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Main Flame Is Not Burning Properly
a. Check the manifold gas pressure.
b. Check for the correct main burner orifi ce.
- See the nameplate SPECIFICATION.
c. Check the fl ue for any blockages or loose
connections.
d. Check the combustion air passages for blockage.
High Gas Bills
a. Be sure the proper orifi ces are being used.
b. Be sure the return air system is clear and free
of blockage.
c. Be sure the furnace fi lter is clean.
d. Be sure the home is insulated, that windows
and doors fi t tightly, and that there are no
leaks in the heating duct system.
e. Check the room thermostat to be sure the
setting is not higher than necessary. Low
humidity requires higher temperatures for
the same level of comfort. Check for proper
humidity level in the home.
TROUBLESHOOTING - DIRECT IGNITION
FURNACES INCLUDING GAS GUN
Burner Motor Does Not Run—
Thermostat Calls For Heat
a. Check the electrical supply to the furnace.
b. Be sure the furnace On-Off switch is in the
“ON” position.
c. Defective thermostat circuit - white and red
thermostat low voltage leads (M1M*, M1B*
models). If the burner motor or combustion
fan runs, check:
• Thermostat
connections
• Thermostat
d. No voltage to control module - determine if 24
volts (or 120 volts) is available to the control
module. If voltage is not available check
for:
• Blown fuse, defective transformer, circuit
breaker, no electrical supply.
• Limit switch open.
• Loose connections.
Combustion Blower Does Run - No Flame
a. Defective centrifugal switch (M1B* Model).
• Check the operation of centrifugal switch by
removing end bell of the burner motor.
• Clean contacts of motor.
• If the contacts are closed, replace the motor.
b. Defective pressure switch (M1M* and M1G*
077, 090 Models) - check air tube and electri-
cal connections.
c. Burner in purge mode - allow 75 seconds for
fl ame establishing period.
d. Check for proper electrical connections at
purge timer, control box, or gas valve.
e. Check for gas supply - gas line valve on,
control lever on.
Control Module Is Powered—
Ignitor Does Not Heat Up
a. Disconnect ignitor leads at AMP receptacle
and check for 120 volts at the plug during
ignition sequence.
b. Replace ignition control if 120 volts is not avail-
able at AMP plug during ignition sequence.
120 Volts Is Available At AMP Plug—
Ignitor Does Not Heat Up
a. Disconnect power to the furnace.
b. Disconnect AMP plug to the ignitor, and check
ignitor resistance with an ohm meter. Set on
RX1 scale.
• Normal reading should be 40 - 75 ohms.
• If above or below this rating at room tem-
perature change ignitor.
c. Check for continuity from ignitor receptacle
to burner.
Main Flame Ignites—
Burner Locks Out
a. Ignition control is not properly grounded.
b. Defective ignition control.
c. Improper polarity of 120 volt power supply.
d. Ignitor has hairline crack.
e. Improper gas pressure or burner air adjust-
ment is not allowing fl ame to contact ignitor
tip for fl ame rectifi cation.
f. Misaligned ignitor does not allow fl ame to
contact ignitor tip for fl ame rectifi cation.
Burner Short Cycling —-
Thermostat Calls for Heat, Limit Switches
Closed
a. Check for polarity.
b. Check ground.
c. Check fl ue.
d. Check combustion air.
e. Check gas pressure.
f. Check orifi ce.
g. Check the position of ignitor, a normal reading
should be 40-75 ohms.
24 Volts Supplied To Gas Valve During
Ignition —
No Main Gas Flow
a. Gas valve may be defective. Replace if neces-
sary.
b. Gas piping may be plugged. Check for ad-
equate gas supply to gas valve at union.
Burner Operates—
Insuffi cient Heat
a. Check thermostat for proper setting and loca-
tion. Thermostat should not be located where
