437642-UIM-C-0210
Johnson Controls Unitary Products
25
TROUBLESHOOTING
The following visual checks should be made before troubleshooting:
1.
Check to see that the power to the furnace and the ignition control
module is ON.
2.
The manual shut-off valves in the gas line to the furnace must be
open.
3.
Make sure all wiring connections are secure.
4.
Review the sequence of operation. Start the system by setting the
thermostat above the room temperature. Observe the system’s
response. Then use the troubleshooting section in this manual to
check the system’s operation.
FURNACE CONTROL DIAGNOSTICS
The furnace has built-in, self-diagnostic capability. If a system problem
occurs, a blinking LED 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 will indicate the failure code. If
the failure is internal to the control, the light will stay on continuously. In
this case, the entire control should be replaced, as the control is not
field repairable.
Flash sequence codes 1 through 12 are as follows: LED will turn “on”
for 1/4 second and “off” for 1/4 second. This pattern will be repeated the
number of times equal to the code. For example, six “ON” flashes
equals a number 6 fault code. All flash code sequences are broken by a
2 second “OFF” period.
SLOW GREEN FLASH:
Normal operation.
SLOW AMBER FLASH:
Normal operation with call for heat.
RAPID RED FLASH:
Twinning error, incorrect 24V phasing. Check
twinning wiring.
RAPID AMBER FLASH:
Flame sense current is below 1.5 microamps.
Check and clean flame sensor. Check for proper gas flow. Verify that
current is greater than 1.5 microamps at flame current test pad.
4
AMBER FLASHES:
The control is receiving a “Y” signal from the
thermostat without a “G” signal, indicating improper thermostat wiring.
1 RED FLASH:
This indicates that flame was sensed when there was
not a call for heat. The control will turn on both the inducer motor and
supply air blower. A gas valve that leaks or is slow closing would typi-
cally cause this fault.
2 RED FLASHES:
This indicates that the normally open pressure
switch contacts are stuck in the closed position. The control confirms
these contacts are open at the beginning of each heat cycle. This would
indicate a faulty pressure switch or miswiring.
3 RED FLASHES:
This indicates the normally open pressure switch
contact did not close after the inducer was energized. This could be
caused by a number of problems: faulty inducer, blocked vent pipe, bro-
ken pressure switch hose or faulty pressure switch.
4 RED FLASHES:
This indicates that the main limit switch has opened
its normally closed contacts. The control will operate the supply air
blower and inducer. This condition may be caused by: dirty filter,
improperly sized duct system, incorrect blower speed setting, incorrect
firing rate or faulty blower motor. Also, this fault code could be caused
by a blown fuse located on the control board.
5 RED FLASHES:
This fault is indicated if the normally closed contacts
in the rollout switch opens. The rollout control is manually reset. If it has
opened, check for proper combustion air, proper inducer operation, and
primary heat exchanger failure or burner problem. Be sure to reset the
switch and cycle power (24VAC) to the control after correcting the fail-
ure condition. Also, this fault code could be caused by a blown fuse
located on the control board.
6 RED FLASHES:
This indicates that after the unit was operating, the
pressure switch opened 4 times during the call for heat. If the main
blower is in a “Delay on” mode, it will complete it, and any subsequent
delay off period. The furnace will lock out for one hour and then restart.
7 RED FLASHES:
This fault code indicates that the flame could not be
established. This no-light condition occurred 3 times (2 retries) during
the call for heat before locking out. Low gas pressure, faulty gas valve,
dirty or faulty flame sensor, faulty hot surface ignitor or burner problem
may cause this. The furnace will lock out for one hour and then restart.
8 RED FLASHES:
This fault is indicated if the flame is lost 5 times (4
recycles) during the heating cycle. This could be caused by low gas
pressure, dirty or faulty flame sensor or faulty gas valve. The furnace
will lock out for one hour and then restart.
9 RED FLASHES:
Indicates reversed line voltage polarity or grounding
problem. Both heating and cooling operations will be affected. Check
polarity at furnace and branch. Check furnace grounding. Check that
flame probe is not shorted to chassis.
10 RED FLASHES:
Flame sensed with no call for heat. Check gas
valve and gas valve wiring.
11 RED FLASHES:
This indicates that a primary or auxiliary limit switch
has opened its normally-closed contacts and has remained open for
more than five minutes. This condition is usually caused by a failed
blower motor or blower wheel. Cycle power (24VAC) to the control to
reset the hard lockout condition after correcting the failure condition.
Never bypass any safety control to allow furnace operation. To do
so will allow furnace to operate under potentially hazardous condi-
tions.
Do not try to repair controls. Replace defective controls with UPG
Source 1 Parts.
Never adjust pressure switch to allow furnace operation.
