Lennox Split & Multi-Split

Lennox Error Code Simultaneous FAST Flash

Split & Multi-Split:

What It Means

  • Ambient Sensor Problem

Causes & actions from Lennox

How it shows
  • defrost control ds2 ds1 led: Simultaneous FAST Flash (ds1: flashing (fast), ds2: flashing (fast))
  • defrost control ds2 ds1 led: Simultaneous FAST Flash (ds1: flashing (fast), ds2: flashing (fast))

Ambient Sensor Problem. Sensor being detected open or shorted or out of temperature range. Board will revert to time/temperature defrost operation. (System will still heat or cool).

Other manual wording

EL16XP1, ML16XP1

Sensor being detected open or shorted or out of temperature range. Demand defrost control will revert to time/temperature defrost operation. (System will still heat or cool).

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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