Model reference

Lennox SL280UH090XV48B

Furnace

1 document20 error codes3 service modes

Available documentation

Service Manual

SL280UHV(X) SERIES UNITS Service Literature52 pg
Covers this model

MyPros+ Max

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Test values, resistance specs, and wiring references
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M+

M+ Max·Lennox Furnace

1+2 on my Lennox SL280UH090XV48B

M+

Low flame signal — Check flame sensor.

From Service Manual 997631, p.43:

1.Access service mode to confirm the active fault code and read stored error history.

2.Measure control board supply voltage at test points. Expected: 12 VDC and 5 VDC.

3.Inspect all connectors on the main control for corrosion or backed-out pins.

Part WPW10804018

Electronic control board

Error codes (20)

CodeMeaning

1+2Low flame signal 1+3Flame sensed out of sequence 2+3Low fire pressure switch sensed open. 80%2+4Low fire pressure switch sensed closed prior to activation of combustion air…2+5High fire pressure switch sensed open. 80%2+6High fire pressure switch sensed closed prior to activation of combustion air…2+7Low fire pressure switch opened during ignition trial or heating demand.3+1Primary / Secondary limit switch open.4+1Watchguard 4+2Watchguard 4+3Watchguard 4+5Watchguard 4+6Watchguard 4+7Watchguard 4+8Watchguard 5+1Rollout circuit open 5+2Control failed self check, internal error (control will restart if error…5+3No earth ground (control will restart if error recovers).5+4Reversed line voltage polarity (control will restart if the error recovers).5+5Low 24V (control will restart if voltage rises to normal).

Service modes (3)

Blower Motor Isolation Test (24V checkout)["1
Clearing Error Codes["1
Error Code Review["1

Full entry steps, exit procedures, and test sequences are available in Max.

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