Lennox Ducted Heating

Lennox Error Code FAST FLASH, SLOW FLASH

Ducted Heating:

What It Means

  • Main power polarity reversed. Switch line and neutral.

Causes & actions from Lennox

How it shows
  • SureLight board LEDs (DS1/DS2): FAST FLASH, SLOW FLASH (led1: flashing (fast), led2: flashing (slow))
  • SureLight board LEDs (DS1/DS2): FAST FLASH, SLOW FLASH (led1: flashing (fast), led2: flashing (slow))
  • SureLight board LEDs (DS1/DS2): FAST FLASH, SLOW FLASH (led1: flashing (fast), led2: flashing (slow))

This manual entry does not list further causes or actions.

Applicable models & manual sources
Disclaimer: This information is for general reference. Code wording and instructions vary by model. Always follow the service manual for your exact unit.

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