1083293-UIM-D-1116
Johnson Controls Unitary Products
39
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
This furnace has built-in self-diagnostic capability. If a system problem
occurs, a flashing LED shows a fault code. The LED can flash red,
green or amber to indicate various conditions. The LED is located on
the furnace control board and can be seen through the clear view port
in the lower door of the furnace. To indicate an error condition, the LED
will turn on for 1/4 second and off for 1/4 second. The pattern will be
repeated the number of times equal to the flash code. For instance, a
“six flash code” will be indicated by the LED turning on and off six times.
There will be a two second off period between each set of flashes. The
flash codes and an indication of their likely causes are listed below:
STEADY OFF -
No 24V power to board. Check the 24 volt control cir-
cuit fuse on the board. Check the circuit breaker or fuse on the 115 volt
supply power to the furnace. Check that the 24 volt transformer.
One Green Flash -
Normal Operation with no call for heat.
Two Green Flashes -
Indicator for
“
No error codes in memory
”
. See
Diagnostic Fault Code Storage and Retrieval section below.
Three Green Flashes -
Indicator for
“
Error codes cleared from mem-
ory”. See Diagnostic Fault Code Storage and Retrieval section below.
Rapid Green Flash -
Control is in
“
Factory Speed-up
”
mode. This
mode is used only during factory run-testing of the furnace. To stop this
mode, cycle power to the furnace off and then back on.
One Amber Flash -
Normal operation with call for cooling.
Two Amber Flashes -
Normal operation with call for heat.
Three Amber flashes -
Normal operation, burner is on at end of heat-
ing cycle after wall thermostat has been satisfied.
Four Amber Flashes -
Heating capacity is reduced due to restriction in
the circulating air system. Check for dirty filter or closed registers.
Five Amber Flashes -
Heating capacity is reduced due to restriction in
the combustion air or vent system. Check for blocked vent/air pipe or
clogged condensate drain. Above 4,000 feet altitude, this may also indi-
cate automatic, normal derating for altitude. See page 7 for additional
high altitude information.
Six Amber Flashes -
(Heat Pump applications only) Normal operation
with call for heat pump heating.
Rapid Amber Flash -
Low flame sense current. Check for dirty or mis-
located flame sensor rod.
One Red Flash -
Flame is present with no power being supplied to gas
valve. This can be caused by a gas valve that is slow to close or that
leaks gas through to the burners.
Two Red Flashes -
Pressure switch closed with inducer pressure
below pressure switch setpoint (switch is closed when it should be
open). Check pressure switch and pressure transducer.
Three Red Flashes -
Pressure switch open with inducer pressure
above pressure switch setpoint (switch is open when it should be
closed). Check pressure switch and pressure transducer.
Four Red Flashes -
This indicates that a primary or auxiliary limit
switch has opened its normally closed contacts. With this fault code 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. This
fault can also be the result of a blown fuse located on the circuit board.
Five Red Flashes -
This fault is indicated if the normally closed con-
tacts in the rollout switch opens. The rollout control is manually reset. If
it has opened, check for proper combustion air, proper inducer opera-
tion, and primary heat exchanger failure or burner problem. Be sure to
reset the switch after correcting the failure condition. This fault can also
be the result of a blown fuse located on the circuit board.
Six Red Flashes -
Gas valve communication error - Check wiring from
board to gas valve. Check air pressure sensor connections. Check
pressure switch hoses and connections.
Seven Red Flashes -
Lockout due to no ignition. The control will try
three times for ignition. If flame cannot be established in three tries, the
control will lockout for one hour and then will try again to light. Check
gas supply, ignitor, gas valve, flame sensor.
Eight Red Flashes -
Lockout due to too many flame recycles. This
flash code occurs if flame is lost five times during a single heating cycle.
This could be caused by a faulty gas valve, low gas pressure, or dirty
flame sensor. The control will lock out for one hour and then will try
again.
Nine Red Flashes -
Reversed line polarity or improper grounding.
Check polarity of the incoming power to the furnace. Check the ground-
ing of the furnace, including the transformer ground and the L1 and
neutral connections.
Ten Red Flashes -
Gas valve circuit shorted. Check gas valve wiring. If
correct, replace gas valve.
Eleven Red Flashes -
Main blower failure - This flash code occurs
when the main limit opens and fails to reclose within five minutes, indi-
cating that the blower motor or blower wheel has failed.
Twelve Red Flashes -
ID plug is not present or not connected properly,
check for loose plug or loose wires in plug.
Steady On Red -
Control fault has been detected or there is 115 volts
present without 24 volts. Check whether there is 24 volts and 115 volts
being supplied to the board. If not, correct the voltage problem. If there
is both 24 and 115 voltage to the board, replace the control board.
WARNING
Never bypass any safety control to allow furnace operation. To
do so will allow 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.
!
IGNITION CONTROL FLAME SENSE LEVELS
Normal flame sense current is approximately
3.7 microamps DC (
μ
a)
Low flame signal warning starts at 1.5 microamps.
Low flame signal control lockout point is
0.1 microamps DC (
μ
a)
