Troubleshooting Your Furnace - Williams FORSAIRE 4007332 Owner's Manual

TROUBLESHOOTING YOUR FURNACE

FOR MODELS: 4007732 / 6007732 / 4007731 / 6007731
* Also applicable to Models equipped with an electric intermittent pilot system.
ISSUE
1. Pilot will not stay lit
after following
lighting instructions.
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.
4. Burner comes "ON",
blower comes "ON", but
cycles "ON" and "OFF"
while burner remains
"ON".
42
FORSAIRE COUNTERFLOW DIRECT VENT GAS WALL HEATER
POSSIBLE CAUSE(S)
A. Thermocouple producing
insufficient millivolts.
B. Loose or dirty thermocouple
connection at gas valve.
C. Thermocouple defective.
D. Thermomagnet pilot safety
defective
A. Gas valve not turned ON after
lighting the pilot.
B. Electric power to furnace
turned OFF.
C. Low voltage transformer or
limit switch defective.
D. Wall thermostat defective.
E. Burner orifice plugged.
F. Gas valve defective.
A. Defective wiring.
B. Defective limit switch.
C. Defective motor (2-speed).
D. Defective motor (1-speed).
E. Detective fan switch.
A. Furnace not operating at
full rate.
CORRECTIVE ACTION
Check pilot flame – it must impinge on the thermocouple. The pilot flame
may be low or blowing (high) causing pilot to drop out. The 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.
Clean and/or tighten the thermocouple fitting at the connection to the valve.
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.
Replace gas valve after above is checked out.
Turn gas valve knob to the "ON" position - if no main gas flow, proceed to Step. "B".
Check for line voltage at furnace - if okay and no main gas flow, proceed to
Step "C".
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 the limit
switch and check for continuity across both terminals. No continuity – replace
the 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".
With thermostat set for heat (contacts closed) check for voltage at the
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. If voltage is present at the terminals on gas valve and still no gas flow
to main burners, proceed to Step "E".
Clean or replace the orifice - if okay and still no gas flow to main burners,
proceed to Step "F".
Replace defective gas valve.
Turn OFF electric power to the furnace. Remove the top front panel, fan
shroud and blower wheel. Refer to Wiring Diagram and check all wiring inside
the 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 5507331,
5507332, 6007731 & 6007732.
If the burner goes OFF in less than five minutes from room temperature start,
check the 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".
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.
Jumper across the fan switch, turn electric power ON, motor should rotate.
Replace motor if detective.
If, after checking the above possibilities, problem still exists, replace the fan
switch.
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.