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KB Home / Equipment / Gas Furnaces / Lennox/Ducane / G51MP / G51MP Fault Codes/Diagnostic Codes

G51MP Fault Codes/Diagnostic Codes

Article ID: 736
Last updated: 28 Dec, 2023

Nordyne Gas Furnace: G51MP

Re: Furnace Lockout Codes

Furnace Control Board Fault Conditions

DS1

(Red or Green)

DS2

(Green)

 Description
Simultaneous Slow Flash Power On - No Call For Heat
Simultaneous Fast Flash Normal Operation - Call For Heat
Slow Flash On Primary or secondary limit switch open. Limit must close within 3 minutes or unit goes into
1−hour Watchguard.
Off Slow Flash Pressure Switch Fault: Open with inducer on or Closed with inducer off.
Alternating Slow Flash Watchguard −− Burners failed to ignite, limit open longer than 3 minutes, or flame sense lost 5
times in one heating cycle.
Slow Flash Off Flame sensed without gas valve energized.
On Slow Flash Rollout switch open.
On On

Control Board Failure or Control Mis-Wired.  Check 24V and 115V Wiring Connections.
Off On
On Off
Fast Flash Slow Flash Main power polarity reversed. Switch line and neutral. Improper main ground.
Slow Flash Fast Flash Low flame signal. Check flame sensor.
Alternating Fast Flash The following conditions are sensed during the ignitor warm−up period only:
1) Improper main ground;
2) Broken ignitor; OR: Open ignitor circuit;
3) Line voltage below 75 volts.
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Article ID: 736
Last updated: 28 Dec, 2023
Revision: 5
Access: Public
Views: 130
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