Troubleshooting Procedures - American Standard *UD Series Operation Manual

White-Rodgers Troubleshooting Procedures
Furnace Models 50A50 and 50A51
f the light on the module is on continuously, the fault is
I
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
flame sensor is not shorted to ground, replace control. A
flashing light indicates the problem is most likely in the
external components or wiring. Proceed as follows:
Line voltage (120V AC) 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 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 from B/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 electrical power to the system
C. Check for voltage between the line neutral
terminal and furnace ground. If voltage exists, the
main power supply lines are improperly con-
nected 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 or
fault index chart that is suggested by the actual condition,
see below.
CAUTION:
If diagnostic indicator (LED) shows five
(5) flashes, turn off gas supply at source before discon-
necting electrical power. Failure to do so may result in
personal injury or fire.
Furnace Model 50A52
The following stops must be performed before any trouble-
shooting begins on any Radiant Sense Furnace model:
1. Disconnect electric power to system at main fuse or
circuit breaker.
2. Visually inspect equipment for appar ent damage.
Check wiring for loose connections.
3. Check for proper unit grounding.
4. Check for broken ignitor.
5. Visually inspect pressure switch hose for cracks, splits
and tight connection to the barbed fitting.
6. Inspect vent pipe for signs of corrosion or condensation.
7. Re-connect power to system.
8. Check system operation.
If problem is found, refer to the fault index chart for that
particular problem or proceed directly to the trouble-
shooting chart.
50A50 Fault Chart
Probable Fault
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 flashing slowly .............................................. 3B-3C
LED on continuously ................................................. 1G
LED flashing 3 X without inducer .............................. 3E
LED flashing 3 X 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
50A51 Fault Chart
Probable Fault
No manual fan ........................................................... 1A
Power supply and voltage ......................................... 1B
No low heat fan ......................................................... 2A
No induced draft motor ............................................. 2B
LED flashing slowly .................................................... 2C
LED on continuously ................................................. 2D
LED flashing 3 X without inducer .............................. 2E
LED flashing 3 X with inducer .................................. 3A
Ignitor does not glow ................................................. 3B
Gas supply problem ................................................... 3C
No outlet pressure ..................................................... 3D
Gas valve does not energize ...................................... 3E
Flame sensor fault ..................................................... 4A
Burner ground ............................................................ 4B
Polaritycheck ............................................................... 4C
Ignitor stays on after burner ignition ....................... 4D
Indoor does not shift to high speed ......................... 5A
Gas valve does not switch to high heat .................... 5B
Indoor blower does not switch to high speed .......... 5C
50A52 Fault Chart
Probable Fault
No cooling fan operation .......................................... 1A
No 24 volt secondary voltage .................................... 1B
Induced Draft Motor inoperative .............................. 2A
Defective pressure switch .......................................... 2B
Ignitor won't glow ................................................ 2B-3A
Gas valve does not open ............................................ 3B
Radiant flame sensor ................................................ 4A
No heating fan operation ........................................... 4B
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