Instructions / Assembly

Troubleshooting
Care – 47
SYMPTOM POSSIBLE CAUSE CORRECTIVE ACTION
C. Low pilot flame.
NOTE: Wait at least 90 seconds after pilot lights before doing the check out
procedures for problem number 4.
With the thermostat ON, be sure that the pilot and sensor are properly aligned so that
the pilot flame impinges the top 5/8 inch of the sensor. Be sure that the sensor is
pushed all the way into the pilot bracket. Adjust the pilot flame with pilot adjustment
screw, if necessary. Also check the inlet supply pressure and pilot orifice. If the pilot
hood or sensor is bent, the defective unit should be replaced.
If the main burner still won't come ON, make sure the main burner orifices are clear. If
orifices are clear, set voltmeter to 24V scale and touch probes to the terminals of the
main gas operator on the gas valve. Touch probes to terminal "M", "C" on Gas Valve.
If you read 24V and the burner won't turn ON, replace entire gas valve.
D. Improper alignment of
sensor in pilot flame.
When the main burner comes ON, ensure that the pilot flame is strong, the sensor is
properly aligned, and the pilot flame impinges the top 5/8 inch of the sensor. (See
procedures for checking proper pilot flame and alignment in problem 4c.) 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 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.
E. Faulty flame sensor.
BE SURE POWER IS "OFF" BEFORE PERFORMING THIS TEST!! Set test meter to
the "ohm" scale or use continuity checker. Touch one end of the probe to tip of flame
sensor, the other to the "SENSE" terminal on the ignition control unit. The Ohmmeter
should read "0", continuity should be evident. If you don't obtain a reading, remove
wiring from the sensor and test both individually. If continuity is not evident, replace
the wiring and/or sensor.
There should be NO continuity between sensor and "GND" terminal on the ignition
control unit. Test wiring and sensor individually, determine which is shorted on ground.
Replace or repair. Turn ON power.
5. Pilot cycles OFF and
ON by itself.
A. Faulty pilot valve. See 2B.
B. Faulty wiring. See 1F.
6. Main burner shuts
down before
thermostat is satisfied.
A. Low pilot flame. See 4c.
B. Improper alignment of
sensor in pilot flame.
See 4d.
C. Pilot flame being drawn
away from sensor.
When main burner comes ON, ensure that the pilot flame is strong, sensor is properly
aligned and pilot flame impinges the top 5/8 inch of the sensor. (See procedures for
checking for the proper pilot flame and alignment in problem 4d.) If the pilot flame is
drawn away from the sensor when the main burner comes "ON" the cause could be
that the manual valve is not in the full ON position.
NOTE: Low inlet gas pressure to the gas control valve can be caused by several
problems and is not within the scope of the procedures outlined in this service guide.
Consult your local utility or gas supplier.
D. Improper heat anticipator
setting.
See 6c.
Check the setting of the heat anticipator in the wall thermostat. Set it to the setting
specified on the gas control valve.
E. Faulty limit switch.
The system may be cycling on a faulty limit switch. Using a test meter set to the 110
volt scale, check for a voltage reading across the limit switch when the main burner
shuts OFF. If you get a 24 volt or 110 volt reading on shutdown, replace defective limit
switch.