Mitsubishi M / MXZ · S1 S2 S3
S1 / S2 / S3
S1 / S2 / S3
M-series wall and MXZ multi-zone. S1/S2 power, S2/S3 comm on most M-series. Not Daikin P1/P2 and not 24V thermostat cable.
Written circuit description only — FieldBench does not redraw maker schematics. Example: R to W closes on a heat call; verify 24V at W1 before you change the IFC.
Open manufacturer PDFS1 / S2 / S3
Head to outdoor, or outdoor to branch box on MXZ.
Indoor head
Voltage on S1/S2 (power) vs S2/S3 (comm) per THAT outdoor diagram.
- S1PowerLine
- S2Power / comm commonLine
- S3CommData
Outdoor / branch box
Same three. Never megger the pair. Isolate heads one at a time on U4.
- S1PowerLine
- S2CommonLine
- S3CommData
Landing
- LineHead S1outdoor S1
Line / power — not 24V
- LineHead S2outdoor S2
Common
- DataHead S3outdoor S3
Comm. No 240 on this pin.
Prove it
- S1/S2 power vs S2/S3 comm per the diagram on THAT outdoor.
- U4: isolate indoors (power down first).
Do not
- Do not treat this as 24V R/C/Y.
- Do not assume Daikin P1/P2 or Carrier ABCD.
- Never megger S2/S3.
S1/S2/S3 is the published M-series / MXZ landing.