FieldBench
Models
Daikinheat pump

DZ20VC

Daikin communicating inverter heat pump outdoor

Daikin communicating heat-pump outdoor. DZ20VC is the inverter SKU; some siblings in the aisle are two-stage communicating (DX18TC-class) and do not use inverter L-codes the same way. Codes live on the outdoor board (U4, L5/E6, HPS, LPS). Indoor furnace codes are a different chart.

Not a single-stage GSZ14 (contactor + defrost board only). Not DX18TC two-stage communicating — that is a two-step scroll, not this inverter drive. Not a VRV branch selector. Not indoor E2/E3 on a DM96VC.

Diagnose this modelInstall notesBoard cross-refField wiring

DZ20VC

Inverter communicating HP · variable capacity · weigh-in charge

DZ18VC

Close communicating HP sibling — confirm inverter vs two-stage on THAT plate

Two-stage cousin

DX18TC / similar — Y1/Y2 or ComfortNet two-step, SC on TXV, not this L5 drive chart

Pair

Communicating air handler / DM96VC / AVPTC-class. 24V Y1/Y2 only if the outdoor supports fallback

Side-discharge

DX17VSS is a different fan path with the same comms idea — not this cabinet

This board

Outdoor inverter / communicating PCB

  • Codes are on the outdoor board, not the indoor IFC. Photograph before the disconnect — disconnect clears live.
  • U4 / comms = indoor–outdoor data. Only valid on a communicating indoor. A GR9T96 cannot clear U4 on data wire.
  • Inverter SKUs: L5 overcurrent, E6 compressor start, plus HPS/LPS. Two-stage SKUs will not speak L5 the same way — confirm the plate before you chase a drive.
  • Furnace E2 on a DM96VC is the indoor trap, not this board.

Outdoor LED/display before you pull the disconnect. Daikin One / ComfortNet events name the outdoor fault in English when the bus is alive.

Universal swap

No universal

Inverter outdoor. No furnace IFC.

White-Rodgers

—

ICM

—

Honeywell

—
  • Indoor furnace universals (50A55, 50M56U, ICM282B, ICM2811). This is not an IFC.
  • Do not ‘adapt’ a furnace board to an outdoor inverter or defrost PCB.

After you pull the dead card

  1. 1OEM Daikin outdoor inverter PCB.

Field wiring

Written landings for Daikin DZ20VC. Not a factory schematic.

Daikin FIT / ComfortNet inverter AC
P1 / P2R-410A

DC9VS / DC6VS / DX17VSS FIT. P1/P2 indoor–outdoor. DX16TC / DX13SA / DC5SE are 24V — different diagrams.

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 PDF

This indoor

ComfortNet indoor on P1/P2. Heat-pump outdoor — RV lives here.

P1 / P2

Daikin One / ComfortNet / FIT communicating indoor.

Communicating indoor

P1/P2 to the outdoor. Not S1/S2/S3 Mitsubishi.

  • P1ComfortNet / FITData
  • P2ComfortNet / FITData

FIT outdoor

Same P1/P2. Polarity matters.

  • P1DataData
  • P2DataData

Outdoor line — inverter drive

208/230 into the drive. No contactor slam. DC bus can stay live after the disconnect.

  • L1Line to the driveLine
  • L2Line to the driveLine
  • GNDEquipment groundLine

Landing

  • DataIndoor P1outdoor P1 · P2P2

    Data. Not 24 VAC Y.

  • LineL1 / L2outdoor

    208/230

Prove it

  • Daikin One / ComfortNet sees the outdoor.
  • P1/P2 landing and polarity. Never megger P1/P2.

Do not

  • Do not assume Mitsubishi S1/S2/S3 pinout.
  • Do not apply this to DX13SA / DC5SE / DX16TC.

P1/P2 is the published Daikin ComfortNet / FIT pair.

Sequence

  1. 1

    Call

    Indoor requests capacity on the data pair. Inverter ramps the compressor. No conventional contactor on the inverter SKU.

  2. 2

    Two-stage SKU

    If the plate is a two-stage communicating outdoor, you get low/high capacity and a TXV SC window — not a drive ramp. Leave the L5 playbook.

  3. 3

    Defrost / HP

    Reversing valve on HP SKUs. Outdoor coil sensor and defrost control are on this board, not the furnace IFC.

Faults on this IFC

Step 1, then 2, then 3. Expected reading and the fail branch sit under each check.

U4

Indoor/outdoor comm

lockout

Data pair between this outdoor and the communicating indoor is down.

  1. 1 Data pair, not 24 V

    On Daikin DZ20VC 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. Polarity, gauge, splices on the data pair. This is not 24 V Y.

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

  2. 2 Power both ends, then the outdoor status

    Indoor transformer and outdoor control both alive. Read the outdoor LED / 7-seg. Water in the outdoor control is the usual dead-end after a storm. Indoor must be communicating (DM96VC / AVPTC / AMVC / GMVC-class). GR9T96 / AR9T96 / 9-speed 24V cannot clear U4.

    Expect: Both controls powered. Outdoor showing a comm or address state, not a blank board.

  3. 3 Address / bias, then the control

    Communicating plates need a matching indoor address and sometimes a terminating bias. Swap is last: known-good pair + power both ends + correct address. One master. Leftover thermostat cable landed as ‘data’ will never train.

    Expect: Indoor sees the outdoor. No comm code after a power cycle.

L5 / E6

Compressor / drive

lockout

Inverter overcurrent (L5) or compressor start fail (E6). Inverter-SKU language.

  1. 1 Let it cool, then read the drive LED

    On Daikin DZ20VC overcurrent / overheat is often a dirty coil, a failed OD fan, or a locked compressor — not a dead inverter. Clear airflow, confirm the OD fan, and read the drive LED before you order a control. Confirm this cabinet is actually the inverter (DZ20VC), not a two-stage DX18TC.

    Expect: OD fan running. Coil clean. Drive LED decoded from THIS outdoor’s card.

  2. 2 Voltage and compressor windings

    Incoming voltage in range (this plate’s line-voltage code). Compressor windings even, no ground. A shorted compressor will kill a new drive. Winding/ground, inverter heat sink/cooling, supply voltage.

    Expect: Balanced windings. No winding to ground. Line voltage stable under load.

  3. 3 Charge and the drive last

    A starved or flooded compressor will overcurrent. Confirm SH/SC and charge weight. Only then condemn the inverter. Weigh-in vs nameplate + line-set. You do not ‘top off’ an inverter to clear L5.

    Expect: Charge on the nameplate. Drive code gone after a cool-down and a clean coil.

HPS

High pressure

lockout

Outdoor high-pressure protection. Airflow, overcharge, or restriction.

  1. 1 Heat rejection first

    On Daikin DZ20VC high pressure is outdoor airflow until proven otherwise. Fan running the right direction, coil clean, fins not folded, no recirc over a fence or through a garage. Outdoor fan actually running? Coil dirty?

    Expect: OD fan on, coil clean, discharge air leaving the top/side freely.

  2. 2 Head, subcooling, and liquid line

    Liquid pressure and liquid-line temperature → SC. High head + high SC = overcharge or non-condensables. High head + low SC = restriction or a dying compressor. Do not add gas because suction is low. Indoor airflow on the communicating CFM tables.

    Expect: SC vs the metering device on this plate (TXV ≠ piston).

  3. 3 Restriction vs the switch

    Drier, liquid-line kink, TXV inlet screen, or a non-feed indoor coil will stack head. Ohm / jumper-test the HPS only as a momentary prove, then restore it. A switch that opens on a known-good charge and clean coil is the switch. Weigh-in on inverter SKUs. SC window only if you have confirmed a two-stage TXV sibling.

    Expect: HPS closed at a normal liquid pressure for this refrigerant and OD ambient.

LPS

Low pressure

lockout

Low-pressure / freeze protection. Charge, indoor airflow, metering.

  1. 1 Airflow and freeze before you add gas

    On Daikin DZ20VC low pressure / freeze is indoor airflow or a starved coil until proven otherwise. Filter, blower, dirty A-coil, closed supplies. In heat mode, a iced outdoor coil is the same family. Do not add gas on a frozen indoor coil.

    Expect: Indoor air moving. Coil not iced. OD coil clear in heat.

  2. 2 SH / SC after a thaw

    Thaw fully. Then SH and SC vs the metering device. Low charge ices a piston. A TXV stuck closed ices with high SH. A restriction downstream of the ports fakes a low-charge chart. Indoor blower running the commanded CFM? Filter, coil.

    Expect: SH/SC in range for this refrigerant and device after a stable 10-minute run.

  3. 3 Leak, TXV, then the LPS

    Weigh-in if the chart says undercharge. Soap / electronic leak on joints and the coil. LPS that opens on a known-good charge and a clear coil is the switch — momentary test only, then restore. Weigh-in on inverter. TXV health check only after the SKU is known.

    Expect: Charge on the nameplate. LPS closed at a normal suction for this OD ambient.

Workflows

U4 with a GR9T96 indoor

Someone ran data wire to a 24V furnace.

  1. 1 Prove the call and the live code

    GR9T96 / AR9T96 cannot be the ComfortNet indoor. Land Y1/Y2/C only if this outdoor supports 24V fallback, or change the indoor to DM96VC / GMVC / AVPTC.

    Expect: Write whatever Outdoor inverter / communicating PCB is showing. Outdoor LED/display before you pull the disconnect. Daikin One / ComfortNet events name the outdoor fault in English when the bus is alive.

    If fail: No call at the IFC → stat / harness. Do not change gas parts.

  2. 2 Isolate the first failed step in the sequence

    U4 will never clear on data wire into a 9-speed 24V IFC. That is not a bad outdoor board.

    Expect: Two-stage SKU: If the plate is a two-stage communicating outdoor, you get low/high capacity and a TXV SC window — not a drive ramp. Leave the L5 playbook.

  3. 3 Confirm with a number, then the next part

    If the indoor is DM96VC and U4 is still up: polarity, splices, outdoor board power, then the outdoor PCB.

    Expect: Charge: Weigh-in on inverter SKUs (nameplate + line-set adders). SC on a confirmed two-stage TXV sibling only. · Data pair: Communicating indoor. GR9T96 data-wire landings will not train.

    If fail: Stay on this plate. The out-of-range reading is the part.

    If pass: Reading in range → the next step in this workflow is the repair.

Inverter vs two-stage SKU

Plate is dirty or the warehouse pulled ‘a Daikin 18–20.’

  1. 1 Prove the call and the live code

    DZ20VC = this inverter page. L5/E6 and weigh-in apply.

    Expect: Write whatever Outdoor inverter / communicating PCB is showing. Outdoor LED/display before you pull the disconnect. Daikin One / ComfortNet events name the outdoor fault in English when the bus is alive.

    If fail: No call at the IFC → stat / harness. Do not change gas parts.

  2. 2 Isolate the first failed step in the sequence

    DX18TC-class two-stage = different outdoor board. Charge by SC on a TXV coil. No L5 drive.

    Expect: Two-stage SKU: If the plate is a two-stage communicating outdoor, you get low/high capacity and a TXV SC window — not a drive ramp. Leave the L5 playbook.

  3. 3 Confirm with a number, then the next part

    DZ18VC: read that plate. Do not assume every ‘18’ is two-stage or every ‘20’ is inverter without the letter string. DX17VSS side-discharge is a different fan path — same comms idea, different cabinet.

    Expect: Charge: Weigh-in on inverter SKUs (nameplate + line-set adders). SC on a confirmed two-stage TXV sibling only. · Data pair: Communicating indoor. GR9T96 data-wire landings will not train.

    If fail: Stay on this plate. The out-of-range reading is the part.

    If pass: Reading in range → the next step in this workflow is the repair.

Test points

Charge

Weigh-in on inverter SKUs (nameplate + line-set adders). SC on a confirmed two-stage TXV sibling only.

Data pair

Communicating indoor. GR9T96 data-wire landings will not train.

Drive

L5/E6 only mean inverter overcurrent/start on this family. Confirm the SKU before you order a drive.

Gotchas

  • Indoor DM96VC E2 is a trap. Outdoor U4 is the bus. Do not swap those charts.
  • Goodman GSZC18 is a communicating HP cousin — different badge, same ‘data pair vs 24V indoor’ trap.

Related plates

Install this plate

Install DZ20VC as a communicating inverter heat pump. Weigh-in. U4/L5 live on this outdoor.

Inverter HP · ComfortNet / Daikin One · weigh-in · pair to DM96VC / AVPTC-class

Pair & charge

  • Communicating indoor required for full inverter behavior. 24V Y1/Y2 only if THIS outdoor supports fallback — read the diagram.
  • Weigh-in + adder. Not a GSZ14 contactor charge.
  • DZ18VC / DX18TC / DX17VSS are different outdoor controls. Do not steal their drive chart.

First fire

  1. 1Bus pair first. Cool then heat. U4 is comms — fix the pair before you weigh-in twice.

Do not on Daikin DZ20VC

  • Do not apply GSZ14 defrost-board steps as the primary diagnosis.
  • Do not treat furnace E-codes as this outdoor drive.

Maker literature

FieldBench does not host manufacturer files. Each link opens the maker’s own literature page in a new tab.

  • Daikin whole-house heat pumpsProduct pageDZ20VC is the inverter communicating HP plate. Current listing also shows DZ9VC as the refresh — match the outdoor sticker.Open manufacturer PDF
  • Daikin literature libraryLiterature searchComfortNet / Daikin One I/O and specs. Dealer login may be required for install PDFs.Open manufacturer PDF

Warranty and bulletins

Affected models, serial range, symptom, remedy, date. Maker files open on the manufacturer site.

All bulletins

  • Residential limited warranty

    warranty sheet

    Daikin furnace warranty

    Registered ComfortNet / Daikin One furnace warranty · Limited warranty certificate

    Open factsOpen manufacturer PDF

  • Dealer portals

    dealer

    Where remaining service letters live

    Current-year service letters not on a public literature page · Maker dealer portal

    Open factsOpen manufacturer PDF