WARNING
Never bypass any safety control to allow
furnace operation. To do so allows furnace
to operate under potentially hazardous
conditions.
Do not try to repair controls. Replace defective
controls with UPG Source 1 Parts.
Never adjust pressure switch to allow furnace
operation.
Furnace control diagnostics
The furnace has built-in, self-diagnostic capability. A
blinking LED light on the control board can flash red,
green or amber to indicate various conditions. The
control continuously monitors its own operation and the
operation of the system. If a failure occurs, the LED light
indicates the failure code.
The SLOW flash speed is 2 s on and 2 s off.
The other flash codes listed below have the following
timing: LED light turns on for 1/3 s and off for 1/3 s. This
pattern is repeated the number of times equal to the
code. There is a 2 s pause between codes. For example,
the six red flash code flashes the LED light on and off six
times, then is off for 2 s. This pattern repeats as long as
the fault condition remains.
SLOW GREEN FLASH: Normal operation, no thermostat
calls.
SLOW AMBER FLASH: Normal operation with call for heat.
LED STEADY OFF – If the LED light does not flash at all,
check for power to the control board and check for an
open fuse on the control board. If the control board is
adequately powered and the fuse is not open, the control
board may need to be replaced.
STEADY ON ANY COLOR: Possible control failure. Turn
power to the furnace off and back on. If the fault code
returns, the control board must be replaced. The control
board is not field-repairable.
RAPID AMBER FLASH: This indicates low flame sense
current.
ALTERNATING RED AND AMBER FLASH: This indicates a
refrigerant leak detected near the furnace.
1 RED FLASH: This indicates that flame was sensed when
there was not a call for heat. The control turns on both the
inducer motor and supply air blower. Check for a leaking
or slow-closing gas valve.
2 RED FLASHES: This indicates that the pressure switch is
closed when it should be open. The control confirms that
the pressure switch contacts are open at the beginning
of each heat cycle and does not let the ignition sequence
continue if the pressure switch contacts are closed when
they should be open. Check for a faulty pressure switch or
miswiring.
3 RED FLASHES: This indicates the pressure switch
contacts are open when they should be closed. Check for
faulty inducer, blocked vent pipe, broken pressure switch
hose, disconnected pressure switch or inducer wires or
faulty pressure switch.
4 RED FLASHES: This indicates that 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 a dirty filter, incorrectly
sized duct system, incorrect blower speed setting,
incorrect firing rate, loose limit switch wiring or faulty
blower motor.
If the limit switch has not closed within 5 min, the control
assumes that the blower is not functioning, starts a hard
lockout and begins to flash the 11 Red Flashes error code.
Power has to be cycled off and on to reset the control
after the problem has been corrected. See the 11 Red
Flashes description below.
If the main limit switch opens five times within a single
call for heat, the control also indicates 4 Red Flashes and
enters a one-hour soft lockout.
5 RED FLASHES: This fault is indicated if the normally
closed rollout switch opens or if the limit switch has been
open longer than 15 min. The rollout control is manually
reset. Check for adequate combustion air, correct inducer
operation, and primary heat exchanger failure or burner
problem. The control enters a hard lockout and power
has to be cycled off and on to reset the control after the
problem has been corrected.
6 RED FLASHES: This indicates that while the unit was
operating, the pressure switch opened four times during
the call for heat. Check for faulty inducer, blocked vent
pipe or faulty pressure switch. The furnace locks out for 1
h and then restarts.
7 RED FLASHES: This fault code indicates that the flame
could not be established during three trials for ignition.
Check that the gas valve switch is in the ON position.
Check for low or no gas pressure, faulty gas valve, dirty or
faulty flame sensor, faulty hot surface ignitor, loose wires
or a burner problem. The furnace locks out for 1 h and
then restarts.
8 RED FLASHES: This fault is indicated if the flame is lost
five times (four recycles) during the heating cycle. Check
for low gas pressure, dirty or faulty flame sensor or faulty
gas valve. The furnace locks out for 1 h and then restarts.
9 RED FLASHES: Indicates reversed line voltage polarity,
grounding problem or reversed low voltage transformer
wires. Both heating and cooling operations are affected.
Check polarity at furnace and branch. Check furnace
grounding. Check that flame probe is not shorted to
chassis. The furnace does not start the ignition sequence
until this problem is corrected.
10 RED FLASHES: Gas valve energized with no call for
heat. The main blower and inducer blower run and no
ignition sequence is started as long as this condition
exists. Check gas valve and gas valve wiring.
11 RED FLASHES: This indicates that the main limit
switch has opened its normally-closed contacts and has
remained open for more than 5 min. This condition is
usually caused by a failed blower motor or blower wheel.
The control enters a hard lockout and power has to be
cycled off and on to reset the control after the problem
has been corrected.
Installation Manual: RL18 Single-Stage Standard ECM Residential Gas Furnaces (Non-condensing Multi-position Standard
Low NOx)
36
Johnson Controls Ducted Systems
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