Model reference
Lennox F8AUHX
Furnace
1 document13 error codes1 service mode
Available documentation
Service Manual
- F8AUH Gas Furnaces Service Manual28 pg
MyPros+ Max
Diagnose your Lennox F8AUHX.
- 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 · Plus applicable tax
Error codes (13)
CodeMeaning
LED1-ALTERNATING FAST FLASH / LED2-ALTERNATING FAST FLASHImproper main ground or line voltage below 75 volts; OR broken ignitor; OR open…LED1-ALTERNATING SLOW FLASH / LED2-ALTERNATING SLOW FLASHWatchguard modeLED1-FAST FLASH / LED2-FAST FLASHNormal operation signaled when heating demand initiated at thermostat.LED1-FAST FLASH / LED2-SLOW FLASHMain power polarity reversedLED1-OFF / LED2-ONCircuit board failure or control wired incorrectly.LED1-OFF / LED2-SLOW FLASHPressure switch open or has opened 5 times during a single call for heat; OR…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 signalLED1-SLOW FLASH / LED2-OFFFlame sensed without gas valve energized.LED1-SLOW FLASH / LED2-ONPrimary or secondary limit open. Units with board 12L42LED1-SLOW FLASH / LED2-SLOW FLASHPower on, normal operation; also signaled during cooling and continuous fan.Service modes (1)
- Control Board Self-CheckEach time power is applied to the furnace, the control board performs a self-check including…
Full entry steps, exit procedures, and test sequences are available in Max.
Related Lennox furnace models
75,000+ service documents · 20,000+ error codes · 100+ brands
Get Started$29/month · Cancel anytime · Or $9.95 3-day pass · Plus applicable tax