5894307-UIM-B-0920
30 Johnson Controls Ducted Systems
4 Red Flashes: Indicates the high limit switch is open. The main limit
switch has opened its normally closed contacts. The control operates
the supply air blower and inducer while the open limit condition exists.
Check for the following:
• Dirty filter
• Incorrectly sized duct system
• Incorrect blower speed setting
• Incorrect firing rate
• Loose limit switch wiring
• Faulty blower motor
If the main limit switch opens five times within a single call for heat, the
control indicates 4 Red Flashes and enters a 1-h soft lockout.
5 Red Flashes: Indicates flame is present with the gas valve off. The
control board has sensed a flame during a period when the gas valve is
not supposed to be open. Check for miswiring. The control enters a
hard lockout. After the problem is corrected, you must turn off the power
and turn on the power again to reset the control.
6 Red Flashes: Indicates the auxiliary limit switch is open. The limit
switch mounted on the burner box is open, indicating an overheating
condition in the burner. Check for a blocked vent or an overfired condi-
tion.
7 Red Flashes: Indicates a gas valve short circuit. The control board
has sensed that the gas valve circuit is shorted. Check for miswiring of
the gas valve or a shorted gas valve wire.
1 Amber Flash: Indicates low flame current. The flame current being
sensed by the flame sensor has dropped below the normal level. The
furnace continues to operate in this condition, but if the flame current
continues to drop, the burners shut down. Check for a dirty flame sen-
sor.
2 Amber Flashes: Indicates ID plug failure. The furnace is equipped
with an ID plug on the control board that is used to transmit model-spe-
cific information to the board. If this error occurs, it means that the con-
trol is unable to detect the ID plug. The furnace does not operate
correctly without the correct ID plug installed.
3 Amber Flashes: Indicates the control fuse is open. The low-voltage
fuse on the control board has opened or is missing.
Rapid Red Flashes: Indicates incorrect line voltage polarity. The polar-
ity of the incoming power to the furnace is reversed.
Soft Lockout: The control includes a soft lockout that resets automati-
cally after 1 h. This provides protection to an unoccupied structure if a
temporary condition causes a furnace malfunction, for example, if a
temporary interruption in gas supply prevents the furnace from lighting.
The control keeps trying to light each hour and resumes normal opera-
tion if the gas supply is restored.
Hard Lockout: Some fault conditions result in a hard lockout, and you
must turn off the power to the control and turn on the power to the con-
trol again to reset the control. The control does not automatically
restart.
DIAGNOSTIC FAULT CODE STORAGE AND
RETRIEVAL
The control in the furnace is equipped with memory that stores up to
five error codes to allow a service technician to diagnose problems
more easily. This memory is retained even if power to the furnace is
lost.
Note: This feature must only be used by a qualified service technician.
If more than five error codes have occurred since the last reset, only the
five most recent are retained. The furnace control board has an SW but-
ton that is used to retrieve error codes. This function only works if there
are no active thermostat signals, so any call for heating, cooling, or con-
tinuous fan must be terminated before attempting to retrieve error
codes.
To retrieve the error codes, press the SW button. The LED on the con-
trol flashes the error codes that are in memory, starting with the most
recent. There is a 2-s pause between each flash code. After the error
codes have all been displayed, the LED resumes the normal slow green
flash after a 5-s pause. To repeat the series of error codes, press the
SW button again.
If there are no error codes in memory, the LED flashes two green
flashes. To clear the memory, press and hold the SW button for more
than 5 s. The LED flashes three green flashes when the memory has
been cleared, then resumes the normal slow green flash after a 5-s
pause.
IGNITION CONTROL FLAME SENSE LEVELS
Normal flame sense current range: 3–10 microamps
Low flame signal warning starts at 3.0 microamps
Low flame sense lockout point: 1.0 microamps
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