Model reference

Lennox G50UH-36A-070

Furnace

1 document12 error codes1 service mode

Available documentation

Service Manual

G50UH Series Service Literature43 pg
Covers this model

MyPros+ Max

Diagnose your Lennox G50UH-36A-070.

Step-by-step diagnostics from the service manual
Test values, resistance specs, and wiring references
Verified part numbers when replacement is needed

Start diagnosing

$29/month · Cancel anytime · Or $9.95 3-day pass

M+

M+ Max·Lennox Furnace

LED1 Alternating Fast Flash / LED2 Alternating Fast Flash on my Lennox G50UH-36A-070

M+

Sensed during ignitor warm-up period

From Service Manual 736516, p.48:

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 (12)

CodeMeaning

LED1 Alternating Fast Flash / LED2 Alternating Fast FlashSensed during ignitor warm-up period only LED1 Alternating Slow Flash / LED2 Alternating Slow FlashWatchguard LED1 Fast Flash / LED2 Fast FlashNormal operation signaled when heating demand initiated at thermostat.LED1 Fast Flash / LED2 Slow FlashMain power polarity reversed LED1 Off / LED2 Slow FlashProve switch open, or blocked inlet/exhaust vent, or prove switch closed prior…LED1 On / LED2 OffCircuit board failure or control wired incorrectly.LED1 On / LED2 OnCircuit board failure or control wired incorrectly.LED1 On / LED2 Slow FlashRollout switch open, or 9-pin connector improperly attached.LED1 Slow Flash / LED2 Fast FlashLow flame signal; measures below normal threshold LED1 Slow Flash / LED2 OffFlame sensed without gas valve energized.LED1 Slow Flash / LED2 OnPrimary or secondary limit switch open; limit must close within 3 minutes or…LED1 Slow Flash / LED2 Slow FlashPower on, normal operation; also signaled during cooling and continuous fan.

Service modes (1)

SureLight Diagnostic LED MonitoringUpon initial power up, remove all thermostat demands to the unit

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

Related Lennox furnace models

78,000+ service manuals · 160,000+ error codes · 55+ brands

$29/month · Cancel anytime · Or $9.95 3-day pass