The pins inside that plug that used to be attached to the wire are usually held in with a small tab and once they are in, it's difficult, but not impossible to remove them.

You will need the smallest flathead jeweler's screwdriver you can find, and you will have to hope you have enough room in the connector hole to push that tab in to extract the metal pin out of the connector.

If you can get the pin out you can resolder the wire and then re-insert the pin back into the connector.

 

I have some pin extraction tools I use at work but that would kind of be a waste of money to buy them if you’re only going to use them once. If you can’t get the pin out then you may have to see about finding a new harness. I would imagine they’re not horribly expensive

 

You could also like find a replacement plug from Mouser or Digi-Key but you will have to measure it with a caliper, including the pin spacing.

Both companies provide dimensional drawings from the manufacturer of nearly every hardware and passive device they sell.

 

Same exact failure that I had on mine, I was lucky to catch it before complete separation and soldered then slipped heat shrink over and it worked. If it fails again I'm redoing it as with heat shrink it now is not as flexible as I would like.

You know every Bachman I've ever owned has had some kind of minor failure like this really makes me hesitant to buy any more.

 

This may be a questionable idea since I've no experience with this particular damage, but:
Could you open the loco shell and remove the existing 2-pin socket altogether, extend the stripped wires an inch or so if needed for leeway, and solder them directly to the 2 inner now plug-less wires, running them through the hole where the orange plug was ?...
Then just bear in mind you can no longer separate the tender from the engine (Or, at least, not very far).

Guess I could have just said "Try bypassing the orange plug with direct wiring"....

 

Look along one of the sides of the connector near where the female socket is and you should see some metal part of the connector that might be the release. Unfortunately since the wire has pulled out you can't use the wire to hele pull the pin back out so you may have to push the socket end while pressing on the release on the side. You can get spare pins, but as Michel says just solder the wire back in with now blobs if solder as it will not fit back in! If you can easily get new crimp pins that would be better, but besides the pins (sockets) you will need a good crimping tool that may cost in excess of $20. Crimp tools are somewhat specific and I learned long ago that you can waste you money on cheap crimp tools.

 

Again I must say:
Why not just hardwire it by bypassing the plug ? It'd be a cinch and what's the likelihood you'll ever need to separate the tender from the engine anyway ? You wouldn't even need to solder.. Electric tape or heat shrink could hold the braided wires, since you'll have the draw bar in place as well...Basically those plugs are only present on steam so that one can separate loco from tender.. And even if you did need to some day, so you unbraid the wire you bypassed the plug with, do what's needed, and re-braid them. You still have the other 4 pin plug operating to boot...

 

A bit late to this party, but I have same issue with 2 of the 4 wires in the 4 pin connector. Anyone know what the replacement part might be? Bachmann web site doesn't show much in response to a search. Seems I have a choice of sending the whole thing back for $40 (plus shipping) or trying one of several hacks (as mentioned here). Looking on eBay, seems my Niagara which I got new for about $115 is now going for at least twice that, so $50 bucks for a repair isn't out of the question; but the only way to justify it is to NEVER separate the tender again. I could splice in proper JST connectors that separate easier, but I think the wires would be longer/thicker/uglier.

 

I would simply replace the entire harness with something like this, micro miniture harness, about $2.00 each in the US.

 

thanks, I was able to get the loco powered play forcing the connectors back together with some pin sized probes, but headlight still out - wish there was doc for what each wire was supposed to do; I have done a similar replacement on a different loco but was reluctant to try it on this one because of prior "challenges" working on Bachmann pieces. For now, decided that powering it as well as modifying the box to allow Loco and Tender to stay connected was a good enough for now.