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364861-UIM-B-0708
Johnson Controls Unitary Products 33
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 (24 VAC) 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 (24 VAC) to the control to
reset the hard lockout condition after correcting the failure condition.
12 RED FLASHES: This code indicates an open igniter circuit, which
could be a disconnected or loose wire or a cracked or broken igniter.
STEADY ON RED: Control failure. Replace control board.
60-MINUTE AUTOMATIC RESET FROM LOCKOUT: This control
includes a “watchdog” type circuit that will reset from a lockout condition
after 60 minutes. Operational faults 6,7,8 will be reset. This provides
protection to an unoccupied structure if a temporary condition exists
causing a furnace malfunction. An example would be a low incoming
gas supply pressure preventing unit operation. When the gas pressure
is restored, at some point the “watchdog” would restart the unit and pro-
vide heat for the house.
NOTE: If a flame is detected the control flashes the LED for 1/8 of a
second and then enters a flame stabilization period.
DIAGNOSTIC FAULT CODE STORAGE AND
RETRIEVAL
The control in this furnace is equipped with memory that will store up to
five error codes to allow a service technician to diagnose problems
more easily. This memory will be retained even if power to the furnace
is lost. This feature should only be used by a qualified service tech-
nician.
If more than five error codes have occurred since the last reset, only the
five most recent will be retained. The furnace control board has a but-
ton, labeled "LAST ERROR" that is used to retrieve error codes. This
function will only work if there are no active thermostat signals. So any
call for heating, cooling or continuous fan must be terminated before
attempting to retrieve error codes.
To retrieve the error codes, push the LAST ERROR button. The LED on
the control will then flash the error codes that are in memory, starting
with the most recent. There will be a two-second pause between each
flash code. After the error codes have all been displayed, the LED will
resume the normal slow green flash after a five second pause. To
repeat the series of error codes, push the button again.
If there are no error codes in memory, the LED will flash two green
flashes. To clear the memory, push the LAST ERROR button and hold it
for more than five seconds. The LED will flash three green flashes when
the memory has been cleared, then will resume the normal slow green
flash after a five-second pause.
IGNITION CONTROL FLAME SENSE LEVELS
Normal flame sense current is approximately
3.7 microamps DC (µa)
Low flame signal warning starts at 1.5 microamps.
Low flame signal control lockout point is
0.1 microamps DC (µa)
FIGURE 41: Furnace Control Event Schedule
Thermostat Calling for Heat
Thermostat Satisfied
(Seconds)
THERMOSTAT
INDUCER
IGNITOR
MAIN VALVE
HUMIDIFIER
ELECTRONIC
AIR CLEANER
CIRCULATING
BLOWER
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON
ON
ON
ON
OFF
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
OFF
OFF
OFF
OFF
OFF
15
Sec.
Post
Purge
Fan on Delay
30 Seconds
0
2
17 22
52
0
60, 90, 120, 180 SEC.
Selectable Fan Off Delay