Breville BES920 — Technical Repair Dossier

240V/50Hz | Australia/NZ Region

AI-Generated Technical Data — Verify Before Use

This dossier was compiled with AI assistance from exploded diagrams, supplier part listings, and community repair knowledge. Resistance values, part codes, and wiring references are indicative only. Always verify against your specific unit's service manual or a known-good measurement before ordering parts or performing electrical work. Specifications may vary between production runs and regional variants. Work on mains-connected appliances carries risk of electrocution and fire — if in doubt, engage a licensed appliance repairer.

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Machine Overview

Attribute	Detail
Model numbers	BES920BSS (brushed stainless), BES920BKS (black sesame)
Voltage / Frequency	240V / 50Hz (AU/NZ)
Power consumption	~1700W
Boiler architecture	Dual boiler — independent brew boiler (PID) + steam boiler
Portafilter	58mm commercial-style
Filter baskets	Dual wall (pressurised) and single wall (non-pressurised), multiple sizes
Water tank	2.0L removable, compatible with Breville Claris water filter
Pump	ULKA vibratory pump
Temperature control	Independent PID for brew boiler; pressure stat / thermostat for steam boiler
Display	Digital LCD with brew temperature adjustment
Integrated grinder	No — separate grinder required
Country of sale	Australia, New Zealand

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How This Machine Differs from the BES870 and BES800ES

This comparison is critical if you're diagnosing a BES920 using BES870/BES800ES muscle memory — the architectures are fundamentally different.

Feature	BES800ES / BES870	BES920
Thermal system	Single thermoblock	Dual boiler (brew + steam, independent)
Brew temperature control	Fixed or limited PID (thermoblock)	Full PID — user-adjustable brew boiler setpoint
Steam temperature control	Shared with brew path	Independent steam boiler with pressure stat
Heating elements	1 × thermoblock element	2 × elements (one per boiler) + cup warmer element
Temperature sensors	1–2 NTC thermistors	2 × NTC thermistors (one per boiler) + pressure stat
Solenoid valves	1 × 3-way brew solenoid	3-way brew solenoid + steam boiler solenoid
Flow meter	Not present (BES800ES) / present (BES870)	Present — critical for shot volume control
Pump	ULKA vibratory (shared part)	ULKA vibratory (shared part)
PCB complexity	Simpler	More complex — dual PID channels, more I/O
Integrated grinder	BES870: yes	No
Plumbing complexity	Simpler — fewer hose runs	More complex — two boiler feeds, check valves, more fittings
Failure complexity	Fewer failure points	More failure points; fault isolation requires identifying which boiler
Shot quality ceiling	Good	Higher — independent temperature control is the key advantage
Typical repair difficulty	Moderate	High — requires dual-boiler diagnosis methodology

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1. Component Test Table

Test with the machine unplugged unless otherwise noted. Use a digital multimeter.

Component	Location (Diagram Series)	Expected Resistance (cold / room temp)	Operating Voltage	Notes
ULKA EP5 main pump	Series 04 (04, 04.9)	~1.1–1.3 MΩ pin-to-pin; Diode mode: ~0.79V forward, OL reverse (field-verified, 240V AU)	240V AC	Internal diode blocks standard ohm readings — use diode test mode for definitive coil test. Hum without flow = blocked or seized. No hum = relay/PCB or wiring fault
ULKA NME boiler water pump	Series 05 area	~1.2 MΩ pin-to-pin; Diode mode: ~1.6V forward, OL reverse (field-verified, 240V AU)	240V AC	Higher diode-mode voltage than EP5 due to different coil impedance. Same diode testing applies
Group head heating element	Series 03 (group head)	~286–300 Ω (~197W) (field-verified across BES920 + BES900)	240V AC	Low wattage — maintains group head temp, not for boiling. Same part across BES900/920. Infinite = open element
Brew 3-way solenoid valve	Series 03 (03.x)	~2.2–2.6 kΩ (coil) (field-verified, 240V AU)	240V AC	Test coil resistance across terminals. Should read OL to ground on both pins. Mechanically stuck = no back-flush after shot
Brew boiler heating element	Series 03 (03.1–03.49)	~77.6 Ω (~742W) (field-verified)	240V AC	Infinite resistance = open circuit / failed element. Check element seal for leaks too
Steam boiler heating element	Series 05 (05, 05.4–05.25)	~47.7 Ω (~1208W) (field-verified)	240V AC	Lower resistance = higher wattage — steam boiler needs more power to reach/maintain steam pressure. Failure usually presents as no steam / weak steam
Brew NTC thermistor	Series 03 (brew boiler area)	~10 kΩ at 25°C; ~2–3 kΩ at 80°C	Signal voltage (3.3V or 5V DC)	Shorted NTC → PID sees overtemp, no heat. Open NTC → PID sees undertemp, may overheat
Steam NTC thermistor / pressure stat	Series 05 (05.4–05.25)	NTC: ~10 kΩ at 25°C; Pressure stat: continuity below setpoint	Signal / 240V AC	Pressure stat should show continuity when boiler is cold (unpressurised)
Thermostat	Near boiler	~0.1 Ω (continuity) (field-verified)	240V AC	Should pass continuity when cold. Open = failed thermostat
Thermal fuse — brew boiler	Series 03 (near element)	~0.4 Ω (continuity) (field-verified)	One-shot, 240V AC	Blown fuse (OL/infinite) = open circuit. Non-resettable. Indicates prior overtemp event — find root cause
Thermal fuse — steam boiler	Series 05 (near element)	~0.4 Ω (continuity)	One-shot, 240V AC	Same as above. Both boilers have independent fuses
Flow meter	Series 06 (06.6–06.67)	N/A (Hall effect sensor)	5V DC signal	Test with machine powered: 5V supply to sensor, pulsed output during water flow. No pulses = failed sensor or blocked impeller
PCB mains fuse	Series 02 (PCB assembly)	0 Ω (continuity)	240V AC protection	Usually a ceramic cartridge fuse. Blown fuse with no obvious cause → check for shorted element or pump
Cup warmer element	Series 01 (01.28)	1–5 kΩ (lower power element)	240V AC	Rarely fails; check if cup warmer completely non-functional

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2. Dual Boiler Logic — How It Works

Architecture Overview

The BES920 contains two completely independent thermal circuits sharing one pump and one water supply:

• Brew boiler (Series 03): A small-volume boiler dedicated solely to producing brew-temperature water (typically 90–96°C). It is PID-controlled — the PCB reads a NTC thermistor in the brew boiler and switches the brew heating element on/off to maintain the user-set temperature with high precision.

• Steam boiler (Series 05): A larger-volume boiler that operates at steam pressure (typically 120–130°C, ~1.5–2 bar). It is controlled by a pressure stat (or NTC + pressure sensor) rather than a direct PID loop. The steam boiler maintains pressure within a band; the heating element cycles on when pressure drops below the lower threshold.

Independent Operation

Both boilers can heat simultaneously. When you power on the machine, both boilers begin heating in parallel. The brew boiler reaches its setpoint first (it's smaller and runs at lower temperature). The steam boiler takes longer to reach steam pressure.

The digital display shows brew boiler temperature during warmup. A separate steam-ready indicator shows when the steam boiler has reached operating pressure.

Startup Sequence

1. Power on → PCB initialises, both boiler heating elements energise
2. Brew boiler heats rapidly to PID setpoint (typically 2–5 minutes depending on thermal mass)
3. Brew-ready indicator activates when brew boiler NTC reads within range of setpoint
4. Steam boiler continues heating toward pressure stat cutout point
5. Steam-ready indicator activates when steam pressure reaches operating threshold
6. Machine is now fully operational — brew circuit and steam circuit are thermally independent

Shot Delivery Sequence

1. User initiates shot → PCB activates pump (Series 04) and opens brew solenoid (Series 03)
2. Flow meter (Series 06) counts pulses as water passes through
3. Water from pump enters brew boiler, exits at brew temperature through group head
4. At target volume (pulse count), PCB deactivates pump and de-energises solenoid
5. 3-way solenoid redirects residual pressure to drip tray (back-flush)
6. Brew boiler PID continues regulating temperature between shots

Why This Matters for Diagnosis

Because the two boilers are independent, you can isolate faults:

• Shot cold but steam fine → brew boiler fault (element, NTC, or PID channel)
• No steam but shot temperature correct → steam boiler fault (element, pressure stat, or wiring)
• Both circuits dead → likely mains input, PCB fuse, or main PCB fault

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3. Circuit Topography

PCB Assembly (Series 02: 02, 02.4, 02.6, 02.8, 02.31, 02.32)

The main PCB handles: mains input switching, both boiler element relays, pump relay, solenoid drivers, flow meter signal input, both NTC thermistor ADC inputs, display output, and user button inputs.

⚠️ Testing Ulka Pumps — Diode Mode Required

Both the EP5 (main brew pump) and NME (boiler water pump) have an internal 1N4007 diode in series with the coil. A standard multimeter in resistance mode outputs only ~0.2–0.5V — insufficient to forward-bias the diode (~0.7V threshold). This means:

• Resistance mode: You'll see ~1–1.3 MΩ in one direction and OL in the other. This is normal — it's diode leakage, not coil resistance.
• Diode test mode: Pushes ~3V, enough to overcome the diode. This is the correct way to test pump coils.
  • Healthy EP5: ~0.79V forward, OL reverse
  • Healthy NME: ~1.6V forward, OL reverse (higher due to different coil impedance)
  • Dead coil: OL in both directions

Do not condemn a pump based on megaohm readings in resistance mode — always confirm with diode test.

Ulka Pump Condition Table (Diode Mode — 240V AU)

Use these field-verified readings to assess pump health. All readings taken with multimeter in diode test mode.

Pump	Condition	Diode Mode (Forward)	Resistance Mode	Verdict
EP5	Healthy (new)	~0.79V	~1.1–1.3 MΩ	✅ Good — replace if other symptoms point to pump
EP5	Degraded	~1.35V	~7.7 MΩ	⚠️ Winding breakdown — may buzz/run but won't deliver full pressure. Replace coil
EP5	Dead (open)	OL both directions	OL	❌ Open winding — no function
EP5	Dead (shorted diode)	~0V or very low both directions	Low Ω both directions	❌ Diode failed short — pump may buzz but won't pump
NME	Healthy	~1.6V	~1.2 MΩ	✅ Good — higher diode-mode voltage is normal (higher-impedance coil, lower wattage)
NME	Dead (open)	OL both directions	OL	❌ Open winding — no function

How to read the table: A healthy EP5 shows ~0.7V diode drop + minimal coil voltage. The NME reads higher (~1.6V) because its smaller, lower-wattage coil has higher resistance — more voltage drops across the winding during diode test. If an EP5 reads significantly above ~0.8V (e.g. 1.35V), the extra voltage is from degraded winding resistance — the pump is failing even if it still runs.

All pumps should read OL in reverse — any reverse reading indicates a failed diode.

Test Points by Symptom

No power (display dead, no heating)

• Check mains cord and plug (Series 09, 09.17/09.18)
• Check PCB mains fuse (Series 02) — locate ceramic fuse on PCB input stage
• Measure mains voltage at PCB input terminals (240V AC expected) — requires caution, machine plugged in
• If fuse blown repeatedly: suspect shorted element (test both heating elements for isolation to chassis)

Brew boiler not heating (display shows brew temp stuck at ambient)

• Confirm display shows brew NTC reading (not frozen/error code)
• Test brew NTC thermistor: disconnect from PCB, measure resistance, compare to temperature curve (~10 kΩ at 25°C)
• Test brew heating element for continuity (unplug machine)
• Test brew thermal fuse continuity (in series with element circuit)
• Check relay output on PCB: with machine powered and brew boiler below setpoint, relay should energise (audible click, 240V AC across element terminals)

Steam boiler not heating (no steam, steam pressure gauge low)

• Test steam heating element resistance and thermal fuse (same method as brew boiler)
• Test pressure stat / steam NTC: should show continuity / expected resistance when cold
• Check steam boiler relay on PCB: should energise when steam pressure below setpoint

Pump not activating (no water flow on shot)

• Confirm pump receives 240V AC during shot initiation (requires powered test — caution)
• Test pump coil resistance (~1.1–1.3 MΩ pin-to-pin expected)
• Check pump relay on PCB
• Inspect flow meter signal wire — PCB may suppress pump if flow meter shows fault condition

Display / PID fault (error codes, frozen display, erratic temperature)

• Check display module connector (Series 02 display cable, 02.31/02.32)
• Inspect NTC wiring for damage or disconnection
• A shorted NTC will cause the PID to see max temperature and refuse to heat — check NTC resistance
• An open-circuit NTC will cause temperature runaway on some firmware versions

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4. Common Failure Points

Ranked by observed frequency in AU repair community:

Rank	Failure	Boiler Affected	Symptoms	Diagnosis
1	Brew boiler scale buildup	Brew	Shot temperature unstable, slow to reach setpoint, reduced flow	Descale cycle; inspect element for scale jacket
2	3-way brew solenoid valve failure	Brew	No back-flush after shot, coffee grounds in drip tray, pressure retained in portafilter	Test solenoid coil resistance; inspect valve seat for debris
3	Brew NTC thermistor failure	Brew	PID shows error / ambient temp / runaway	Test thermistor resistance vs temperature curve
4	Brew heating element failure	Brew	Shot cold, brew boiler won't reach setpoint, element OL on meter	Test resistance; check thermal fuse in series
5	Steam heating element failure	Steam	No steam or very weak steam, steam boiler cold	Test resistance; check thermal fuse in series
6	Flow meter failure	Both (pump control)	Pump runs indefinitely, shot volume inconsistent, machine won't stop shot	Check Hall effect sensor supply voltage and pulse output
7	Steam boiler pressure stat failure	Steam	Steam boiler overheats / cycles incorrectly / safety valve venting	Test pressure stat continuity at ambient (should be closed)
8	PCB / relay failure	Either or both	One or both boilers not heating despite good elements, pump not activating	Board-level diagnosis; check relays for burn marks or failed contacts

Note on dual-element failure sequencing: The brew boiler element is under more thermal stress (rapid heat-cool cycles per shot) while the steam boiler element runs more continuously but at lower relative load. Brew boiler element or its NTC tends to fail first in heavily used machines.

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5. Diagnostic Trees

Tree A: Brew Boiler Not Reaching Temperature (Shot Too Cold)

Shot is cold / PID setpoint not reached
│
├─ Is the display showing a temperature reading?
│   ├─ NO / Error code → NTC thermistor fault (open or shorted)
│   │   └─ Test brew NTC resistance → replace if out of spec
│   │
│   └─ YES (temp stuck at ambient or climbing slowly)
│       │
│       ├─ Does temp rise at all during warm-up?
│       │   ├─ NO → Element or thermal fuse open
│       │   │   ├─ Test brew heating element resistance (expect 30–80 Ω)
│       │   │   ├─ OL result → replace element
│       │   │   └─ Good element → test thermal fuse continuity → replace if blown
│       │   │       (also find root cause of overtemp event)
│       │   │
│       │   └─ YES (rises but slowly / never reaches setpoint)
│       │       ├─ Heavy scale on element → descale, inspect element
│       │       ├─ NTC reading low (element heating but PID under-reading) → test NTC
│       │       └─ Partial element failure → test resistance (should be ~uniform)
│       │
│       └─ Temp reaches setpoint but shot still cold?
│           └─ Group head heat loss → check pre-infusion / idle time
│               or shower screen/dispersion block scale

Tree B: Steam Pressure Weak / Steam Boiler Fault

Weak or no steam
│
├─ Does steam boiler heat at all? (feel housing after 10 min)
│   ├─ Cold → No power to steam boiler
│   │   ├─ Test steam element resistance
│   │   │   ├─ OL → failed element → replace
│   │   │   └─ Good → test thermal fuse in series → replace if blown
│   │   └─ Both good → check PCB steam relay / wiring
│   │
│   └─ Warm but low pressure
│       ├─ Scale on steam boiler element → reduced heat transfer → descale
│       ├─ Pressure stat set too low or failed → test continuity cold
│       │   └─ Stat stays open when cold → failed → replace
│       ├─ Steam boiler safety valve weeping → steam escaping before full pressure
│       └─ Steam wand blocked → clear wand tip and steam valve (Series 09)
│
└─ Steam fine but hot water output weak?
    └─ Hot water solenoid / valve issue (Series 09.21 hot water wand comp)

Tree C: Machine Trips RCD on Power-On

RCD trips immediately or within seconds of power-on
│
├─ Trips instantly on power-on
│   ├─ Disconnect steam boiler element → re-test
│   │   ├─ RCD holds → steam element shorted to chassis → replace element + check element seal
│   │   └─ Still trips → disconnect brew boiler element → re-test
│   │       ├─ RCD holds → brew element shorted → replace + check seal
│   │       └─ Still trips → pump or PCB shorting → isolate and test
│   │
│   └─ Note: test each element for chassis continuity with multimeter
│       (any reading from element terminal to chassis ground = fault)
│
├─ Trips after ~30–60 seconds (warm trip)
│   ├─ Element seal failure — water tracking to chassis
│   │   └─ Inspect both element seals / O-rings for cracks or weeping
│   └─ Thermal fuse holder tracking when hot → inspect insulation
│
└─ Trips only during steam use
    └─ Steam element insulation breakdown at temperature → replace steam element

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6. Exploded Diagrams & Resources

Diagram 1 — External Housing, Panels, User-Facing Components

Key series:

• 08 — Rear panel, back housing, ventilation grille, electrical covers
• 09 — Steam wand, hot water wand comp (09.21), steam valve, seals, fittings, power cord entry (09.17 / 09.18)
• 10 — Top panel, cup-warming tray, side panels, brackets
• 11 — Control electronics / display panel, PCB enclosures (incl. wires)
• 12 — Internal frame / chassis
• 13 — Drip tray assembly (13, 13.1, 13.4)
• 14 — Group head area, brew platform, portafilter rest (14.1–14.17)
• 15 — Portafilter, filter baskets (single/dual wall), tamper, accessories (15.1–15.10)

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Diagram 2 — Internal Mechanisms, Boilers, Pump, Hydraulics, Electronics

Key series:

• 01 — Cup-warming tray heating element (01.28 incl. wires), brackets
• 02 — Main control PCB assembly (02, 02.4, 02.6, 02.8, 02.31, 02.32 with wires), display module, buttons
• 03 — Brew boiler, heating element, group head, shower screen, gaskets, 3-way solenoid valve, dispersion block, seals (03.1–03.49)
• 04 — Pump assembly and mounting hardware (04, 04.9)
• 05 — Steam boiler, heating element, pressure stat/sensor, safety valve, fittings (05, 05.4–05.25)
• 06 — Base frame, hydraulic plumbing, flow meter, check valves, hose connections (06.6–06.67)
• 07 — Water tank, housing/cradle (07A incl. mesh from PDC1707), lid, tank connection valve/seal (07, 07A, 07.13–07.31)

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Diagram 3 — Claris Filter Assembly

• 07.1 — Claris filter cartridge
• 07.2 — Filter holder / adapter

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Source: Appliance Supplies AU — BES920BKS parts listing

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Confirmed Part Codes

BES920-specific parts:

Code	Notes
BES9200128	BES920-specific component
BES9200232	BES920-specific component
BES920031	BES920-specific component
BES9200345	BES920-specific component

Shared / variant codes (BES900-series, may apply to BES920):

Code	Code	Code	Code
BES9000123	BES9000231	BES900028	BES9000311
BES9000321	BES9000326	BES9000338	BES9000342
BES9000349	BES9000513	BES900056	BES900059
BES9000619	BES9000620	BES9000626	BES900066
BES9000723	BES9000927	BES9000928	BES9000937
BES9001015	BES9001510	BES900155	BES900156
BES900157	BES900159

SP-series confirmed codes:

Code	Notes
SP0001634	Confirmed for BES920
SP0001695	Confirmed for BES920

Always confirm part applicability to your specific model variant (BES920BSS vs BES920BKS) and production date before ordering. Part numbers may differ between AU and international variants.

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7. Manual & Resource Search Strings

Use these exact strings in search engines, iFixit, and YouTube:

Breville BES920 service manual
Breville BES920 repair guide
BES920BSS disassembly
BES920 dual boiler element replacement
BES920 flow meter replacement
BES920 brew boiler scale descale
BES920 NTC thermistor replacement
BES920 3-way solenoid valve repair
BES920 PID temperature calibration
BES920 no steam fault
BES920 RCD trip fault
"BES920" site:home-barista.com
"BES920" site:coffeegeek.com
"BES920" filetype:pdf service
Breville dual boiler espresso repair AU
BES900 series repair

Parts suppliers (AU/NZ):

• Appliance Supplies AU
• Breville Spare Parts AU
• Espresso Parts AU
• eBay AU — search BES920 parts or specific part codes

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8. Known Quirks & Gotchas

PDC1707 Water Tank Housing Change (07A)

A running production change introduced a revised water tank cradle/housing (part reference 07A, incorporating mesh from PDC1707). Units with this change use different tank seals from earlier production. If ordering tank seals or the tank connection valve/seal assembly, check your machine's production date code. Using the wrong seal can result in slow tank leaks that are easy to miss until water tracks to electrical components.

Scale Builds Faster in the Brew Boiler

The brew boiler is significantly smaller volume than the steam boiler. With the same water hardness, it will scale up proportionally faster. Descale cycles treat both boilers, but in hard water areas the brew boiler should be the primary concern. Signs: brew temperature instability, PID cycling more frequently, reduced flow rate. Do not skip descaling — heavy scale can thermally insulate the element and cause thermal fuse failure.

PID Calibration Drift

The brew boiler PID setpoint can drift over time, particularly after PCB or NTC replacement. If shots taste different at the same grind/dose and the display shows the usual setpoint, the NTC may be reading slightly high or low. Cross-check actual brew boiler temperature (if possible) against the displayed value. Some users offset the setpoint by 1–2°C after NTC replacement to account for sensor variance.

Dual Element Failure Sequencing

The brew boiler element is subject to more thermal cycling stress (heats and cools with each shot cycle) while the steam boiler element runs more continuously but at a more stable temperature. In practice, the brew boiler element or its NTC tends to fail first in high-use machines. If you're preemptively servicing a heavily used BES920, prioritise checking the brew boiler circuit first.

Check Which Boiler Is Faulty Before Disassembly

Before pulling the machine apart, use the symptom table:

• Cold shots + normal steam → brew circuit fault → focus on Series 03 / brew boiler
• Normal shots + no steam → steam circuit fault → focus on Series 05
• Both circuits dead → PCB/power fault → focus on Series 02

Identifying the faulty boiler first saves significant disassembly time — the two boiler assemblies are in different areas of the chassis and require different access paths.

Steam Boiler Safety Valve Weeping

If you hear intermittent hissing from the rear of the machine during steam operation, the steam boiler safety valve (Series 05) may be weeping. This is sometimes caused by scale debris partially holding the valve open rather than true valve failure. A descale cycle may resolve it; if not, the safety valve is a replaceable item.

Flow Meter — Debris Sensitivity

The flow meter impeller (Series 06) is sensitive to debris. If a silicone hose fragment, scale chip, or assembly residue enters the flow path, the impeller can jam or spin erratically, causing the PCB to miscount shot volume. Symptom: shot volume becomes inconsistent or the pump runs too long / stops too early. Disassemble and inspect the flow meter impeller chamber before condemning the sensor electronics.

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9. Cross-References

Shared Components with BES870

These parts are believed to be shared between the BES920 and BES870 (verify before ordering — Breville sometimes uses visually identical but dimensionally different parts across model lines):

Component	Series	Notes
ULKA pump body	Series 04	Same pump family; verify mounting bracket and hose fitting dimensions
3-way brew solenoid valve	Series 03	Same solenoid coil resistance range; valve body may differ
Group head gasket	Series 03	58mm portafilter gasket — same spec, likely shared
Shower screen	Series 03	58mm, likely shared across BES900-series
Portafilter and baskets	Series 15	58mm system — accessories are shared across the range
Drip tray assembly	Series 13	Check dimensions — may differ between models

Components That Do NOT Transfer Between BES870 and BES920

Component	Reason
Brew boiler assembly	BES920 has a dedicated brew boiler vessel; BES870 uses a thermoblock — fundamentally different architecture
Steam boiler assembly	BES920-only component; BES870 does not have a separate steam boiler
Main PCB	Completely different — BES920 PCB handles dual boiler control, dual NTC inputs, more relay outputs
Flow meter	BES870 variant differences; plumbing location and connector may differ
Steam boiler heating element	BES920-specific boiler dimensions
NTC thermistors	May share the same sensor spec but are located in different assemblies with different harness connectors
Water tank housing (07A)	BES920 PDC1707 variant uses a specific tank cradle; do not assume BES870 tank fits
Power cord / inlet assembly	Different wattage / fusing between models; do not swap

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Dossier compiled from AU supplier exploded diagrams, confirmed part codes, and community repair knowledge. Always verify against service documentation for your specific unit.