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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 electrical connections.
c. Burner in purge mode - allow 75 seconds for flame
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 available 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 temperature
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 adjustment is not
allowing flame to contact ignitor tip for flame rectification.
f. Misaligned ignitor does not allow flame to contact ignitor
tip for flame rectification.
Burner Short Cycling —-
Thermostat Calls for Heat, Limit Switches Closed
a. Check for polarity.
b. Check ground.
c. Check flue.
d. Check combustion air.
e. Check gas pressure.
f. Check orifice.
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 necessary.
b. Gas piping may be plugged. Check for adequate gas
supply to gas valve at union.
Burner Operates—
Insufficient Heat
a. Check thermostat for proper setting and location.
Thermostat should not be located where it will be affected
by another heat source.
b. Check for clean filter and proper air flow.
c. Check burner for proper gas firing rate.
d. Be sure unit is not undersized for its thermal load.
e. Check thermostat anticipator. The nominal anticipator
setting is 0.4.
Control Module Status Indicator - M1B* Series
a. One flash - the control is in lock-out because the
motor centrifugal switch is or was stuck closed.
b. Two flashes - the control is in lockout because the
signal was not received by the control that the
motor centrifugal switch had closed within the time.
c. Three flashes- the control is in lockout because
a failed ignition attempt, a gas valve error, or a
false flame sensed during the warm up period. If
false flame has been sensed, the control will return
to normal operation, and repeat ignition sequence
when the false flame is not present.
d. Four flashes- the control is in lockout due to a
failure within the control board.
Control Module Status Indicators - M1M Series
Control Status
The Red LED labeled “STATUS” is provided to indicate
system faults.
Steady ON:
Control OK
Steady OFF:
No power
Rapid flash:
False flame or internal control fault
One flash:
Limit switch is open
Two flashes:
Pressure switch is open
Three flashes:
Pressure switch is stuck closed
Four flashes:
Lockout due to failed ignition
Five flashes:
L1 neutral reversed or L1 voltage
not present on L1
Flame Status
A Yellow LED labeled “Flame” is provided to indicate flame
status. When flame is sensed, the flame LED is lit. If flame
sense is weak, yellow LED will flash.
