22
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT
®
SERIES B-VENT GAS FIREPLACES • 36" LMBV MODELS • CARE AND OPERATION INSTRUCTIONS
TROUBLESHOOTING GUIDE - MILLIVOLT GAS CONTROL SYSTEM
NOTE: Before troubleshooting the gas control system, Ensure external gas shut off valve, located at gas supply inlet, (and wall switch, iff applicable),
is in the “ON” position.
Important: Valve system troubleshooting should only be accomplished by a qualified service technician.
SYMPTOM
POSSIbLE CAUSES
CORRECTIvE ACTION
1.
Spark igniter will not light pilot after
repeated triggering of igniter button.
WARNING: if the pilot will not light
after 1 minute of attempting, wait for at
least 5 minutes for gas to clear before
attempting again.
A.
Defective igniter
(no spark at electrode).
Check for spark at electrode and pilot; if no spark and electrode
wire is properly connected, replace igniter.
b.
Defective or misaligned electrode at pilot (spark
at electrode).
Using a match, light pilot. If pilot lights, turn off pilot and
trigger the igniter 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
(see
Figure
16
)
.
C.
Gas supply pressure errant.
Check inlet gas pressure. It should be within the limits as
marked on the rating plate.
D.
Pilot orifice plugged.
Clean or replace pilot orifice.
2.
Pilot will not stay lit after
carefully following the lighting instruc-
tions.
A.
Defective pilot generator
(thermocouple).
Check pilot flame, it must impinge on thermocouple (see
Figure 16
).
Clean and/or adjust pilot for maximum flame
impingement on thermocouple. Ensure that the connection
between the valve and thermocouple are tight and secure.
3.
Pilot burning, no gas to burner, Valve
knob “ON,” Wall Switch “ON.”
*
Optional remote switch kits - wall
switch or timer, or remote control.
A.
Damper closed or Damper Switch defective.
Ensure damper control lever is locked in the open position,
all the way to the right. If the damper control lever is locked
in the open position troubleshoot through Steps B, C and
D below. If the main burner will still not light, determine
if the damper switch is defective and replace if necessary.
b.
Wall switch or wires defective.
Check wall switch and wires for proper connections. Jumper
wire across terminals at wall switch, if burner comes on,
replace defective wall switch. If okay, jumper wires across
wall switch wires at valve, if burner comes on, wires are
faulty or connections are bad.
C.
Thermopile may not be generating sufficient
millivolts.
Check thermopile with millivolt meter. Take reading at ther-
mopile terminals of gas valve. Should read 325 millivolts
minimum with optional wall switch “OFF.” Replace faulty
thermopile if reading is below specified minimum.
D.
Plugged burner orifice.
Check burner orifice for blockage and remove.
4.
Frequent pilot/burner outage problem.
A.
Pilot flame may be too low or blowing (high) caus
-
ing the pilot/valve safety to drop out.
Clean and/or adjust pilot flame for maximum flame impinge-
ment on thermocouple (see
Figure 16
).
SYMPTOM
POSSIbLE CAUSES
CORRECTIvE ACTION
1.
Burner will not light.
A.
Damper closed or Damper Switch defective. Ensure damper control lever is locked in the open position,
all the way to the right. If the damper control lever is locked
in the open position troubleshoot through Steps B, C and
D below. If the main burner will still not light, determine
if the damper switch is defective and replace if necessary.
b.
Faulty Valve System.
See
Page 23
.
C.
Faulty limit switch.
Reset the limit switch button. If still not working, access the
leads attached to the limit switch and check for continuity.
If no continuity, replace limit switch.
D.
“OFF/ON” or wall switch defective.
Disconnect the two black wires from the wire nuts. Test
switch(s) for continuity with a multimeter. If continuity is
not indicated, switch(s) is defective and must be replaced.
Note:
Before replacing “OFF/ON” switch, Ensure to check
wiring for loose connections or broken wires and repair
as needed.
2.
Burners come “ON,” then turns “OFF.”
A.
Burner orifice plugged.
Check main burner orifice(s) for blockage. Clean or replace.
b.
Obstructed vent system.
Check vent system for obstructions.
TROUbLESHOOTING
TROUBLESHOOTING GUIDE - ELECTRONIC IGNITION SYSTEM
