Emerson 50A55 Manuel D’Utilisation

Qualified Serviceman’s Troubleshooting Guide

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 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:

tem is not correctly wired. Such voltage can cause serious injury or death.
The following steps must be performed first 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.

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 2X without inducer.................  3E
LED flashing 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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