Williams 3508232 Owner's Manual page 29

Troubleshooting
SYMPTOM
4. Pilot lit, but main
burner won't come
ON.
5. Pilot cycles OFF and
ON by itself.
6. Main burner shuts
down before
thermostat is satisfied.
POSSIBLE CAUSE
B. Broken or shorted
electrode assembly.
A. Faulty ignition control.
B. Faulty wiring.
C. Low pilot flame.
D. Improper alignment of
sensor in pilot flame.
E. Faulty flame sensor.
A. Faulty pilot valve.
B. Faulty wiring.
A. Low pilot flame.
B. Improper alignment of
sensor in pilot flame.
C. Pilot flame being drawn
away from sensor.
D. Improper heat anticipator
setting.
E. Faulty limit.
Remove wire at "PV/MV" terminal at the ignition control, being careful not
any metal parts; disconnect the electrode wire at the ignition control. 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 end of
metal blade approx. 1/8" from terminal. Reconnect "PV/MV" terminal. Sparking should
occur between screwdriver blade and terminal.
If no sparking occurs, the ignition control 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 are tight. The ignition control
and pilot burner must both be chassis ground. If there is still no spark, the pilot and
electrode assembly must be replaced.
See 3A.
See 1F.
NOTE: Wait at least 90 seconds after pilot lights before doing the check out
procedures for problem number 4.
With thermostat ON, be sure that the pilot and sensor are properly aligned so that the
pilot flame impinges the top 3/4 inch of the sensor. Be sure that the sensor is pushed
all the way into pilot bracket. Adjust pilot flame with pilot adjustment, if necessary. Also
check inlet supply pressure and pilot orifice. If pilot hood or sensor is bent, the
defective unit should be replaced.
If 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. Attach to terminal "MV", "PV/MV" on Gas Valve. If
you read 24V and the burner won't turn ON, replace entire gas valve.
When main burner comes ON, ensure that the pilot flame is strong, sensor is properly
aligned, and pilot flame impinges the top 3/4 inch of the sensor. (See procedures for
check for 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 and pilot burner must
both be chassis ground. If there is still no spark, the pilot and electrode assembly must
be replaced.
BE SURE POWER IS "OFF" BEFORE PERFORMING THIS TEST!! Set test meter to
"ohm" scale or use continuity checker. Touch one end of probes to top of flame
sensor, the other to "SENSE" terminal on the ignition control. Ohmmeter should read
"0", continuity should be evident. If you don't obtain a reading, remove wiring from
sensor and test both individually. If continuity is not evident, replace wiring and/or
sensor.
There should be NO continuity between sensor and "GND" terminal on the ignition
control. Testing wiring and sensor individually, determine which is shorted on ground.
Replace or repair. Turn ON power.
See 2B.
See 1F.
See 4c.
See 4d.
When main burner comes ON, ensure that the pilot flame is strong, sensor is properly
aligned and pilot flame impinges the top 3/4 inch of the sensor. (See procedures for
checking for 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 the
manual valve is not in the full ON position or the inlet gas pressure with the main
burner ON. NOTE: Low inlet gas pressure to the gas control 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.
See 6c.
Check the setting of the heat anticipator in the wall thermostat. Set it to setting
specified on the gas control.
The system may be cycling on a faulty limit. Using a test meter set to the 110 volt
scale, check for a voltage reading across the limit when the main burner shuts OFF. If
you get a 24 volt or 110 volt reading on shutdown, replace defective limit switch.
CORRECTIVE ACTION
Care – 29
to touch