Side by side

3-pin vs 4-pin PC fan connectors

The fourth contact is normally PWM control on the documented fan type, but header modes differ. Verify the exact fan, board rating and fan-control mode; do not infer automatic speed regulation.

Computer-generated illustration, not a photograph. — P343 · Connector3-pin PC fan connector / motherboard header

How they differ

3-pin PC fan connector / motherboard header Look for the fan header label on the board and three positions in the fan connector; compare the keyed guide and check the exact fan/board manuals.
4-pin PWM PC fan connector / motherboard header Check the board marking (CPU_FAN, SYS_FAN or similar) and fan plug guide, then verify the pin functions in the exact motherboard manual.

At a glance

Source-scoped form facts; counts, variants and unknowns are distinct
Field	3-pin PC fan connector / motherboard header	4-pin PWM PC fan connector / motherboard header
Type	Connector	Connector
Family	PC internal	PC internal
Shape	row header	row header
Nominal contacts	Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.	Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.
Positions / cavity span	3 (Noctua NF-A8 FLX fan assembly)S835Source-scoped examples are separate; select the exact variant and measured axis. Noctua NF-A8 FLX fan assembly. Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.	4 (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.
Contact rows	1 (ASRock H81M CHA_FAN2/PWR_FAN1)S834Current primary-source scoped values; named examples remain separate and unknowns are not inferred from illustrations. Exact equipment variant ASRock H81M CHA_FAN2/PWR_FAN1, manual contact arrangement only; no generic component family geometry. Quantity context: Source manual contact row.	1 (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.
Connector role	3-pin fan cable connector (Noctua NF-A8 FLX fan assembly)S835Source-scoped examples are separate; select the exact variant and measured axis. Noctua NF-A8 FLX fan assembly. Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.	Vertical male PCB header (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.
Key distinction	Three contacts do not establish automatic speed control: the motherboard must support the correct fan-control method.	Four contacts identify a candidate PWM form; they do not prove a particular board header offers PWM mode or adequate power.

Full evidence ledger and sources ↓

Illustrations are computer-generated with prior AI visual review; independent technical and rights review pending. A comparison is not a compatibility verdict.

This comparison stays within one evidence layer.

All selected records are Connector records. Similar layer does not mean compatible, interchangeable or safe to mate.

Families represented: PC internal

Matching diagram / concept only

Fit and speed control differ.

The motherboard manual decides the available control mode.

The motherboard manual decides the available control mode. Concept diagram, not physical geometry or a connection approval.

Three-pin PC fan →Four-pin PWM PC fan →

Not a hardware compatibility verdict. S454 · S455

The reference ledger

Read the same question across.

2 selected records · 15 fields
No score. No compatibility verdict.

On a narrow screen, scroll the table sideways or open the field-by-field reading view below. Illustrations are not a size comparison.

Comparison of selected field notes; source links accompany each documented specification
What you are comparing	P343 / Connector3-pin PC fan connector / motherboard header Identification schematic · not to scale · drawing review pending	P344 / Connector4-pin PWM PC fan connector / motherboard header Identification schematic · not to scale · drawing review pending
Layer	Connector	Connector
Key distinction	Three contacts do not establish automatic speed control: the motherboard must support the correct fan-control method.	Four contacts identify a candidate PWM form; they do not prove a particular board header offers PWM mode or adequate power.
Nominal contacts	Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.	Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.
Positions / cavity span	3 (Noctua NF-A8 FLX fan assembly)S835Source-scoped examples are separate; select the exact variant and measured axis. Noctua NF-A8 FLX fan assembly. Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.	4 (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.
Populated contacts	Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.	4 (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.
Contact rows	1 (ASRock H81M CHA_FAN2/PWR_FAN1)S834Current primary-source scoped values; named examples remain separate and unknowns are not inferred from illustrations. Exact equipment variant ASRock H81M CHA_FAN2/PWR_FAN1, manual contact arrangement only; no generic component family geometry. Quantity context: Source manual contact row.	1 (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.
Contact pitch	Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.	2.54 mm Contact mating centerline pitch (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.
Dimensions / axis	Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.	3.5 mm PC tail length (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.
Connector role	3-pin fan cable connector (Noctua NF-A8 FLX fan assembly)S835Source-scoped examples are separate; select the exact variant and measured axis. Noctua NF-A8 FLX fan assembly. Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.	Vertical male PCB header (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.
Coupling / latch	Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.	Lock to mating part: yes (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.
Keying / polarization	Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.	Polarized to mating part: yes; keyed to mating part: no (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.
Common PC form	Three contact positions; voltage and control must be checked on exact equipmentC343A	Not an equivalent field
Role and recognition scope	Fan cable end / counterpart header — Noctua 3-pin fan family (bounded FAQ scope). Original qualitative study only; no wiring or fit approval.C343C · C343D · C343E	Board header — MSI B550-A PRO CPU_FAN1 / PUMP_FAN1 / SYS_FAN1–6. Original qualitative study only; no wiring or fit approval.C344C · C344D · C344E
Documented extra function	Not an equivalent field	Fourth contact conveys PWM control on specified PWM fan variantsC344A
Evidence	C343A,C343B,C343C,C343D,C343E,C343W → Independent review pending	C344A,C344B,C344C,C344D,C344E → Independent review pending

Read field by field — no sideways scrolling

The same selected records, fields, values and source links as the table. Missing fields remain non-equivalent; no values are merged.

Layer

3-pin PC fan connector / motherboard headerP343 / Connector: Connector
4-pin PWM PC fan connector / motherboard headerP344 / Connector: Connector

Key distinction

3-pin PC fan connector / motherboard headerP343 / Connector: Three contacts do not establish automatic speed control: the motherboard must support the correct fan-control method.
4-pin PWM PC fan connector / motherboard headerP344 / Connector: Four contacts identify a candidate PWM form; they do not prove a particular board header offers PWM mode or adequate power.

Nominal contacts

3-pin PC fan connector / motherboard headerP343 / Connector: Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.
4-pin PWM PC fan connector / motherboard headerP344 / Connector: Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.

Positions / cavity span

3-pin PC fan connector / motherboard headerP343 / Connector: 3 (Noctua NF-A8 FLX fan assembly)S835Source-scoped examples are separate; select the exact variant and measured axis. Noctua NF-A8 FLX fan assembly. Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.
4-pin PWM PC fan connector / motherboard headerP344 / Connector: 4 (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.

Populated contacts

3-pin PC fan connector / motherboard headerP343 / Connector: Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.
4-pin PWM PC fan connector / motherboard headerP344 / Connector: 4 (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.

Contact rows

3-pin PC fan connector / motherboard headerP343 / Connector: 1 (ASRock H81M CHA_FAN2/PWR_FAN1)S834Current primary-source scoped values; named examples remain separate and unknowns are not inferred from illustrations. Exact equipment variant ASRock H81M CHA_FAN2/PWR_FAN1, manual contact arrangement only; no generic component family geometry. Quantity context: Source manual contact row.
4-pin PWM PC fan connector / motherboard headerP344 / Connector: 1 (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.

Contact pitch

3-pin PC fan connector / motherboard headerP343 / Connector: Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.
4-pin PWM PC fan connector / motherboard headerP344 / Connector: 2.54 mm Contact mating centerline pitch (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.

Dimensions / axis

3-pin PC fan connector / motherboard headerP343 / Connector: Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.
4-pin PWM PC fan connector / motherboard headerP344 / Connector: 3.5 mm PC tail length (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.

Connector role

3-pin PC fan connector / motherboard headerP343 / Connector: 3-pin fan cable connector (Noctua NF-A8 FLX fan assembly)S835Source-scoped examples are separate; select the exact variant and measured axis. Noctua NF-A8 FLX fan assembly. Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.
4-pin PWM PC fan connector / motherboard headerP344 / Connector: Vertical male PCB header (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.

Coupling / latch

3-pin PC fan connector / motherboard headerP343 / Connector: Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.
4-pin PWM PC fan connector / motherboard headerP344 / Connector: Lock to mating part: yes (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.

Keying / polarization

3-pin PC fan connector / motherboard headerP343 / Connector: Not recordedNot recorded in a normalized source-scoped field. Consult the exact part/revision; no value inferred from illustrations.
4-pin PWM PC fan connector / motherboard headerP344 / Connector: Polarized to mating part: yes; keyed to mating part: no (Molex 470531000 (47053-1000))S854Source-scoped examples are separate; select the exact variant and measured axis. Molex 470531000 (47053-1000). Named primary-source example only. Identification facts do not certify mating, electrical compatibility, fabrication or powered use.

Common PC form

3-pin PC fan connector / motherboard headerP343 / Connector: Three contact positions; voltage and control must be checked on exact equipmentC343A
4-pin PWM PC fan connector / motherboard headerP344 / Connector: Not an equivalent field

Role and recognition scope

3-pin PC fan connector / motherboard headerP343 / Connector: Fan cable end / counterpart header — Noctua 3-pin fan family (bounded FAQ scope). Original qualitative study only; no wiring or fit approval.C343C · C343D · C343E
4-pin PWM PC fan connector / motherboard headerP344 / Connector: Board header — MSI B550-A PRO CPU_FAN1 / PUMP_FAN1 / SYS_FAN1–6. Original qualitative study only; no wiring or fit approval.C344C · C344D · C344E

Documented extra function

3-pin PC fan connector / motherboard headerP343 / Connector: Not an equivalent field
4-pin PWM PC fan connector / motherboard headerP344 / Connector: Fourth contact conveys PWM control on specified PWM fan variantsC344A

Evidence

3-pin PC fan connector / motherboard headerP343 / Connector: C343A,C343B,C343C,C343D,C343E,C343W →
Independent review pending
4-pin PWM PC fan connector / motherboard headerP344 / Connector: C344A,C344B,C344C,C344D,C344E →
Independent review pending

Your next step

Use the distinction in context.

Open the field notes Read source-linked facts and limitations.Compare another pair Start from a common confusion.Check a connection A comparison is not a compatibility verdict.

Continue the distinction

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Browse every comparison →

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Add a field note

Evidence behind this page

Scope first. Source second. Approval separate.

6 linked sources · 11 scoped claims · 0 sources with inspection/access flags.

Page scope: Evidence behind the compared records; the editorial comparison still needs separate review.

Assessment 2026-10-22 · earliest scheduled source review 2027-01-07. This is a recorded-date assessment, not a live source check. Page-level independent review is not established by this panel.

Inspect 6 source scopes, access limits and dates

S454 · Noctua 3-pin and 4-pin motherboard fan FAQ

Noctua · Unclassified publisher domain · inspected 2026-10-09 · due 2027-01-07

Within inspection window

Scoped support: Fan-family contact-count and conditional motherboard control; Noctua examples only.

Not established / limitations: Fan color, connector shape and header modes vary; not a universal polarity or current-rating certificate.

Locator: 3-pin fan on 4-pin PWM header; 4-pin fan on 3-pin header; PWM versus DC control

S455 · Noctua microcontroller fan control guide

Noctua · Unclassified publisher domain · inspected 2026-10-09 · due 2027-01-07

Within inspection window

Scoped support: Separate power, speed-sense and PWM functions in named Noctua 4-pin fans.

Not established / limitations: No color scheme, wiring voltage, or connector variant is inferred for other makers.

Locator: Introduction / What are the wires of my 4-pin fan used for?

S591 · MSI B550-A PRO User Guide, version 6.0 (2024/02)

MSI · Unclassified publisher domain · inspected 2026-10-13 · due 2027-01-11

Within inspection window

Scoped support: Named B550-A PRO board header identities, diagram-level contact/key arrangements, control modes and RGB mismatch warnings.

Not established / limitations: Observed document is not a real-hardware inspection, installed-device approval, wiring guide, current revision guarantee or manufacturing specification.

Locator: PDF pp.33, 36–38, 40–41; p.59 / printed ix revision history. Source diagrams visually inspected at zero-based pages 32,35,36,37,39,40,58.

S592 · Noctua PWM specifications white paper — connector roles and voltage scope

Noctua · Unclassified publisher domain · inspected 2026-10-13 · due 2027-01-11

Within inspection window

Scoped support: Manufacturer-wide bounded 4-pin PWM fan family; female cable versus male board role and 5/12/24V model distinction.

Not established / limitations: Observed document is not a real-hardware inspection, installed-device approval, wiring guide, current revision guarantee or manufacturing specification.

Locator: PDF pp.1–3: scope, cable/PCB roles and connector images. PDF pages 2–3 visually inspected. No publication revision/date identified; not asserted current-revision equivalent.

S593 · Noctua FAQ — fan pin-configuration and voltage families

Noctua · Unclassified publisher domain · inspected 2026-10-13 · due 2027-01-11

Within inspection window

Scoped support: Noctua fan family voltage range; no wire-colour table or source image promoted.

Not established / limitations: Observed document is not a real-hardware inspection, installed-device approval, wiring guide, current revision guarantee or manufacturing specification.

Locator: Main FAQ prose reviewed 2026-10-13. Inline fan drawings could not be visually acquired in this run; text-only observation, no image qualification.

S834 · H81M User Manual

ASRock · Unclassified publisher domain · inspected 2026-10-21 · due 2027-01-19

Within inspection window

Scoped support: Exact named pinout variant only; not capability or compatibility approval.

Not established / limitations: Source scope and unresolved evidence are preserved in the engineering variant.

Locator: Section 'Onboard Headers and Connectors', Chassis and Power Fan Connectors (3-pin CHA_FAN2, 3-pin PWR_FAN1) printed p. 25, and CPU Fan Connectors (3-pin CPU_FAN2) printed p. 26

Trace 11 claims to their source records

C343A · P343

Noctua explains that its 3-pin fan connector can be used on many 4-pin motherboard fan headers with the fourth PWM position unused.

Claim scope: Manufacturer-specific family/physical identification only. No inferred device wiring, mating verification or installation approval.

Source links: S454 · Evidence trail → (private workspace)

C343B · P343

Speed regulation for a three-pin fan depends on a motherboard supporting DC or voltage control; a four-pin header alone is not a speed-control guarantee.

Claim scope: Manufacturer-specific family/physical identification only. No inferred device wiring, mating verification or installation approval.

Source links: S454 · Evidence trail → (private workspace)

C343C · P343

For Noctua’s described 3-pin fan connection to a 4-pin header, the separate PWM position remains unused.

Claim scope: V142: named MSI B550-A PRO manual version 6.0 (2024/02) or explicitly identified Noctua family only. Role/recognition evidence, not generic wiring, safe mating, pinout approval, dimensions or installed-device certification.

Source links: S454 · Evidence trail → (private workspace)

C343D · P343

Noctua says automatic control can depend on motherboard voltage regulation; pulsing power is not equivalent to lowering the supply voltage.

Source links: S454 · Evidence trail → (private workspace)

C343E · P343

Noctua documents fans across 5V, 12V and 24V families; a contact-count label is not a voltage identification.

Source links: S593 · Evidence trail → (private workspace)

C343W · P343

The named ASRock H81M CHA_FAN2 and PWR_FAN1 diagrams show three positions in one inline row. The manual gives no pitch or exact header component part.

Claim scope: Exact equipment variant ASRock H81M CHA_FAN2/PWR_FAN1, manual contact arrangement only; no generic component family geometry.

Source links: S834 · Evidence trail → (private workspace)

C344A · P344

Noctua distinguishes its four-pin PWM fan connection by a fourth control signal; three-pin motherboard connection may not provide PWM control.

Claim scope: Manufacturer-specific family/physical identification only. No inferred device wiring, mating verification or installation approval.

Source links: S454 · S455 · Evidence trail → (private workspace)

C344B · P344

Motherboard documentation—not the number of header pins—determines whether its fourth position is implemented as PWM.

Claim scope: Manufacturer-specific family/physical identification only. No inferred device wiring, mating verification or installation approval.

Source links: S454 · S455 · Evidence trail → (private workspace)

C344C · P344

Noctua distinguishes the female fan-cable connector from male PCB headers and male cable connectors.

Source links: S592 · Evidence trail → (private workspace)

C344D · P344

Noctua’s PWM white paper covers 5V, 12V and 24V four-pin models unless otherwise stated.

Source links: S592 · Evidence trail → (private workspace)

C344E · P344

B550-A PRO lists Auto for CPU_FAN1, PWM for PUMP_FAN1 and DC for SYS_FAN1–6 as default modes.

Source links: S591 · Evidence trail → (private workspace)

Prepare this page for review →Read the evidence method →

Recorded evidence only. An inspection date, publisher label, source link or generated packet is not independent technical review, hardware testing, fabrication approval or a compatibility verdict.