Troubleshooting Chart - Williams 5508332 Owner's Manual

Troubleshooting Chart
FOR MODELS: 3508731; 3508732; 5008731; 5008732; 6508731; 6508732
SYMPTOM
1. Pilot will not stay lit after
following lighting
instructions.
POSSIBLE CAUSE(S)
a. Thermocouple producing insuffi-
cient millivoltage.
2. Main burner will not come
ON -- pilot burning and
thermostat set for heat.
"3. Burner comes "ON" but
goes OFF before blower
turns ON.
b. Loose or dirty thermocouple
connection at gas valve.
c. Thermocouple defective.
d. Thermomagnet pilot safety
defective.
e. Vent safety shutoff device.
a. Gas valve not turned ON.
b. Electric power to furnace turned
OFE
c. Low voltage transformeror limit
switch defective.
d. Wall thermostat defective.
e. Burner orifice plugged.
f. Gas valve defective.
a. Defective wiring.
b. Defective limit switch.
CORRECTIVE ACTION
a.
Check pilotflame -- must impinge onthermocouple.Pilotflame
may be low or blowing (high)causing safetyto drop out. Pilo_orifice
or aerating hole may be plugged (check for spiders, webs or other
organic material). Be sure the thermocouple is fully insertedin
bracket.
b. Clean and/or tightenthermocouplefitting at connection to valve.
C.
Check thermocouple with millivoltmeter-- shouldgenerateap-
proximately 30 millivolts when not connected to load. When con-
nectedto load,should generateapproximately14millivolts.If below
7 miilivolts, replace.
d. Replace gas valve after above is checked out.
e. Check wiringconnections from valve to vent safetyshutoff d evice.
Be sure all connections are tight. Check for blocked vent.
a.
b.
C.
d.
e.
f.
Turngas valve knob to "ON" position -- if no main gas flow, pro-
ceed to Step. "b".
Check forline voltage at furnace-- if okay and no main gas flow,
proceed to Step "c".
Check for24 volts at the lowvoltage terminals of the transformer.
If no voltage,turn OFF electric power to furnace. Removeone wire
from limit switch and check for continuity across both terminals.
No continuity -- replacelimit switch.With a good limit switchback
in the circuit and the electric power turned ON -- if no voltage,
replace transformer. NOTE: Before replacing the transformer or
limit switch, check wiring for loose connections or broken wires
and repair as needed. If voltage is present at transformer, pro-
ceed to Step "d".
With thermostat set for heat (contacts closed) checkfor voltage
at terminals on gas valve. If no voltage is present replace defec-
tive thermostat. NOTE: Before replacing thermostat, be sure to
check wiring from furnace to thermostat for loose connections or
broken wiresand replace as needed.
If voltage is present at terminals on gas valve and still no gas flow
to main burners, proceed to Step "e".
Clean or replace orifice -- if okay and still no gas flow to main
burners, proceed to Step "f".
Replace defective gas valve.
a.
b.
Turn OFF electric power to furnace. Remove top front panel, fan
shroud and blower wheel. Refer to Wiring Diagram and check all
wiring inside junction box. Remove center front panel and check
all wiring inside switch box containing fan, limit and selector swit-
ches. Correct if necessary. If correct, proceed to Step "b". NOTE:
Selectorswitch used only on Models 5008731;5008732;6508731:
6508732.
If burner goes OFF in less than five minutes from room
temperature start, check limit control switch. If defective,replace.
NOTE:Blower should turn "ON" within three minutes after burner
is "ON" from a room temperature start. If not, proceed to Step "c".
*Also applicabLeto Models equipped with an electric intermittent pilot system. (continued next page)
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