Model reference

Lennox GHR26Q3/4-100

Furnace

1 document17 error codes2 service modes

Available documentation

Service Manual

GHR26 SERIES UNITS Service Literature47 pg
Covers this model

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M+ Max·Lennox Furnace

DIAG#1: Alternate Flash / DIAG#2: Alternate Flash on my Lennox GHR26Q3/4-100

M+

Watchguard — burners failed to ignite.

From Service Manual 804994, p.46:

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 (17)

CodeMeaning

DIAG#1: Alternate Flash / DIAG#2: Alternate FlashWatchguard DIAG#1: Continuous On / DIAG#2: Continuous OnCircuit board self-check failure or ignition/blower control is wired…DIAG#1: Flash / DIAG#2: OffPressure switch Watchguard DIAG#1: Off / DIAG#2: FlashFlame sensed without gas valve energized.DIAG#1: On / DIAG#2: FlashPrimary or secondary limit switch open (auto-reset switch).DIAG#1: Simultaneous Flash / DIAG#2: Simultaneous FlashPower ON, normal operation; increased flash rate indicates a heating demand.LED#1: Alternating Fast Flash / LED#2: Alternating Fast FlashImproper main ground or line voltage below 75 volts; or broken ignitor; or open…LED#1: Alternating Slow Flash / LED#2: Alternating Slow FlashWatchguard LED#1: Fast Flash / LED#2: Slow FlashMain power polarity reversed LED#1: Off / LED#2: OnCircuit board failure or control wired incorrectly.LED#1: Off / LED#2: Slow FlashPressure switch open or has opened 5 times during a single call for heat; or…LED#1: On / LED#2: OffCircuit board failure or control wired incorrectly.LED#1: On / LED#2: OnCircuit board failure or control wired incorrectly.LED#1: On / LED#2: Slow FlashRollout switch open or 9-pin connector improperly attached.LED#1: Slow Flash / LED#2: Fast FlashLow flame signal LED#1: Slow Flash / LED#2: OffFlame sensed without gas valve energized.LED#1: Slow Flash / LED#2: OnPrimary or secondary limit open; limit must close within specified trials/time…

Service modes (2)

EGC-1 Diagnostic Memory Recall["Restore power to control (depress blower interlock switch) within one minute of blower access…
Lennox Diagnostic Module Connection["Connect Lennox Diagnostic Module (part number 11K75) to the slotted edge connector on the EGC-1…

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