Emerson 50A55 User Manual 2
TROUBLESHOOTING
WARNING
!
WARNING
!
GUIDE
Failure to read and follow all
instructions carefully before installing or operating this control,
could cause personal injury and/
or property damage.
INTEGRATED FURNACE
CONTROL MODULE
50A55 INTEGRATED FURNACE CONTROL MODULE
Qualied Serviceman’s Troubleshooting Guide
TROUBLESHOOTING PROCEDURE
If the light on the module is on continuously, the fault is likely to be internal to the
module. To make sure, interrupt line or 24 volt thermostat power for a few seconds
and then restore. If internal fault is indicated again, and ame sensor is not shorted
to ground, replace control. A ashing light indicates the problem is most likely in the
external components or wiring. Proceed as follows:
Turn power off before any troubleshooting or servicing begins.
Line voltage (120 VAC) could be present on the surface of the ignitor, if the system is not correctly wired. Such voltage can cause serious injury or death.
The following steps must be performed rst before any troubleshooting begins.
1) Disconnect electric power to system at main fuse or circuit breaker.
2) Visually inspect equipment for apparent damage. Check wiring for loose
connections.
3) Check for proper grounding and reversed polarity.
A. Check continuity for C terminal on module to electrical service ground and
connection at the furnace junction box. If ground connection is open, check
module ground connection and the electrical service ground connection.
Repair and retest.
B. Re-connect electric power to system.
C. Check for voltage between the line neutral terminal and furnace ground. If
voltage exists, the main power supply lines are improperly connected to the
furnace (REVERSED POLARITY). Again disconnect electric power to system;
then reverse incoming supply leads to furnace. Repeat step.
D. Recheck system for proper operation.
If neither apparent damage, loose connection nor reversed polarity is the problem,
proceed to troubleshooting chart or fault index chart that is suggested by the actual
condition.
NOTE: This troubleshooting guide is not for 50A55-4XX modules found on Trane
equipment or 50A55-1XX modules found on Lennox equipment.
FAULT INDEX CHART
No manual fan ............................................ 1A - 1K
Power supply and voltage .......................... 1C - 1G
No fan at cooling speed .............................. 2A - 2L
No induced draft motor ............................... 3A - 3H
LED ashing 2X without inducer................. 3E
LED ashing 3X with inducer...................... 3I - 3O
Ignitor does not glow .................................. 4A - 4D
Burner does not stay lit ............................... 4E - 4N
Gas supply problem.................................... 4F - 4K
No outlet pressure ...................................... 4H - 4J
Gas valve does not energize ...................... 4L - 4N
Flame sensor fault ...................................... 5A - 5P
Burner ground............................................. 5K
Polarity check ............................................. 5L - 5M
Ignitor stays on after burner ignition ........... 5B - 5C
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TECHNICAL HELPTECHNICAL HELP
259
Place
thermostat
fan switch in
the ON
position.
Return fan
switch to
AUTO position.
Indoor Blower
Check
Does indoor
blower run at
HEAT speed?
YES
YES
NO
NO
YES
NO
YES
NO
YES
NO
Indoor blower
fault. Repair or
replace. Check
operation.
Is 24V
present at
control
terminals
G & C?
Is 120V
present at
control terminals
COOL & CIR
NEUTRAL?
Is 24V
present at
control
terminals
R & C?
Does LED
flash 1 time
when disconnect
is turned
ON?
Is 120V
present across
primary of control
transformer?
Is 24V
present across
secondary of
transformer?
Is 24V
present
across 12-pin
connector pins TH
& TR on the
control?
Is 120V
present at
control terminals
XFMR & XFMR
NEUTRAL?
Is 120V
present across
control terminals
LINE & LINE
NEUTRAL?
Repair wiring
from control to
thermostat. Check
operation.
Repair wiring
and/or plug
connection. Check
operation.
Replace
transformer. Check
operation.
Repair wiring to
transformer. Check
operation.
Correct 120V
power supply. Check
operation.
Replace control.
Check operation.
Replace control.
Check operation.
1A 1B
1E1D1C 1F
1I1H1G 1J 1K
YES
NO
YES
NO
YES
NO
YES
NO
YES
NO
WARNING
!
INTEGRATED FURNACE
CONTROL MODULE
CHART 1
TROUBLESHOOTING
GUIDE
TECHNICAL HELP
If diagnostic indicator (LED)
shows continuous flashing, turn
off gas supply at source before
disconnecting electrical power!
260
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