Williams 3508631 Bedienungshandbuch PDF herunterladen (Seite 27)

Troubleshooting

Care – 27

FOR MODELS: 3508631; 3508632; 5008631; 5008632; 6508631; 6508632

*Also applicable to Models equipped with an electric intermittent pilot system. (Continued on next page)

SYMPTOM

POSSIBLE CAUSE

CORRECTIVE ACTION

1. Pilot will not stay lit

after following lighting

instructions.

A. Thermocouple producing

insufficient millivolts.

Check pilot flame – it must impinge on thermocouple. Pilot flame may be low or

blowing (high) causing safety to drop out. Pilot orifice or aerating hole may be plugged

(check for spiders, webs or other organic material). Be sure the thermocouple is fully

inserted in its bracket.

B. Loose or dirty

thermocouple

connection at gas valve.

Clean and/or tighten the thermocouple fitting at the connection to the valve.

C. Thermocouple defective.

Check thermocouple with millivolt meter – it should generate approximately 30

millivolts when not connected to a load. When connected to a load, it should generate

approximately 14 millivolts. If below 7 millivolts, replace.

D. Thermomagnet pilot

safety defective

Replace gas valve after above is checked out.

E. Vent safety shutoff

device.

Check wiring connections from valve to the vent safety shutoff device. Be sure all

connections are tight. Check for blocked or incorrect venting.

2. Main burner will not

come ON - pilot

burning and

thermostat set for

heat.

A. Gas valve not turned ON

after lighting the pilot.

Turn gas valve knob to 'ON" position - if no main gas flow, proceed to Step. "B".

B. Electric power to furnace

turned OFF.

Check for line voltage at furnace - if okay and no main gas flow, proceed to Step "C".

C. Low voltage transformer

or limit switch defective.

Check for 24 volts at the low voltage terminals of the transformer. If no voltage, turn

OFF electric power to furnace. Remove one wire from limit switch and check for

continuity across both terminals. No continuity – replace limit switch. With a good limit

switch back 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, proceed to Step "D".

D. Wall thermostat

defective.

With thermostat set for heat (contacts closed) check for voltage at terminals on gas

valve. If no voltage is present replace defective thermostat. NOTE: Before replacing

thermostat, be sure to check the wiring from the furnace to thermostat for loose

connections or broken wires and replace as needed.

E. Burner orifice plugged.

Clean or replace orifice - if okay and still no gas flow to main burners, proceed to Step

"F".

F. Gas valve defective.

Replace defective gas valve.

3. Burner comes "ON"

but goes OFF before

blower turns ON.

A. Defective wiring.

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 switches. Correct if necessary. If correct, proceed to Step "B".

NOTE: Selector switch used only on Models 5008731; 5008732; 6508731; 6508732.

B. Defective limit switch.

If burner goes OFF in less than five minutes from room temperature start, check limit

control switch. If detective, replace. NOTE: Blower should turn "ON" within three

minutes after burner is "ON" from a room temperature start. If not, proceed to Step

"C”.

C. Defective motor (2-

speed).

Jumper across the fan switch, turn electric power ON, the motor should rotate. If a 2-

speed motor is used - jumper from "brown" terminal on the fan switch to #2 (red)

terminal on the selector switch, motor should rotate on "LOW" speed. Jumper from

same "brown" terminal on the fan switch to #3 (black) terminal on the selector switch,

motor should rotate on "HIGH" speed. Replace motor if defective.

D. Defective motor (1-

speed).

Jumper across fan switch, turn electric power ON, motor should rotate. Replace motor

if detective.

E. Detective fan switch.

If, after checking above possibilities, problem still exists, replace fan switch.

4. Burner comes "ON",

blower comes "ON",

but cycles "ON"

and "OFF" while

burner remains "ON".

A. Furnace not operating at

full rate.

Check for low gas pressure at gas valve - should be 4" W.C. for Natural Gas, 11" W.C.

for L.P. Gas. Check burner orifice.

5. Burner comes "ON",

blower comes "ON",

but burner cycles

"OFF" and "ON" with

blower "ON".

A. Furnace operating over-

rate.

Check for high gas pressure at gas valve - correct if necessary. See correct pressure

above.

B. Line voltage too low.

Check line voltage to motor, if below 115 volts motor will run too slow.

C. Recirculation.

Heated air discharging against an object causing recirculation, such as a hall

installation or a large piece of furniture within 4' of discharge.

D. Loss of circulating air

due to leakage.

Check header plate installation and proper use of gaskets. Repair as necessary.

6. Furnace operates but

turns "OFF" before

A. Thermostat location.

Check location of thermostat. It should not be in the path of warm air discharge from

the furnace, near a lamp, or above a TV set or stereo.

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