26
LENNOX HEARTH PRODUCTS • MERIT
®
SERIES DIRECT-VENT GAS FIREPLACES • MODELS MLDVT-30/35/40/45 • CARE AND OPERATION INSTRUCTIONS
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 14 on Page 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
instructions.
A. Defective pilot generator
(thermocouple).
Check pilot ame, it must impinge on thermocouple (see Figure 14 on Page 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,” and the
(standard) burner
OFF/ON switch is
“ON."
NOTE: If an optional*
remote switch is
used for burner
operation, if the
standard burner
OFF/ON switch is
still installed on
appliance it must be
in the "OFF" position.
A. 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.
B. Thermopile may not be
generating sufficient
millivolts.
Check thermopile with millivolt meter. Take reading at thermopile terminals of gas
valve. Should read 325 millivolts minimum with optional wall switch “OFF.” Replace
faulty thermopile if reading is below specified minimum.
C. Plugged burner orifice.
Check burner orice for blockage and remove.
D. OFF/ON Switch and
*Remote Switch are in the
"ON" position resulting in
excessive resistance.
When turning on the burner using a *remote switch, ensure that the standard OFF/ON
switch is in the "OFF" position. If both switches are in the ON position, it may result in
excessive resistance (and millivolt drainage) and the burner may not come on.
4. Frequent pilot/burner
outage problem.
A. Pilot flame may be too low
or blowing (high) causing
the pilot/valve safety to
drop out.
Clean and/or adjust pilot flame for maximum flame impingement on thermocouple
(see Figure 14 on Page 16).
* Optional remote switch kits—wall switch, wall thermostat or remote control.
TROUBLESHOOTING GUIDE: MILLIVOLT GAS CONTROL SYSTEM
Note: Before troubleshooting the gas control system, make sure the external gas shut off valve (located at gas supply inlet) is in the
“ON” position.
Note: Valve system troubleshooting should only be performed by a qualified service technician.
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