FieldBench
Trane codes

Trane

Comm

Lockout

Data bus

Indoor / stat / outdoor dropped off ComfortLink. Not an S9V2 E-decimal.

Walk Comm in Diagnose

Sign in for the next measurement

First check

1 Data pair, not 24 V

On Trane XC95m 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. Data pair landing and polarity. One communicating control.

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

The rest of the walkthrough is Diagnose.

On the plates

  • Data pair landing and polarity. One communicating control.
  • No 24V on the data pins. No extra ‘common’ spliced onto the pair.
  • Isolate devices: stat only, then indoor, then outdoor. A failed XV20i drive can look like a dead furnace IFC.

Plates that use Comm

Same number, other makers

Comm on Trane is not the same code on these plates.