FieldBench

Daikin

DX16TC

AC · Two-stage condensing unit · 16 SEER class

Daikin two-stage air conditioner (DX16TC / DX18TC). Y1/Y2 or communicating indoor depending on vintage. Not the FIT inverter and not DX13SA single-stage.

Not DC9VS / DX17VSS FIT inverter. Not DX13SA / DC5SE single-stage. Not DZ14 heat pump.

Walk this in Diagnose

This plate

Stages
Two-stage scroll · Y1/Y2
Refrigerant
R-410A on this generation

This board

Two-stage outdoor — not the FIT drive

  • High stage is Y2 unless this vintage is on the data pair.
  • No inverter U-codes. Those are DC9VS.

Sequence

  1. Y1 / low. Outdoor starts low capacity. Indoor blower on low/mid Cool tap (24V) or communicating CFM (ComfortBridge indoor).
  2. Y2 / high. Second stage. Head and subcooling should rise into the OEM SC window.
  3. Communicating pair. GMVC96 / AVPTC indoor requests capacity on the data pair. No conventional Y needed. A 24V GR9T96 on that same pair is a miswire.

Faults on this IFC

  • HPS

    High pressure

    lockout

    Outdoor airflow, overcharge, or restriction opened the high-pressure switch.

    • Outdoor fan running? Coil dirty, recirc, bent fins.
    • Subcooling vs indoor TXV sheet. Liquid-line drier / restriction.
    • Do not keep resetting HPS into a locked fan.
  • LPS

    Low pressure / freeze

    lockout

    Suction dropped out — charge, indoor airflow, or TXV.

    • Indoor filter, blower, coil freeze. Do not add gas on a frozen coil.
    • TXV / restriction. Weigh-out if the history is a leak.
    • Low ambient and wind can nuisance-trip LPS on a light load — still prove charge.
  • Comm

    Indoor/outdoor data

    lockout

    ComfortBridge data pair only. Invalid as a diagnosis on a 24V Y1/Y2 hookup.

    • Data pair polarity and splices. This is not 24V Y.
    • Indoor IFC family must be GMVC / AVPTC communicating. GR9T96 / GMEC96 / GMSS96 cannot be the ComfortBridge indoor.
    • One master on the bus. Outdoor board power before you condemn the indoor IFC.

Workflows

DX16TC stuck on low

Y2 never arrives.

  1. Prove Y2 at the outdoor.
  2. SC on the TXV indoor.
  3. FIT inverter is DC9VS — different chart.

Test points

Charge
Nameplate + line-set adders. SC per indoor TXV sheet.
Y1 / Y2
24V pair: both present on high stage. Communicating pair: data, not 24 VAC.
Outdoor board
LED/display before the disconnect. Codes die when you pull power.

Gotchas

  • DX16TV is a two-stage cousin. FIT is the inverter.

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