Troubleshooting - Williams 4003532 Owner's Operation And Installation Manual

TROUBLE-
SHOOTING
AWARNING
Turn off and unplug furnace and let cool before servicing. Unless
you need gas supply for testing, shut off manual shutoff valve
before servicing. Only a qualified service person should service
and repair furnace.
COMPLAINT--NO HEAT
1. Thermostat Off
Check to be sure thermostat is calling for heat. Wire to thermostat could be off
terminal.
2. Gas Supply
Be sure manual gas valve is in the open position (level or parallel to gas line).
3. Electrical Connections and Power
Be sure all electrical connections are secure.
4. Motor
Motor must be operating at top speed before burner will come on. If blower is not
operating at top speed, check voltage supply (minimum 100 volts A.C.). If voltage
supply is okay, check for defective motor.
5. Malfunctioning Microswitch
Be sure the microswitch is sailing in far enough to open the solenoid valve and to
energize the ignition control. If the switch is not sailing in, clean any dust or dirt from
the actuator pin. Other reasons for the switch not sailing in are:
A. Insufficient blower speed - Slow motor due to faulty motor or lint and dust
accumulation on the blower wheels or restriction of return air to the furnace.
B. Faulty microswitch - Replace switch ifcircuit to ignition control is not completed
when switch is manually engaged. Switch should also be replaced if blower
motor running at top speed fails to engage switch within six or seven seconds.
Note: To service switch, combustion chamber must be pulled out. Follow steps
1, 2, 3, 9 and 10on pages 14 and 15 to remove combustion chamber.
6. Gas Valve
Within 20 seconds after motor reaches 75% of its r.p.m, and microswitch engages,
check the following:
A. Voltage at valve - If current is present but valve is not opening, check wire
connections.
B. If wire connections okay - Replace valve.
C. No voltage at valve - Check circuit completion through microswitch and limil
switch as well as wiring and wire connections. If no defects are found, see ste
9 under Igm'tion Failures, page 26.
7. Blower Not Operating
A. Check power supply to furnace.
B. Check electrical connections at furnace.
C. With thermostat points closed, check for circuit completion at motor. If voltag_
is present, replace motor. If no voltage is present at motor, check for:
• 24 volts on secondary coil or transformer. If no voltage, replace transformer
• If 24 volt transformer okay, check for circuit completion across contacts or
time delay relay. Allow three to five seconds for contact to close.
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