Just wondering if anyone has any tips and tricks for assembling these molex connectors. The pins are sooooo small I can barely see what I’m doing. Do they need to be soldered also or just crimped? what orientation do they go into the connector?

Also, what is the part name or number for the double connectors like this, the one’s used for the fans, I forgot to order those :slight_smile:

I do LOTS of these. I use a crimping tool, that makes it a lot easier and more reliable. I’ve seen lots of issues with intermittent connections when folks try to crimp these with needle nose pliers. Best to save the headache and get the right tool. You’ll smile every time you use it.

If you look at the terminal (the metal pin part) you will see a very tiny tab that lifts up away from the shaft. That tab fits in the slot on the backside of the connector. You will hear and feel a “Click” when it seats into the connector.

Lulzbot publishes the bill go materials (BOM) for all of their printers on their support site->Source. The Mole part # and the Mouser and Digi-Key part numbers. Best to go look at that and you’ll learn all kinds of other useful things to boot!

I ALWAYS solder molex connectors! Believe me if you spend the time to assemble it all up and then one of the wires pulls from the pin, then you spend the time to get the pin out without a molex removal tool–they are specific to the type of connector–or spend the time waiting for the removal tool to get shipped because you don’t already have one. You will end up just cutting the whole connector off and starting from scratch. :angry:

Then you suddenly realize that you didn’t buy enough extra pins to rebuild another connector! :imp: So you have to wait for those to get shipped and a 10 minute job ends up taking you a whole week to finish. :smiling_imp:

Just solder them in, it’s super worth the little extra time. Plus then you don’t need to buy the molex crimping tool. And you don’t have to worry about faulty connections.

This is all-of course–assuming you already have a soldering iron and decent soldering skills and don’t assemble connectors often so you don’t have all of the tools and stocks of extra pins and connectors lying around.
Here’s a little write up I did when I got my e3d nozzle.
Look for my post on page 3. I have links to mouser for all the connectors and pins needed–so you don’t have to search around–plus a little how to on soldering and hooking up the connectors.

I made lots of different connectors when I was a mechanic, spent all the money on a couple handfuls of crimping tools and removal tools–molex, packard, deutsch, other brands–and I came to find that soldering was the best way to go.

they’re just so small, it’s a little intimidating. I do a lot of soldering for rc stuff that’s pretty small but this is about the smallest I’ve done so far, I think I’ll crimp AND solder…I already have the crimping tool and all the soldering supplies.

thanks for the info gents, helps a lot. Brew, I’ll check out your link also.

The best way to solder them is to tin the wire so there aren’t strands going everywhere and so flow to the wire is not an issue. Crimp the wire into the connector–I forgot to mention that I crimp them as well, else they won’t go into the connector housing. Then put a small pin drop of flux on the connector where you made the crimp to the wire. Tin your iron with a tiny amount of solder–you can always add more. Then lay the iron on for 1-1.5 seconds, which about when the flux will stop sizzling. When in person I teach that saying the word “half” takes about half a second. So hold the iron on for 2-3 “halfs”. Then check that the retainer spring is not soldered up.

The biggest worry about soldering the connectors is having solder flow up to the retainer spring(s). You could always try it with a spare pin and scrap piece of wire to get the timing down if you’re really nervous about it.

Last aside: for anyone who doesn’t want to solder to the pin just solder the stranded wire before crimping it to the connector. It will give the crimp tabs something more solid to sink into and hold onto.

ok, I’ll give it a shot.
Suuuuuuch a PIA job though…ugh. :frowning:

How much wire do I leave exposed, am I pushing the wire right up to the end of the pin, ie, fill the hole pin with exposed wire or is there some other technique?

thanks for all the insight though. 'ppreciate it.

I too crimp (using the ratcheting crimper) and solder.

You have to be careful with the soldering. Too much and you wont be able to get the pin into the housing.

Pololu sells pre-crimped wires.


Crimping is definitely a major pain, but critical (and hard to debug!). The hand tool crimper listed above will work well. You don’t need to solder if you use a crimper like that. If you’re doing them by hand, it might not be bad to drop solder in there, if you don’t have a crimp tool.

For what it’s worth, we use machines like this:


If you solder, don’t use too much. It will impede the pin from sliding into the plug, or it could block the tab spring mechanism. Maybe tin the wire and heat the pin with the iron for a good connection.

I crimp the ends for my RC stuff… it took me a bit to get the hang of it. Buy some spare ends and practice. Give a good yank to make sure they are on tight. :slight_smile: I use the same ratcheting tool mhackney posted. For me it was easier to insert the pin on the back side:

  • Squeeze one click of the ratchet
  • Insert the pin up to the tabs that grip the insulation.
  • Strip the wire and insert wire into pin (still held by the tool, helps to pre-measure the insulation)
  • Squeeze fully to crimp the wire
  • Use needle nose pliers to crimp the tabs on the insulation, or use the ratchet crimper but only squeeze half way (release ratchet manually).
  • A small dab of solder at the base.

In any case, you’ll figure out what works best for you… just buy extra pins. :slight_smile:

Everyone here has really good posts. I hope I didn’t open up a can of worms suggesting the use of solder. It’s just something I learned being a diesel mechanic. Just crimping will never withstand 10 years of semi truck vibration.

I think the key everyone seems to be leading to with these small pins and connectors is that there isn’t room for excess. I only strip the wires back far enought to get them just past the crimp point, no more. Same with soldering just enough solder and just enough heat to get it to weld up, no more.

Finding out how much is just enough is the PIA, and it takes a little practice.

for sure, it’s really appreciated.

ooofff, think I’m going to need to see pictures though… so the wire insulation should just sit in the first little set of arms then? the bare wire can run a little further up the pin?

Also, the pre-crimped connectors on Pololu don’t seem to have the little “clicker” tab on them? What keeps them from coming out once you insert it into the housing?

Here are a couple of photos that I already have of connectors that I soldered. I’ll make a couple of youTube videos tomorrow of the whole process so you can get a better feel for the timing and whatnot.

So yeah the first/big crimp area is for the insulation and the second/small crimp area is for the stripped wire. I hope it helps, if not just wait for my video tomorrow I promise to post it as soon as I get my first cup of coffee. :smiley:

The lighting is rough but you can at least make out that the solder does not extend past the wire and the wire does not extend much further than the crimp area.

Oh man, that helps so much!! awesome! I see exactly how it’s supposed to work now, thought the wire had to go to the end of the pin, but it’s only being held in by a short amount, I see why you’re keen on soldering it now :slight_smile:

Did you read my question about pololu pre-crimped connectors? what do you think? They don’t seem to have the little tab that locks it into place.

Yeah they seem a bit different, maybe they are for a similar but slightly different housing IDK. I usually go with Mouser for all of my electronics–I probably spend ~$5,000 a year with my company there so I have a good report with their sales rep.

The crimp on the wires looks good though, at least in this picture.

Yep. but if they don’t lock into place…all the solder in the world won’t keep them from sliding out. There’s probably some other way they stick in. Maybe I’ll give them a call and find out. Thanks for all the pictures Brew, at least I have a little bit of an idea of what it’s supposed to look like.

While they don’t show how to deal with molex connectors, the NASA standards are a good read for general connector/soldering/etc info:

LOL…pretty much covers…EVERY single possible way.

I don’t think I could justify this to the wifey… :wink:

Show her that, then show her the great deal you’re getting on: