I'm not really sure what the type of plug on the heater cable is. Is it a Molex KK or maybe a JST PH?

The printer is a Prusa I3 Hephestos (aka BQ Hephestos). It came with this "BQ HOT-END HEATCORE CLASSIC" hotend from the "BQ Witbox 1" extruder.

Hotend in question

  • $\begingroup$ Done. But why should this help identifying the plug? If someone knows the molex or JST plug the image should be enough I think. $\endgroup$ Sep 2 '20 at 13:38
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    $\begingroup$ It might help someone with access to documentation for that printer look up the answer for you. Then again, it might not - but additional, relevant information is usually helpful. Welcome to the site, and please take the tour. $\endgroup$
    – Davo
    Sep 2 '20 at 13:41
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    $\begingroup$ The cable of the heater element uses a "JST male connector 2.5 mm pitch". According to the seller of the heater element. $\endgroup$
    – 0scar
    Sep 2 '20 at 14:42

As 0scar noted, this looks suspiciously like a JST connector, but the left one is not a JST RCY connector and it is neither one of the common JST PH nor JST XH, JST manufacturer pages show. In fact, it's not a wire-to-wire JST connector. The BQ-store claims it is a 2.5 mm JST connector, but JST has some 10 dozen different types of connectors, some three dozen of them with a 2.5 mm pitch.

"JST Quick" / JST RCY

enter image description here

This one is rated 3A, and looks like the connector on the right, the thermistor one. So if you need to fix that, you know what to get for that.

So what it is?

The connector however looks at first glance suspiciously like this one: enter image description here

I found this product on several warehouses, listed as 2-PIN CONNECTOR W/HEADER, .10", and even found a specsheet. Those products appear, in design, to be based on the Molex KK 254 from the 2659 series. A genuine Molex 2659-series connector is rated for up to 2.5 Ampere, and looks somewhat similar.

However, the shop did claim it is a JST 2.5 mm pin, and they give a side view:

enter image description here

That is not a Molex KK. It appears more similar to a JST NV, which however has a 5 mm distance between the peg centers (= pitch) and it's rated for 10 A (or 120 W at 12V!). While matching in style it does not match in measurements - as OP confirmed, there's a very close to a 4 mm pitch (+- measurement tollerance) on the connector. So it's not an NV, but something os similar style.

enter image description here

But then it has to be the VH! The VH series has a 3.98 mm pitch, it has that latch and it is rated 10 A, for 120 W at 12 V. In fact, the pins on the Hotend seem to be B2P-VH, matching VHR-2N or VHR-2M "female" adapters.

enter image description here


I would not trust a Molex KK 2659-series connector with a heater cartridge on a 12 V Machine! With a 12 V, 30 W Heater cartridge draws exactly 2.5 Ampere, so you'd have a safety margin of 0! That's bad design. A 40 W heater cartridge would draw 3.3 A - that's 132 % of the rating! That'd be a fire waiting to happen!

Only a 24 V machine could be built with a Molek KK 2659 connector and stay within the 2.5 A rating (40 W & 24 V -> 1.67 A, 30 W & 24 W -> 1.25 A) with a safety factor of about 1.5 to 2 to the rating (depending on heater cartridge).

However, this is a JST VH with a rating of 10 A. That means, at 12 V, it's safe for 120 W load, so plenty safe: That's a safety facor of 3, and on a 24 V machine it'd be 6. That's Perfectly safe and sane! After all we look for at least a 5 A rated connector in conjunction with a 12 V/40 W heater.

The more tedious variant to connect safely is to use either an even higher rated connector (requiring replacement) or a continuous wire to the board.


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