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 Post subject: Soldered joints
PostPosted: Mon Dec 21, 2015 9:05 pm 
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Had my daughters mgzt 1.8 in last week to do some jobs on.
After starting and running on petrol, the changeover brought a continious "beeeeeep" from the sounder.
I hooked my laptop up - gas temperature sensor fault.
So a simple wiring check found the loom had been soldered to the sensor wires, very neatly, with heatshrink sleeves over each joint - i say each joint, because pretty much all the joints had been done this way, except for the gas injectors.
Anyway, a pull on the gas temp wires found one of them pull apart, the ends corroded to a green dust.
Another reason never to solder joints, it backs up my previous experience of such joints, over many years. Now to replace all the others, don't know what with though?
Huw


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 Post subject: Re: Soldered joints
PostPosted: Tue Dec 22, 2015 10:47 am 
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Soldered joints are fine, if the cable insulation is waterproof, e.g. silicone or PTFE but not necessarily PVC, AND if you use adhesive lined heat-shrink sleeving - or failing that if you use ACF-50 on electrics etc.

Crimped joints are gas tight and free from flux etc, so probably more robust, and crimped inside waterproof connectors (which pass the insulation through gaskets) could be a good way to join wires.

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 Post subject: Re: Soldered joints
PostPosted: Tue Dec 22, 2015 7:06 pm 
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Location: Yorkshire
I solder all connections, even solder wires into spade connectors and battery connectors etc.

Fixed no end of installs where other installers have recommended owner comes to me because they only work on a narrow range of LPG systems and they know I work on them all.. So installer who sent owner to me hasn't even looked at the job before sending owner to me, then when I see the car, first thing I see is a snapped wire to battery connection or I find I can just touch a wire going into a heat shrinked joint and it falls apart at the joint! 'Pfftt thanks mate, I wish I'd seen that or other installer had seen that, how much?'. 'Free mate, or a £fiver cos it took me ten mins to spot.. Could have been prevented if original installer had soldered, then you wouldn't have corrosion in the crimp / could have been prevented if installer hadn't been so obsessed with heat shrink, which caused the snapped wire, had taped instead' :lol:

Crimp or solder is OK as long as there is no water (or humid air) entry.

I used to use heat shrink on everything but these days I usually prefer a good tape (or heat shrink with decent tape around the heat shrink). Too often I've seen vehicles where wiring looks OK, where installer seems to have gone to some lengths to heat shrink wires but heat shrink has turned out a negative regards reliability instead of a positive... Wires have snapped internally at the point at which they enter the heat shrink due to metal fatigue at that point, sometimes possible just to pull the wire out the heat shrink because the wire is so weakened at that point. In the real world, a proper tight wrap with appropriate tape is every bit as good as heat shrink at preventing water entry while tape avoids wires failing due to metal fatigue from flexing at a stress point (because taping can be done in a way in which relieves rather than causes stress points)... Especially regards short wires (and short is often the case when connecting near ECUs, injectors, etc), where heat shrink is even more likely to create acute wire flex points - can be essentially like putting a hard spring into the short wire while making the short wires even shorter, the short wire being tight under that effective spring tension, the stress mostly effecting where wire enters heat shrink. In these cases using tape allows wire to be shorter, neater, less chance of internal breaks.. tape can be built up thicker in middle and gradually tail off to same thickness of original wire = no acute stress points... Same idea as household mains vacuum cleaner etc plugs that have some support for the wire where it enters the plug.

Some may throw their hands in the air reading the above, I might have agree at one time but I'm going on experience.. Even when heat shrinking doesn't mean there is a stress point on wires (again I'll say which can mean wire failure due to metal fatigue), I don't rate heat shrink as any better than tape. Good tape is designed for the job, will last many years (seen good taped joints that have remained water ingress free while under vehicles for 15 years), such tape less likely to crack (immediately or in time) exposing metal than heat shrink (seen a lot of heat shrinks that have cracked open).

I look after LPG systems on a large fleet of limo's, they employ mechanics full time to look after them but I do all the LPG stuff. Mechanics are often changing engines etc (it is a very large limo firm - picture a supermarket car park full of all types of Limos, must be £multi-millions worth, most Rollers are kept outside because the most expensive limos are kept inside!). Mechanics say things like ' Had to cut that wire to take engine out but reconnected properly with a spade connector afterwards'... I advise them not to use spade connectors but to solder and tape or solder and heat shrink instead - crimped spades invariably allow water and/or humid air ingress and connection invariably fails in time, there is no telling whether electrical connection will fail first between the spade plugs (can maybe be avoided altogether with sheathed spades) or at the crimp (can't be totally avoided but can be helped by soldering wire into spade and helped further by heat shrinking or taping around that soldered joint, and as above, preferably taped).

Simon

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 Post subject: Soldered joints
PostPosted: Tue Dec 22, 2015 8:16 pm 
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Yep, I'd agree with that Simon. Used to work installing all manner of controllers on tractors and combines and they were usually used on all manner of noxious chemicals. I never had an installation fail due to a soldered joint. (Usually due to some farmer filling the controller full of water or disconnecting and implement and not disconnecting the wiring....)


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 Post subject: Re: Soldered joints
PostPosted: Tue Dec 22, 2015 9:42 pm 
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There is a range of crimp connectors that are the "Rolls-Royce" of connectors but sadly carry that kind of price tag too. Basically once the crimped joint is made, you blast them with a heat gun. This results first in the outer insulation shrinking and secondly in some solder to flow internally, both soldering and heat-shrinking (with adhesive lining to prevent water ingress) and strengthening the joint. Not even sure if they are still available but i'm thinking they were something like PIDG crimps - long time ago since i used/last saw them.

Alternatively as Simon rightly points out, using heatshrink can at times introduce stress fractures in the cable due to excessive angles etc. Far better to make a loop of cable to prevent an extra tight bend althoough this can sometimes look scruffy. That said it will be infinitely more reliable than an ultra-neat but tight connection.

As for using tape to seal joints, it's perfectly feasible to do that. Many moons ago i worked on some dredging ships and the dredging boom had angle sensors in. These sensors would often fail and the Eex enclosure they were mounted in had to be opened up, the cable removed and the sensor replaced and then the cable entry sealed to prevent water ingress 30+m under the sea. Although there was a cable gland for strain relief, this wouldn't protect against water ingress at that depth. This was achieved with self amalgamating tape followed by insulation tape to seal it all. I only came across one waterogged sensor and i'm happy to say it wasn't previously sealed by me! So it can be done effectively.

The bottom line is it's best to use whatever protection best serves the installation and as much of it as is practicable. This varies with the connection being made but a rule of thumb is no tight bends, stretched wiring or strapping everything together with cable ties so it pulls on the cables - leave some sort of loop for a bit of give, especially on an engine which can rock slightly when revved and/or under load.

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 Post subject: Re: Soldered joints
PostPosted: Wed Dec 23, 2015 10:20 am 
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I used self amalgamating tape to protect joints in Co-Ax used for external WiFi antennas, would you recommend it for automotive use? I'm a bit concerned about it having the correct resistance to heat. (otherwise, it's almost magic!).


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 Post subject: Re: Soldered joints
PostPosted: Wed Dec 23, 2015 11:15 am 
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Joined: Tue Aug 26, 2014 1:48 pm
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Location: South end of North Yorkshire
The spec sheet for the cheap stuff RS sell states -95C to +95C temperature range. The silicone based ones (eg 3M) go up to 180C so would be fine anywhere on a car as long as it's not too near any exhaust components. I've used it to repair a split radiator hose with no issues.

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 Post subject: Re: Soldered joints
PostPosted: Wed Dec 23, 2015 1:54 pm 
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Fantastic :)
No more heat shrink for my Jeep then. I repaired some of the driver's door wiring loom with solder/heat shrink and some of the cables have died after about year. This time I'll use self amalgamating tape instead.


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 Post subject: Re: Soldered joints
PostPosted: Wed Dec 23, 2015 5:21 pm 
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Morat wrote:
Fantastic :)
No more heat shrink for my Jeep then. I repaired some of the driver's door wiring loom with solder/heat shrink and some of the cables have died after about year. This time I'll use self amalgamating tape instead.


I suspect that might be because Jeep used cheap cable in the first place, hence needing the original repair.

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 Post subject: Re: Soldered joints
PostPosted: Wed Dec 23, 2015 9:34 pm 
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LairdScooby wrote:
Morat wrote:
Fantastic :)
No more heat shrink for my Jeep then. I repaired some of the driver's door wiring loom with solder/heat shrink and some of the cables have died after about year. This time I'll use self amalgamating tape instead.


I suspect that might be because Jeep used cheap cable in the first place, hence needing the original repair.


Well, I thought my post above might have caused a bit of backlash but everyone's agreed or been neutral so far. As implied, for the few years after I'd first started in this game (over 10 years ago now) I too thought it seemed obvious best practice to heat shrink... I used to use those little OMVL supplied wire connection tubes that you were supposed to crimp or solder too (I soldered). Then I went out of my way to learn as much about LPG systems / components as I could - Whenever a customer said on phone I have X system with Y fault can you have a look at it I'd buy X interface cable and get wiring diagrams, software, etc thus not make any money on that job but further my understanding of that system by playing with it when it came in. Often found broken wires entering heat shrinks on vehicles others had converted. Would see quite a few where wires had obviously been pulled tight due to using heat shrink so the installer should have known there'd eventually be a problem, but very often it would be difficult to fault the installer for using heat shrink in the given situation, they too seemingly following what seemed best practice by using heat shrink.

Further thoughts on heat-shrink - Yes it can get very hot in engine bays, hot enough to shrink the heat shrink, maybe leading to further shrinking and cracking after the installer has inspected what he thinks is the result of his work.

Regards the Jeep, would expect problem to be due to snapped wires entering heat shrink (wire flex when opening / closing doors causing fatigue at that point). Plenty manufacturers use what amounts to cable ties (loom tidy / holding clips) for wiring looms, even Bentley and Roller. More recent model Chrysler (and a few other makes) seem to suffer electrical gremlins such as door open warnings, none working windows, locks, etc, due to canbus related problems (faulty canbus connected sensors or faulty canbus to doors). Can lose all main door electrical functions if canbus connection to door goes down.

Simon

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http://www.Lpgc.co.uk
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 Post subject: Re: Soldered joints
PostPosted: Thu Dec 24, 2015 7:46 am 
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Location: South end of North Yorkshire
I guess the thing with heat shrink tubing is that it needs to be long enough to provide strain relief, rather than just being about insulating the joint. It's far easier to provide that level of strain relief with tape due to it being thicker, and if wound tight enough it can provide the same level of insulation and waterproofing. I do find heatshrink very good at reparing worn patches on our plastic coated washing line :)

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 Post subject: Re: Soldered joints
PostPosted: Thu Dec 24, 2015 12:49 pm 
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The ‘crush’ crimping that can be often be seen in ‘home mechanics’ repairs should be avoided at all costs. These are often sold as ‘insulated crimps’.

Whilst high quality, ‘figure of 3’ (IE half a figure of 8) crimping is available for insulated crimps, the best ones still seem to be uninsulated.

Whilst soldering forms very solid and trustworthy connections, the lack of flexibility can cause failure next to the solder. As the solder may have run for some distance under the insulation, the user may think the joint is adequately supported when the solder has actually run far past where the user intended.

If the person making the joint is inexperienced (or cost is the major concern) then I’d recommend solder every time.

If the person is regularly involved in wiring and fully understands the mechanical and electrical feature of a professional (figure of 3) crimp (and the budget will stretch) then I’d always recommend a crimp.

You won’t find soldered flexible cables in the air. The closest will be a crimp on the end of the flexible cable where the crimp is soldered (but not to the cable end).
Even my home crimping kit was costly but it does include the kind of crimpers that don’t cause blisters and all the necessary pins and picks to dissemble multi pin connectors.

When I’ve had no choice but to use the ‘crush crimps’, I’ve removed the insulation and inner cable crimp, soldering what remains of the connector on to the lead – Yee Hah, She’ll hold & Near enough is good enough.

Quick thought on tape – self amalgamating is great but can be bulky and inflexible. My personal favourite (for cars) is a good quality insulation tape for repairing insulation then a cloth loom tape over the top. Allowing air in seems to result in less corrosion than sealing the loom (inevitably with a little moisture inside).

Merry Christmas and here’s hoping no one receives a crush crimp kit from Santa or a pack of 5 ‘just like Dads’ 5m insulation tapes.


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