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Darkbmwlord

Wiring help

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I'd like to tackle repairing the wiring at the boot lid, as you can see I think someone has been there before!:huh:

 Hopefully it might fix the flickering of the number plate lights.

 

I'm afraid I don't know much about wiring - could an expert tell me what kind of wire to buy? I don't want to use too heavy or too light for the current and cause a fire!

 

Many thanks for your help.

IMG_20171020_123142.jpg

Edited by Darkbmwlord
Forgot photo

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You may not need any cable at all. I used this type of pre-soldered connector when I last did this job - http://www.ebay.co.uk/itm/Assortment-of-50solder-joints-most-popular-sizes-are-presorted/263131501524?_trkparms=ao%3D1%26asc%3D20170912101845%26meid%3Df540744cdcfc4113b2c57ad8f5484962%26pid%3D100705%26rk%3D1%26rkt%3D1%26&_trksid=p2045573.c100705.m4780

 

That's not necessarily the cheapest/best, just the first link I found.

 

That made the job easy, cheap and they're not bulky either. Just buy some loom tape to cover it all up with once you're done. 

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I went and pulled a loom out of a breaker, that way you get plenty of wire (obviously don’t use the same part where it’s cracked). You also have to decide if you solder or crimp of course.

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3 hours ago, Hairyarse said:

You may not need any cable at all. I used this type of pre-soldered connector when I last did this job - http://www.ebay.co.uk/itm/Assortment-of-50solder-joints-most-popular-sizes-are-presorted/263131501524?_trkparms=ao%3D1%26asc%3D20170912101845%26meid%3Df540744cdcfc4113b2c57ad8f5484962%26pid%3D100705%26rk%3D1%26rkt%3D1%26&_trksid=p2045573.c100705.m4780

 

That's not necessarily the cheapest/best, just the first link I found.

 

That made the job easy, cheap and they're not bulky either. Just buy some loom tape to cover it all up with once you're done. 

Do you just crimp those on?

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I would resolder the wires with the correct gauge, using a lineman splice (nice video showing how to do it below). Then put on heat shrink and a new shroud. Never trust those sorts of connectors.

 

 

 

 

 

 

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3 minutes ago, Clavurion said:

Unfortunately Nasa standards have nothing to do with automotive connections. Crimped wire connector is much more resilient to constant resonances and bending than solder joint.

 

Fair enough.. I think I just enjoy soldering things too much.

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2 hours ago, Darkbmwlord said:

Do you just crimp those on?

 

No just heat them gently to melt the solder. I used a hot air gun, with a thick, rubber type tile behind the wires so I didn't heat the car/paint itself!! Easy job, took no time at all really. Well it did, but quick relatively speaking! lol

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Those pre soldered connectors look interesting.I have never seen them before and I must confess that over the years I have had mixed results when splicing wires with solder joints. Worth looking to see if you can get a lesser quantity for a lower price. 

In view of some of the comments on the sellers feedback (which is not too good) I checked Amazon. They list these connectors but are currently out of stock

Edited by stevecvo
Extra info

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never had any probs with crimped connectors in auto wiring or 240v just use quility ones and a good crimping tool

in my day job i use crimped conectors on many repair jobs and tec mod jobs  and the specks for the mod are devised by our qc dept

on 12v crimps i also cover joint with heat shink and if a few wires in the loom i stagger joints then rewrap with loom cloth tape

just done a chunk of loom in my boys freelander tailgate with no issues .

and 3y ago the retro fit electric & heated seats mod and all good still.

 

 

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On 10/20/2017 at 4:00 PM, Hairyarse said:

You may not need any cable at all. I used this type of pre-soldered connector when I last did this job - http://www.ebay.co.uk/itm/Assortment-of-50solder-joints-most-popular-sizes-are-presorted/263131501524?_trkparms=ao%3D1%26asc%3D20170912101845%26meid%3Df540744cdcfc4113b2c57ad8f5484962%26pid%3D100705%26rk%3D1%26rkt%3D1%26&_trksid=p2045573.c100705.m4780

 

That's not necessarily the cheapest/best, just the first link I found.

 

That made the job easy, cheap and they're not bulky either. Just buy some loom tape to cover it all up with once you're done. 

 

I did a similar job on our 330 Ci, and found there was enough wire to solder and heatshrink. However, its quite tight working with so many wires in the same place, so I like the look of the product in the link as this holds the wires in place whilst heat is applied, as that is the difficult part. You need to keep each repaired joint as narrow as possible otherwise you finish up large bulge in the loom.

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On 10/21/2017 at 7:49 AM, Clavurion said:

Unfortunately Nasa standards have nothing to do with automotive connections. Crimped wire connector is much more resilient to constant resonances and bending than solder joint.

 

Especially that you tube one, where the solder has wicked up the wire, making it hard and break-prone!

 

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Solder is good, crimp is good. But... if you solder, you need to smear flux (regular type, not the 'no-clean' etc. variety) on all surfaces and wires to be soldered. A good quality soldering gun (ideally temperature controlled) would help, but it's not as important as the flux. Crimping is only good it you use a dedicated crimping tool. With a proper crimp, wire will break before you can pull it out of the terminal. For red/blue/yellow insulated spade connectors, you would need a ratchet crimper as pictured.

 

crimp.jpg

Edited by Tomcat

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I've suffered from broken wires in this trunk harness too. The problem is caused by flexing as the lid is opened and closed - eventually the flexing causes fractures in the strands. By all appearances it wasn't vibration causing the failures.

 

BMW uses very thin strand wiring for these leads: at least twice the # of strands compared to "standard" wiring of the same gauge. The thin strands tolerate flexing much better. But I found that in both open circuit wires the break point coincided with cracks in the insulation jacket which then seemed to have concentrated the the flex to a sharp radius and accelerated  the strand fatigue. I also found several other insulation breaks where the wires strands hadn't yet all broken, but were close. So I strongly suspect the jacket cracked first which then concentrated the flex point to a sharp radius and concentrated flexing broke the strands. Probably a case of plastic aging and losing flexibility. I suspect that Ontario winter temperatures that makes the plastic insulation hard & more brittle played a part too.

 

I first looked at specialized high flex wire which comes with crack resistant silicone rubber insulation. But everything I could find had quite a thick insulation jacket with too large an OD; I wouldn't have been able to get the 13 (IIRC) leads through the boot/snorkel. I rejected the idea of any repair joints (crimped or soldered) inside the boot since both ends of each would become flex concentration points and led to premature failure again.

 

 In the end I salvaged a complete harness from an auto wrecker. The repair has lasted 4 years to date ... & I'm keeping my fingers crossed. If I'd been aware of the repair kit listed above I'd have probably gone that way on the notion that new insulation would tolerate flex better than older, recycled wire.

 

Regards

RDL

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Like you suspected insulation is the main problem. Silicone insulation for the same voltage is thicker than regular insulation materials. Cables for industrial robotics would be best for this purpose. They are designed for continuous bending. 

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