Lennox Hearth EN54-VDLE - Manual (Page 16)

6 NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE.
TROUBLESHOOTING THE MILLIVOLT GAS CONTROL SYSTEM
. Spark ignitor will not light
pilot after repeated triggering
of ignitor button.
2. Pilot will not stay lit after
carefully following the light-
ing instructions.
3. Pilot burning, no gas to
burner, Valve knob “ON,”
Wall Switch “ON.”
. Frequent pilot/burner outage
problem.
correctiVe action sYMptoM
a. Defective ignitor
(no spark at electrode).
B. Defective or misaligned electrode
at pilot (spark at electrode).
c. Gas supply pressure errant.
d. Pilot orifice plugged.
a. Defective pilot generator
(thermocouple).
a. Wall switch or wires defective.
B. Thermopile may not be generating
sufficient millivoltage.
c. Plugged burner orifice.
a. Pilot flame may be too low or
blowing (high) causing the pilot/
valve safety to drop out.
Check for spark at electrode and pilot; if no spark and electrode
wire is properly connected, replace ignitor.
possiBLe causes
Note: Before troubleshooting the gas control system, be sure external gas shut off valve (located at gas supply inlet) is
in the “ON” position.
Important: Valve system troubleshooting should only be accomplished by a qualified service technician.
Clean and/or adjust pilot flame for maximum flame impinge-
ment on thermocouple (Figure 9 on page 8 ).
Check burner orifice for stoppage and remove.
Check thermopile with millivolt meter. Take reading at thermo-
pile terminals of gas valve. Should read 325 millivolts minimum
with optional wall switch “OFF.” Replace faulty thermopile if
reading is below specified minimum.
Check wall switch and wires for proper connections. Jumper
wire across terminals at wall switch, if burner comes on, re-
place defective wall switch. If okay, jumper wires across wall
switch wires at valve, if burner comes on, wires are faulty or
connections are bad.
Check pilot flame, it must impinge on thermocouple (Figure
9 on page 8) Clean and/or adjust pilot for maximum flame
impingement on thermocouple. Ensure that the connection
between the valve and thermocouple are tight and secure.
Clean or replace pilot orifice.
Check inlet gas pressure. It should be within the limits as
marked on the rating plate.
Using a match, light pilot. If pilot lights, turn off pilot and trig-
ger the ignitor button again. If pilot lights, an improper gas
mixture caused the bad lighting and a longer purge period is
recommended. If pilot will not light – check gap at electrode and
pilot – should be 1/8" to have a strong spark. If gap measures
1/8", replace pilot (Figure 9 on page 8 ).