Lennox Mini Split F6 Error Code

Updated 2026-08-30 · review status: manual-verified · reviewed by MiniSplitDecoder Editorial Team Last verified: 2026-08-30

Check your model first

  • Lennox (Service Manual 100030, Section 6.15, F6/EC 56)
  • Lennox 3WMC Table 1 (outdoor display form)
  • Midea-built platform (MRCOOL DIY 4 manual sensor group)

Match the model on your equipment label to the linked manufacturer documentation. The same code can mean different things across model families.

Quick answer

F6 on Lennox mini splits (indoor display; outdoor equivalent EC 56) means the evaporator coil outlet temperature sensor (T2B) is in open circuit or short circuited - the thermistor circuit is broken or reading outside its allowed window (below 0.06 V or above 4.94 V), so the control stops the system. Power cycle once; if F6 returns, the sensor circuit needs technician service.

Severity: medium · DIY difficulty: easy

Safety

Stop at the breaker power-cycle and any plug-accessible checks (filters, remote settings, visible wiring). The outdoor unit's capacitor holds a lethal charge and the refrigerant circuit is both pressurized and (on R-32 units) flammable — opening panels or servicing the sealed system is licensed-technician work (EPA 608).

What F6 means

F6 on Lennox mini splits (indoor display; outdoor equivalent EC 56) means the evaporator coil outlet temperature sensor (T2B) is in open circuit or short circuited - the thermistor circuit is broken or reading outside its allowed window (below 0.06 V or above 4.94 V), so the control stops the system. Power cycle once; if F6 returns, the sensor circuit needs technician service.

Code meaning varies by series

  • Lennox (Service Manual 100030, Section 6.15, F6/EC 56): F6 (indoor display) = evaporator coil outlet temperature sensor T2B error (open/short circuit)
  • Lennox 3WMC Table 1 (outdoor display form): Same fault displays as EC 56 (T2B multi-zone free-match indoor units)
  • Midea-built platform (MRCOOL DIY 4 manual sensor group): T2B belongs to the platform's open/short temperature-sensor family with the same remediation

First checks before service

This page currently documents the safe reset triage. If the code returns, use the linked source manual or a qualified technician for code-specific diagnosis.

  1. 1. One-time fault event (power disturbance or transient sensor reading) common DIY

    Check: Power-cycle at the breaker/disconnect (or unplug for CPAP), restore, and run the system while watching for the code.

    Fix: If the code does not return after a full run cycle, the fault was transient — monitor, no repair needed.

  2. 2. Fault persists after a clean reset occasional pro only

    Check: If the code returns immediately or every session, note the conditions (startup, heating, after rain).

    Fix: A persisting code points at the component the manual assigns to this code — that repair is technician territory.

Related codes

Cross-references for the same fault family, by brand:

Lennox EC56 · Lennox F2 · Lennox F3 · Lennox F5 · Lennox EC54 · Lennox EC07

Commonly searched as: "lennox f6" · "lennox error code f6" · "lennox air conditioner f6"

Sources

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