned to highest setting, gas shut-off valve and gas
valve knob are in the ON position, and electric power is turned ON the furnace. Follow all steps in sequence. A volt-ohm meter will be
needed to satisfactorily determine if any components are malfunctioning.
SYMPTOM POSSIBLE CAUSE CORRECTIVE ACTION
1. No spark – no pilot
gas.
A. No main power.
Perform normal system checks of the main power, transformer, thermostat, limit
switch, and replace faulty components.
With the power ON, turn the thermostat to the lowest setting, wait for 10 seconds and
return to HIGH setting. With the power ON and thermostat set at its highest position,
set voltmeter to 24V scale and attach the probes to terminals "TR" and "TH" on the
ignition control unit.
If you read 24V and there still is no spark or pilot gas, the ignition control unit is
defective and must be replaced.
B. Faulty transformer.
C. Faulty thermostat.
D. Faulty limit switch.
E. Faulty ignition control.
F. Faulty wiring. Test wiring. Repair or replace.
2. Spark – but no pilot
gas.
A. Faulty ignition. See 1E.
B. No gas supplied to pilot
valve.
Check for availability of gas at gas control valve. Make sure the manual valve (gas
cock) on the gas control are in the full ON position.
No pilot gas could be caused by plugged pilot tubing. Also check the pilot
adjustment at the gas control valve.
C. Manual valves in OFF
position.
D. Faulty pilot valve.
E. Faulty wiring. See 1F.
F. Restricted pilot line or
clogged pilot orifice.
See 2B.
3. Pilot gas – but no
spark.
A. Faulty ignition control.
With power ON, turn the thermostat to the lowest setting, wait for 10 seconds and then
return it to the high setting. With power ON and thermostat set at its highest position,
set voltmeter to 24V scale and attach probes to terminals “TR” and “TH” on the ignition
control unit. If you read 24V and there is still no spark or pilot gas, the ignition control
is defective and must be replaced.
With thermostat turned to its highest setting, set test meter to 24V scale.
Touch probes to "C" and "P" terminals on the Gas Control Valve. If you do not get a
24V reading, check wiring. If wiring tests okay, check the ignition control unit.
B. Broken or shorted
electrode assembly.
Remove wire at "COM" terminal at the ignition control unit, being careful not to touch
any metal parts; disconnect the electrode wire at the ignition control unit. Connect one
end of a jumper wire to terminal "GND". (DO NOT REMOVE EXISTING WIRE.) Attach
the other end of the jumper wire to the metal blade of a small screwdriver. Position the
end of metal blade approx. 1/8" from the “HIGH VOLTAGE” (IGN) terminal. Reconnect
the "COM" terminal. Sparking should occur between the screwdriver blade and the
“HIGH VOLTAGE” terminal.
If no sparking occurs, the ignition control unit must be replaced.
Check the pilot and electrode assembly for proper electrode gap (3/32" to 1/8") or any
possible shorting of electrode to surrounding metal surfaces. Make sure the spark
igniter and electrode connections to the ignition control unit are tight. The ignition
control unit and pilot burner must both be chassis ground. If there is still no spark, the
pilot and electrode assembly must be replaced.
4. Pilot lit, but main
burner won't come
ON.
A. Faulty ignition control
unit.
See 3A.
B. Faulty wiring. See 1F.