FieldBench
Lennox codes

Lennox

E105

Lockout

RS BUS communication

Device off the iComfort bus. Native, expected, first-class on SLP99.

Walk E105 in Diagnose

4 plates — walk the one on the cabinet

First check

1 Data pair, not 24 V

On Lennox EL195NE indoor/outdoor comm is a data pair (AB, S1/S2, U, ComfortBridge, ComfortLink — whatever THIS plate uses). It is not a 24 V Y. Check polarity, continuity, and that nobody landed it on R/C. Only if iComfort is actually wired — i+/i− polarity, one communicating control, indoor/outdoor on the bus.

Expect: Pair continuous, not shorted to chassis, polarity per the diagram.

The rest of the walkthrough is Diagnose.

On the plates

  • Only if iComfort is actually wired — i+/i− polarity, one communicating control, indoor/outdoor on the bus.
  • Many EL296V jobs are 24V. E105 on a 24V-only install means data wires landed on the RS terminals. Pull them.
  • i+/i− polarity, one communicating control, indoor and outdoor on the bus. Data, not 24 VAC.
  • Do not convert to 24V. Isolating devices one at a time finds the bad node.

Plates that use E105