Williams 5508332 - Troubleshooting Common Issues

Troubleshooting Chart
FOR MODELS: 3508731; 3508732; 5008731; 5008732; 6508731; 6508732
SYMPTOM
1. Pilot willnot 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 furnaceturned
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 -- mustimpinge onthermocouple.Pilotflame
maybe loworblowing (high)causingsafetyto dropout. Pilo_orifice
or aeratinghole maybe plugged (check for spiders,webs or other
organic material). Be sure the thermocouple is fully insertedin
bracket.
b. Clean and/ortightenthermocouplefitting atconnectionto valve.
C. Check thermocouplewithmillivoltmeter-- shouldgenerateap-
proximately30 millivolts when not connected to load. When con-
nectedtoload,shouldgenerateapproximately14millivolts.If below
7 miilivolts, replace.
d. Replace gas valve after above is checked out.
e. Checkwiringconnectionsfrom valve to vent safetyshutoffdevice.
Be sure all connections are tight. Check for blocked vent.
a.
b.
C.
d.
e.
f.
Turngasvalve knob to "ON" position -- if no main gas flow, pro-
ceed to Step. "b".
Checkforline voltage at furnace-- if okayand no main gasflow,
proceed to Step "c".
Checkfor24 voltsatthe lowvoltage terminals of thetransformer.
If novoltage,turn OFFelectric powerto furnace.Removeone wire
from limit switch and check for continuity across both terminals.
No continuity-- replacelimit switch.With a good limit switchback
in the circuitand the electric powerturned 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 sureto
checkwiring from furnace to thermostat for loose connectionsor
broken wiresand replace as needed.
If voltage is present at terminals on gas valve and still nogas flow
to main burners, proceed to Step "e".
Clean or replace orifice -- if okay and still nogas flow to main
burners, proceed to Step "f".
Replace defective gas valve.
a.
b.
Turn OFF electric power to furnace. Removetop front panel, fan
shroud and blower wheel. Refer to Wiring Diagram and check all
wiring inside junction box. Removecenter front panel and check
all wiring inside switch box containing fan, limit and selectorswit-
ches.Correct if necessary.If correct, proceed to Step "b". NOTE:
Selectorswitch used only on Models5008731;5008732;6508731:
6508732.
If burner goes OFF in less than five minutes from room
temperaturestart, check limit control switch. If defective,replace.
NOTE:Blower should turn "ON" within three minutesafter burner
is "ON" froma room temperaturestart. If not, proceedtoStep "c".
*Also applicabLeto Models equipped with an electric intermittent pilot system. (continued next page)
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