Power Supplies
Serviceable power-supply harnesses and board transitions with Mini-Fit Jr. power-supply heritage.
Molex 4.2mm Fit power connectors
Molex Mini-Fit Jr. connectors for classic power interconnects
Select 5557 and 5559 housings, 5556 and 5558 terminals, HCS terminal options, headers, TPA2 variants, wire range, and circuit count for Mini-Fit Jr. harness builds.
4.20mm Pitch2-24 Circuits16-28 AWG600V
Why Molex Mini-Fit Jr. connectors exist
Molex Mini-Fit Jr. is the 4.2mm pitch Fit family for classic dual-row power interconnects. It is common in power supplies, appliances, telecom equipment, non-sealed automotive electronics, and production test fixtures that need a serviceable power disconnect.
The standard wire-to-wire stack uses a 5557 receptacle housing with 5556 female terminals and a 5559 plug housing with 5558 male terminals. Board connections use matching vertical or right-angle headers such as 5566, 5569, and 46999 series headers.
Mini-Fit Jr., Mini-Fit Plus, TPA2, and BMI variants intermate when the exact housing and terminal combination is selected correctly. Current is set by the terminal, wire, circuit count, and temperature, not by the housing name alone.
MiniProto stocks 39-01 housings across 2-24 circuits, 39-03 black housings, and 46999 headers in the live configurator catalog.
Why teams choose Molex Mini-Fit Jr.
Mini-Fit Jr. is the familiar Fit choice when a harness needs broad availability, dual-row density, board-header options, and more power headroom than smaller Fit families can provide.
Widely Available
The 5557, 5559, 5556, 5558, and header families are common enough to quote quickly across prototype and production quantities.
Power Dense
Dual-row 4.2mm housings cover 2-24 circuits without moving to a much larger high-current family.
Variant Friendly
TPA2, Plus, BMI, black, natural, panel-ear, vertical-header, and right-angle-header options cover many mechanical layouts.
Where Molex Mini-Fit Jr. earns its place
Appliances
Dishwasher, dryer, refrigerator, and other appliance harness breakpoints where 4.2mm pitch power connectors fit.
Telecom Equipment
Backplanes, fan trays, servers, and cabinet wiring where dual-row power circuits need repeatable service access.
Fit family comparison
Pick the Fit family by pitch, wire range, circuit count, and the exact terminal and wire condition behind the current rating.
Nano-Fit
Compact signal and power, tight packaging
2.5mm
20-26 AWG
- Max Current*
- 8.0A with 105300 terminals and 20 AWG in a 2-circuit wire-to-board set
- Circuits
- 2-8 single / 4-16 dual
Micro-Fit 3.0
Mid-density power and signal workhorse
3.0mm
18-30 AWG
- Max Current*
- 8.5A with 43030 terminal and 18 AWG
- Circuits
- 2-12 single / 2-24 dual
Ultra-Fit
Compact 600V power with glow-wire options
3.5mm
16-22 AWG
- Max Current*
- 14A with 172253 tin terminals and 16 AWG in a 2-circuit single-row wire-to-board set
- Circuits
- 2-8 single / 4-16 dual
Mini-Fit Jr.
Classic power interconnect
4.2mm
16-28 AWG
- Max Current*
- 9A with 5556 terminal and 24-18 AWG variant; 13A with 45750 HCS terminal and 16 AWG
- Circuits
- 2-24 dual
Mega-Fit
High-current power runs
5.7mm
10-16 AWG
- Max Current*
- 23A at 600V with Mega-Fit terminals and 12 AWG; 30A peak with Mega-Fit terminals and 10 AWG in a 2-circuit wire-to-wire set
- Circuits
- 2-8 single / 2-12 dual
| Family | Pitch | Max Current* | Wire | Circuits | Use |
|---|---|---|---|---|---|
| Nano-Fit | 2.5mm | 8.0A with 105300 terminals and 20 AWG in a 2-circuit wire-to-board set | 20-26 AWG | 2-8 single / 4-16 dual | Compact signal and power, tight packaging |
| Micro-Fit 3.0 | 3.0mm | 8.5A with 43030 terminal and 18 AWG | 18-30 AWG | 2-12 single / 2-24 dual | Mid-density power and signal workhorse |
| Ultra-Fit | 3.5mm | 14A with 172253 tin terminals and 16 AWG in a 2-circuit single-row wire-to-board set | 16-22 AWG | 2-8 single / 4-16 dual | Compact 600V power with glow-wire options |
| Mini-Fit Jr. | 4.2mm | 9A with 5556 terminal and 24-18 AWG variant; 13A with 45750 HCS terminal and 16 AWG | 16-28 AWG | 2-24 dual | Classic power interconnect |
| Mega-Fit | 5.7mm | 23A at 600V with Mega-Fit terminals and 12 AWG; 30A peak with Mega-Fit terminals and 10 AWG in a 2-circuit wire-to-wire set | 10-16 AWG | 2-8 single / 2-12 dual | High-current power runs |
*Max current is the best case from Molex family data. Real limits come from the exact terminal, wire, circuit count, ambient temperature, and housing selected.
Choose Mini-Fit Jr. when 4.2mm pitch, dual-row power density, board-header support, and broad sourcing are more important than the smaller package of Micro-Fit 3.0 or Nano-Fit. Step up to Mega-Fit when the selected Mega-Fit terminal and heavier wire are required.
The Mini-Fit Jr. limits that matter
Use Mini-Fit Jr. for 4.2mm pitch dual-row power connectors. A 9A circuit requires a 5556 terminal in the 24-18 AWG variant, while a 13A circuit requires a 45750 HCS terminal with 16 AWG wire.
Electrical
- Pitch
- 4.20mm
- Current
- 9A with 5556 terminal and 24-18 AWG variant
- HCS Current
- 13A with 45750 HCS terminal and 16 AWG
- Voltage
- 600V
Mechanical
- Rows
- Dual-row
- Circuits
- 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24
- Mating Cycles
- 30
- Headers
- 5566 vertical, 5569 right-angle, 46999 right-angle with pegs
Environmental
- Temperature
- -40 to 105 C for 5557/5559 housings
- Sealing
- Non-sealed family
- Housing Options
- Natural 94V-2, black 94V-0
Materials
- Receptacle
- 5557 family
- Plug
- 5559 family
- Female Terminal
- 5556, 45750 HCS
- Male Terminal
- 5558, 44476 HCS
Reference data comes from manufacturer CAD models and Molex family catalog data; verify final ratings against the exact selected contact and housing.
Positions, rows, and keying
Mini-Fit Jr. circuit counts
Common 5557 receptacle housing sizes. Mini-Fit Jr. planning is even-only dual-row from 2 through 24 circuits.
2-Circuit
39-01-2020
4-Circuit
39-01-2040
6-Circuit
39-01-206010-Circuit
39-01-2100
16-Circuit
39-01-2160
24-Circuit
39-01-2240
Use the molded housing numbers and the exact connector-side view before assigning circuits. Do not mirror a plug and receptacle face unless the drawing confirms the view.
Rows, panel ears, and intermate rules
Mini-Fit Jr. is a dual-row 4.2mm pitch family with even circuit counts. Select the housing family first, then choose natural or black material options, panel ears when needed, and matching terminal series.
Mini-Fit Jr., Plus, TPA2, and BMI variants can intermate when the exact selected parts support it. Mini-Fit Sr. and other Fit pitches do not intermate.
Mini-Fit Jr. connector stack
What completes a Mini-Fit Jr. connection
A typical wire-to-wire connection pairs a 5557 receptacle with a 5559 plug, then matches 5556 female terminals and 5558 male terminals to the selected wire range.
For board transitions, select the header orientation and retention style before choosing cable exit direction and strain relief.
- Receptacle Housings
- 5557, 39-01-2xx0 natural, 39-03-9xxx blackAccepts 5556 female terminals and pairs with 5559 plugs.
- Plug Housings
- 5559, including 39-01-2021, 39-01-2026, 39-01-2041 panel-ear optionsAccepts 5558 male terminals and pairs with 5557 receptacles.
- Terminals
- 5556 female, 5558 male, 45750 HCS, 44476 HCSMatch terminal to conductor gauge before assigning current.
- Headers
- 5566 vertical, 5569 right-angle, 46999 right-angle with pegsUse for wire-to-board layouts.
Contact and accessory choices
Mini-Fit Jr. terminal choice controls current and wire fit. Use 5556 and 5558 for standard builds, and HCS terminals only where the drawing and wire size support the higher current.
Standard Terminals
- Female
- 5556 into 5557 receptacle
- Male
- 5558 into 5559 plug
- Wire
- 28-16 AWG by terminal variant
- Current
- 9A with 5556 terminal and 24-18 AWG variant
HCS Terminals
- Female
- 45750 Mini-Fit Plus HCS
- Male
- 44476 HCS
- Wire
- 45750 HCS terminal and 16 AWG for 13A condition
- Current
- 13A with 45750 HCS terminal and 16 AWG
For quoting, choose the terminal series first. The housing does not make a 13A circuit unless the 45750 HCS terminal and 16 AWG wire condition is met.
Wire gauge and terminal fit
Mini-Fit Jr. spans 28-16 AWG across terminal variants. The 5556 terminal variant must match the actual conductor size, insulation OD, and crimp tooling.
When current is the reason to choose Mini-Fit Jr., keep the exact terminal and wire condition in the BOM so purchasing does not substitute away the rating.
Wire and fit checks
- Standard Wire
- 28-16 AWG by 5556/5558 variant
- 9A Condition
- 5556 terminal, 24-18 AWG variant
- 13A Condition
- 45750 HCS terminal, 16 AWG
- Rows
- Dual-row only
Final wire choice comes from the exact housing, terminal, insulation OD, bend radius, and bundle temperature. Gauge alone is not enough.
What drives cost
Mini-Fit Jr. cost moves with circuit count, material, terminal family, TPA2 or BMI options, and header orientation.
- Circuit Count
- 2 circuits lower, 24 circuits higherMore cavities add housing, terminal, assembly, and test time.
- Terminal Family
- Standard lower, HCS higherUse HCS only when the 45750 terminal and 16 AWG current condition is required.
- Board Hardware
- Straight lower, right-angle with pegs higherHeaders such as 46999 add retention and board-layout constraints.
Stock and sourcing
MiniProto stocks 93 Mini-Fit Jr. connector entries across 39-01 housings, 39-03 black housings, and 46999 headers in the live configurator catalog. We quote the housing, terminal, header, and optional TPA2 stack together so substitutions do not change fit or current.
Assembly, and the mistakes to avoid
- !Do not treat every Mini-Fit Jr. terminal as higher-current capable. The 13A condition requires a 45750 HCS terminal and 16 AWG wire.
- !Do not specify odd circuit counts. Mini-Fit Jr. planning is even-only dual-row from 2 through 24 circuits.
- !Do not swap 5557 and 5559 roles. 5557 accepts female terminals, while 5559 accepts male terminals.
- !Do not assume Mini-Fit Sr. or another Fit pitch will mate. The pitch and housing series must match.
Common questions
What is Molex Mini-Fit Jr. used for?+
Molex Mini-Fit Jr. is a 4.2mm pitch dual-row power connector family used for power supplies, appliances, non-sealed automotive ECUs, telecom backplanes, fan trays, servers, copiers, printers, and similar equipment.
How much current can Mini-Fit Jr. carry?+
Standard Mini-Fit Jr. current is 9A per contact with a 5556 terminal in the 24-18 AWG variant. The 13A option requires a 45750 Mini-Fit Plus HCS terminal with 16 AWG wire.
What is the difference between 5557 and 5559?+
5557 is the receptacle housing family and accepts 5556 female terminals. 5559 is the plug housing family and accepts 5558 male terminals. They make the wire-to-wire pair.
Which terminals does Mini-Fit Jr. use?+
Common terminals are 5556 female terminals for 5557 receptacles and 5558 male terminals for 5559 plugs. Higher-current builds use 45750 or 44476 HCS terminals with the matching wire range.
Which circuit counts are available?+
Mini-Fit Jr. uses even dual-row circuit counts from 2 through 24: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, and 24 circuits.
Does Mini-Fit Jr. mate with Mini-Fit Sr. or other Fit pitches?+
No. Mini-Fit Jr. is the 4.2mm Fit family. It does not mate with Mini-Fit Sr., Micro-Fit 3.0, Nano-Fit, Mega-Fit, or other pitches.
Build your Molex Mini-Fit Jr. harness
Pick positions, contacts, and wire. See the price as you go, then send it to our floor.