Is the KONNRA KR4200 a drop-in replacement for the Molex Mini-Fit Jr. 4.2mm connector?

Short answer: on the level electrical rows and the mechanical forces it lines up closely. On the three rows that decide a substitution it does not, and the biggest gap is a documentation gap rather than a product gap.

I work on connector and harness programmes at KONNRA, so read that disclosure first: the KR4200 is one of the series I deal with, and I am answering from the manufacturer's side. Every figure below comes from manufacturer documents on both sides; where they disagree, both figures are printed.

The finding that decides the question

The KR4200 is documented twice per interface, with two different ratings, across four product specifications. All four are Edition A1, all four are dated 2022/2/26, and nothing in the file names distinguishes the tiers. Only the contents do.

PS-KR4200-01, wire-to-board, 5A (20AWG) tier, AWG 20# to 24#, insulation 1.10 to 1.80mm, terminal T4200F*T0102A.
PS-KR4200-02, wire-to-board, 9A (16AWG) tier, AWG 16# to 20#, insulation 3.10mm Max., terminal T4200FB***01B.
PS-KR4200-03, wire-to-wire, 5A (20AWG) tier, AWG 20# to 24#, insulation 1.1 to 1.8mm, terminals T4200F*T0102A and T4200MBT0102A.
PS-KR4200-04, wire-to-wire, 9A (16AWG) tier, AWG 16# to 20#, insulation 3.10mm Max., terminals T4200FB***01B and T4200MBT0101A.

The original's own headline maximum is 9A, at AWG #16 or #18 in a two- or three-circuit brass connector. The 9A tier is the one that matches it — same nominal current, same nominal conductor — and it sits in the second document of each interface. So a customer who asks for "the KR4200 specification" and is sent one file has a fifty per cent chance of receiving the tier that does not match the requirement they came with, and neither file's title tells them a second file exists.

The tiers also use different terminal part numbers, so an upgrade from 5A to 9A changes the terminal, the crimp tooling and the applicator settings, not just the box label.

A 600V rating carrying a 1,500V test level

A dielectric withstanding voltage test is not a second rating, but it is not decorative either: it establishes that the insulation system survives a fault-level overvoltage for a defined period without breaking down, and the level a manufacturer chooses is normally derived from its own rated voltage by a fixed rule.

Molex publishes 2,200 VAC for 1 minute with no breakdown and leakage under 5 mA. At its own 600V rating, that is exactly two times the rated voltage plus 1,000 volts:

2 × 600 + 1000 = 2200

Run it at 250V and it yields 1,500V; run it at 600V and it yields 2,200V. The two results are 700V apart, and our 1,500V test level appears at both ratings.

All four KR4200 specifications publish 1500V AC for one minute between adjacent terminals or ground, per EIA-364-20A. Our figure is not a transcription error — it is a house figure, and the evidence is that the same 1,500V value appears in our 250V-rated 3.00mm, 3.96mm wire-to-board and 3.96mm board-in specifications as well. One number carried across series reads as a documentation convention; one number derived per series from that series' own rating reads as a derivation.

Two qualifications belong with that. This does not mean the connector fails a 2,200V test — no such result is published on either side. It does mean that a qualification programme taking the original's dielectric row as its acceptance criterion will find our published value 700V short, which is a document request rather than a substitution decision. And the original's own older, variant-specific flange document publishes 1500V AC(rms) for one minute on a part that also carries a 600V rating, so the original's document set contains both a 1,500V and a 2,200V level at 600V, and I print both rather than choosing.

Temperature: split by base metal on one side, open on ours

Molex splits its temperature ranges by the contact's base metal: brass −40°C to +80°C and phosphor bronze −40°C to +105°C, with the footnote "Including 30°C terminal temperature at rated current".

We publish one figure: all four specifications state −40 to +105°C, and the terminal component page states −40°C to 105°C. The figure is consistent across our documentation; the problem is the material it is claimed for. Our materials section reads "Terminal: Phosphor Bronze/Brass Tin Plated Over Nickel" and the wafer entry reads Contact: Brass Tin Plated Over Nickel — it does not choose a metal, it lists both. Our cross-reference page, meanwhile, calls every terminal brass: T4200FBT0102A and T4200FBT0104B on the female side, T4200MBT0102A and T4200MBT0101A on the male side, four rows out of four.

So the temperature row has two readings and both must be printed:

If the terminal is brass, our +105°C exceeds the original's own brass ceiling by 25°C.
If it is phosphor bronze, our +105°C matches the original's phosphor bronze figure exactly.

Only one of those readings is safe, and which applies depends on an unfilled field in our own document.

There is a counter-intuitive half that the original's own table publishes. At AWG #16 and #18, in a two- or three-circuit connector, brass is rated 9A and phosphor bronze 8A — brass is the better metal for current. Against the temperature rows the two metals swap places, because phosphor bronze reaches +105°C and brass only +80°C. Neither metal is simply better, so a requirement of 9A at 18 AWG in a three-circuit connector above +80°C is not satisfied by one metal on the original's side either: it takes brass for the current row and phosphor bronze for the temperature row, and at 18 AWG in three circuits phosphor bronze is rated 8A rather than 9A. The trade exists on both sides; the difference is that the original documents it and we currently leave it open.

Where we genuinely line up

The level rows are a match, which is why this cross-reference is worth writing.

Contact resistance, initial: 10 milliohms maximum on both sides, our clause naming a dry circuit at 20mV and 100mA per EIA-364-23C.
Insulation resistance: 1000 Megohms minimum at 500V DC on both sides.
Durability: 30 cycles at 10 cycles per minute, with 20 milliohms maximum change from initial.
Temperature rise 30°C; heat resistance 96 hours at 105 ± 2°C; cold resistance 96 hours at −40°C, the original at ± 3°C and ours at ± 2°C.
Per-circuit insertion maximum 14.71 N against the original's 14.7 N, agreement to within 0.01 N. Per-circuit withdrawal minimum 0.98 N at first mate against 0.5 N, so our guaranteed floor is about double the original's before the thirtieth-cycle decay.

Three mechanical figures also land within about two per cent: insertion 1.5 kgf (14.7 N) against 15.0 N, retention 3.0 kgf (29.4 N) against 30 N, pin retention 1.0 kgf (9.8 N) against 9.81 N.

The honest limits

We do not cover 26 or 28 AWG on either tier. Our 5A tier starts at 20# and our 9A tier at 16#, while the original runs to 28 AWG with published currents of 2A for brass and 1A for phosphor bronze at 28 AWG and an insulation window of 1.80mm for its fine-wire group. A fine-wire harness is a coverage question, not a cross-reference question.
The 5A tier's 1.80mm insulation ceiling is far tighter than the original's 3.10mm for 18 to 24 AWG — a gap of 1.30mm — so a 20 AWG wire with 2.5mm of insulation passes the original and fails the tier most customers are sent first.
Post-humidity insulation resistance is 100 megohms minimum on our side against the original's 1,000 megohms, and the same post-humidity figure appears across our 2.5mm to 4.20mm specifications, so it is a house clause.
At 20 AWG our published figure is 5A against the original's 7A for brass and 6A for phosphor bronze, and our 9A tier states its rating as the tier's 9A (16AWG) figure rather than as a per-gauge table, so it cannot be read as a derating curve. Where we publish one number and the original publishes a grid, the honest comparison is at the grid's cell, not the tier's label.
The original publishes rows we do not: agency files with numbers (UL File E29179, CSA Certificate LR 19980, IEC 61984, plus a per-series table showing UL 600V, CSA 600V and IEC 250V, where we publish UL E482542 only); glow-wire data on eight named series to EN 60695-2-11 / IEC 60695-2-11 with an EN 60335-1 / IEC 60335-1 750°C for 2 seconds, no flaming investigation; normal-force limits of 1.47 N (150 grams) for tin and 0.49 N (50 grams) for gold; panel and latch forces, from 225 N maximum panel insertion and 157 N dual row / 133 N single row minimum panel withdrawal to a 22.24 N (5.0 lbf) maximum thumb latch operation force and 68 N (15.3 lbf) minimum thumb latch yield strength; and a 56-cell current table organised as two base metals by seven gauges by four circuit bands.

Two things I found on our own side

The terminal component page for the wire-to-board female terminal publishes Current (Max) 9A paired with Wire/Cable Size (AWG) 18#-22# and Insulation Diameter 2.50mm (MAX). That combination appears in none of the four specifications, which publish 20# to 24# with 1.10 to 1.80mm and 16# to 20# with 3.10mm Max., and a media asset in our own library is titled "KR4200 4.2mm Pitch 5A current single or dual row connector", publishing the low tier in a file name. So a buyer can find 5A or 9A, and one of three wire windows, depending on which page they open.

The cross-reference page maps a single KONNRA part number to two Molex references whose own descriptions contradict each other: H4200F2111602A appears for both 5559-22P (with wings, clear) and 5559-22P1 (without wings, clear), and H4200F2121602A for both 5559-24P and 5559-24P1, where the suffix difference is exactly the wings. It also maps H4200M2011601A to both 5557-02R and 5557-02R-210, two different flammability grades in the original's own document.

So, drop-in or not?

If your requirement sits inside the level rows, the two parts behave the same on paper. If it sits on the dielectric row, the temperature ceiling, the 20 AWG current cell or the fine-wire end of the range, the answer is not yet. Name the tier, the terminal part number, the base metal, the conductor and the insulation diameter — five fields where the comparison is decided, and four that cannot be read off a cross-reference page.

Two links, if you want to start from our side:

https://konnra.com/molex-5557-cross-reference-kr4200-mx4-2-connector-guide/
Dongguan Konnra Electronics Co., Ltd