Automotive/low voltage Splicing and Tapping (or I HATE Scotchloks !)

[theoldwizard1]

This is NOT a Western Union splice. It had its day and it is gone.

As the title says I HATE Scotchloks. Sure they are quick but in a damp environment they will cause your wire to corrode and they just look nasty.

This how I handle splicing 12-20 AWG stranded wire, like you will typically find in a car/truck. The wires in these pictures are 14AWG automotive.

Let's start with the proper thing to cover your splices.

View media item 34799
Left to right, marine heat shrink, friction tape, Scotch 33+ and Scotch Linerless splicing tape. Not many years ago, friction tape was still widely used on most cars because it was cheap, gave a water resistant covering and it worked. You typically did not see it because it was used inside the harness which was covered "harness tape" (PVC tape with no adhesive). All work well, but I find the marine heat shrink the easiest to use and gives the nicest finish. Do NOT use the "buck a roll" stuff that you bought at HF. It will come apart.

Start by stripping off about 1" of insulation and installing about a 3" piece of heat shrink.
View media item 34800View media item 34801
Now twist together the bared ends. You need to get 1½-2 turns with each wire. You may need a bit more wire bared on each end for large diameter wire, a bit less for smaller diameter wire. Cover with marine heat shrink.
View media item 34803View media item 34804View media item 34805This type of splice will hold against a lot of force especially if marine heat shrink is used.


A very common thing to do is "tap" an existing wire. This hard to do because you typically don't have much slack. Cut your wire and bare about 1" on each end.
View media item 34807Take you new wire and strip about 4" off, but add 2" of heat shrink in the center of this area. Use 1 size lower heat shrink for this operation.
View media item 34808Twist on one end of the old (red) wire cooper with heat shrink (note larger size)
View media item 34809[/IMG]
Twist the other old (red) wire on the open end and cover with heat shrink.
View media item 34811
Another way to do the same using an uninsulated **** splice. Bare about 3/4" of the new and old wire. Twist together. Trim to the appropriate length to fit in a **** splice that is one size larger (14AWG wire, 10-12AWG **** splice)
View media item 34812CUT OFF the new wire (blue) at the splice (left hand side) and add heat shrink but don't shrink just yet. Repeat baring, twisting, triming and crimping with the new (blue) wire and and old (red) on the right hand side.
View media item 34813Apply heat shrink.
View media item 34814
None of these are anywhere near as quick as a Scotchlok. Tapping is ALWAYS more difficult because you never have enough room/spare wire to work.

 

[ptgb]

If your not going to solder it.. then this is the way to go, IMO


http://www.posi-lock.com/posilock.html

 

[awdblazer]

btw that tape is not 88!!!

 

[y20dth]

So you just twist it, without soldering it?
Is there magic involved?

 

[theoldwizard1]

btw that tape is not 88!!!

Yep ! Scotch 33+ Corrected in original post

 

[Harrison2]

if your going to twist them together and then heat shrink them you may aswell tin them with solder incase they are subject to load.

but I do also hate scotch locks and also bullet connectors, especially when people rewire a entire vehicle with them and house hold use cable.

 

[Highbeam]

Why not just use a **** connector plus heat shrink? I worry about the twist method loosening up and not being as significant a conductor as the rest of the wire.

 

[sdguy55]

Why not just use a **** connector plus heat shrink? I worry about the twist method loosening up and not being as significant a conductor as the rest of the wire.

It would be pretty hard for it to unwind considering its heatshrinked

 

[awdblazer]

honestly you should try 88 puts 33 to shame

 

[Sparkfarmer]

Please no one do this. Making an electrical connection with no type of crimp or solder should never be done. Scotch locks are **** I agree, but this is NOT the solution. Doing this is like changing your timing belt with nothing but a pair of Channellocks. It will work for a while but it is making a nasty mess unnecessarily. If you take any pride in your work always use a proper crimp connector or solder.

 

[theoldwizard1]

if your going to twist them together and then heat shrink them you may aswell tin them with solder incase they are subject to load.

I let you lay on your back under a vehicle/dashboard and try to solder.

 

[theoldwizard1]

Please no one do this. Making an electrical connection with no type of crimp or solder should never be done.

All US cars and trucks (and I suspect foreign vehicle) use harnesses that have no splice crimp connectors and they certainly don't use solder. In fact, last I knew, they were still using friction tape under the harness tape/convoluted tubing.

On very low voltage lines (crankshaft/camshaft position sensors which can be only a few millivolts) they will specify that there are no splices from connector to connector.

Personally, I prefer crimp splices, but good ones are hard to find (TE/Amp Solistrand) and most people will not have them on hand when they need them. (I have been building my selection of crimps for over 25 years.)


(30 plus years in automotive engineering)

 

[theoldwizard1]

Why not just use a **** connector plus heat shrink? I worry about the twist method loosening up and not being as significant a conductor as the rest of the wire.

It would be pretty hard for it to unwind considering its heatshrinked

Correct !

The marine heatshrink has special inside layer that melts at a lower temperature and bond to the splice and insulation. You have better hope you never need to get it off !

 

[kendogg]

So you just twist it, without soldering it?
Is there magic involved?

Ya, thats a REALLY bad idea. It may not pull apart easily, but it's not a mechanical connection at all. You leave open the possibility, depending on a number of factors - vibration, location, etc., of it coming loose, and a loose connection is going to arc, and even if it's a mm arc or smaller, it's an arc. Electrical arcs generate heat, and can cause fires. I'd rather see a scotchlock than those, personally. Especially under the dash. Both are equally bad under the hood, the scotch-lock less so if it's insulated air-tight. I either use standard **** connector crimps inside the car, or the uninsulated **** splices in pics 11 & 12. Thats how the harness on my LS swapped Volvo was built, and is about the closest thing we can get to a mil-spec connection without buying hundreds of dollars worth of crimping tools.


And FYI - nobody solders connections. Not a single mil-spec connection si soldered, crimp only.

 

[theoldwizard1]

Ya, thats a REALLY bad idea. It may not pull apart easily, but it's not a mechanical connection at all. You leave open the possibility, depending on a number of factors - vibration, location, etc., of it coming loose, and a loose connection is going to arc, and even if it's a mm arc or smaller, it's an arc.

I want to see an arc on a low voltage (as stated in the title) relatively low current twisted twisted connection.

 

[theoldwizard1]

If your not going to solder it.. then this is the way to go, IMO


http://www.posi-lock.com/posilock.html

Try to put 3 or 4 of those inside of a piece of existing convoluted tubing.

 

[Dick in Wisconsin]

Sooo ... I have a long wire inside the roof to side wall trim of my enclosed trailer for the top trailer lights. I want to put in more lights, like one more between the existing ones.

What is the best way to splice into that wire and create pigtails for the new lights? Scotch-Locks? Or is there a better way.

I've learned recently that best route to first class crimped ends is to invest is a very good crimper. Everyone agree?

 

[kendogg]

if your going to twist them together and then heat shrink them you may aswell tin them with solder incase they are subject to load.

but I do also hate scotch locks and also bullet connectors, especially when people rewire a entire vehicle with them and house hold use cable.

I somehow missed this. Solder can heat and make brittle small stranded wiring, as well as potentially damage the insulation. It can work, but you have to have very good control of the temp. It's also not as good of an electrical connection as a proper crimp. Hence, why as states, ALL military spec connections are crimped. Solder isn't as reliable.

 

[kendogg]

Sooo ... I have a long wire inside the roof to side wall trim of my enclosed trailer for the top trailer lights. I want to put in more lights, like one more between the existing ones.

What is the best way to splice into that wire and create pigtails for the new lights? Scotch-Locks? Or is there a better way.

I've learned recently that best route to first class crimped ends is to invest is a very good crimper. Everyone agree?

Agree on the good crimper. The 'ideal' way to do it, would be to fine where that wire starts and ends, disconnect it from one end, and pull it out (with a string or something so you can pull it back where it belongs). Measure, cut & splice in your pigtails into the wire, and pull it back thru the roof. Use the solderless crimp and marine heatshrink method, unless you have access to actual mil-spec crimps and crimpers. Even then, use the marine heatshrink, becuase it will seal the connections weather-tite. When finished, pull wire back with the string you attached at the end you disconnected, reconnect that end, and install your lights. Picture how Christmas lights are wired. All in series-parallel, so if one goes out, the rest still stay on.

 

[Dick in Wisconsin]

Agree on the good crimper. The 'ideal' way to do it, would be to fine where that wire starts and ends, disconnect it from one end, and pull it out (with a string or something so you can pull it back where it belongs). Measure, cut & splice in your pigtails into the wire, and pull it back thru the roof. Use the solderless crimp and marine heatshrink method, unless you have access to actual mil-spec crimps and crimpers. Even then, use the marine heatshrink, becuase it will seal the connections weather-tite. When finished, pull wire back with the string you attached at the end you disconnected, reconnect that end, and install your lights. Picture how Christmas lights are wired. All in series-parallel, so if one goes out, the rest still stay on.

Thanks Ken!

1. I can't pull the wire out; there are three lights on the wire now. I'd have to unfasten them. But its only three, maybe just start over?

2. What kind of a "thing" do I crimp onto the line to create the pigtail? I just don't see anything that is designed as a "tap" for close quarter other than the Scotch-Lock.

 

[kendogg]

Thanks Ken!

1. I can't pull the wire out; there are three lights on the wire now. I'd have to unfasten them. But its only three, maybe just start over?

2. What kind of a "thing" do I crimp onto the line to create the pigtail? I just don't see anything that is designed as a "tap" for close quarter other than the Scotch-Lock.

Hmm. It may be worth disconnecting and removing those lights, then rmemoving the wire, making your connections, then re-installing everything? Hard to say without pictures :/

 

[sdguy55]

If its really that tight I would honestly put in all new wiring. Wouldn't take that much longer and it would be easier

 

[Kevin C]

If you solder... You need to support the joint so no flexing occurs where the solder ends.

I prefer **** splices. The down side is the good tools are a bit pricey.

At work, I did test the OP's wrapped wire splice method. On a brand new splice, no measurable resistance (to .001 ohms). However the pull strength was less than four pounds. On a good crimp, I typically get at least 85% of the wires breaking strength ( 25 lbs or more). Solder gets you to 99%, but you lose flex at the ends of the joints.

Another concern is oxidation over time. There is no significant clamping force to prevent it where the wires contact each other.

Wizard, you have pitched this method a lot ( EDIT the twisted wire method), and I'm sure it works well enough. But the low mechanical strength and possible aging issues are big concerns. I thing there are a lot better ways to join wires (edit the crimp method you also showed).

BTW, the harnesses I have taken apart all had splices to join wires. Some used large crimps wrapped with tape, other used spot welded copper wrapped with tape.

 

[krivasgarage]

Anyone want to volunteer an explanation of the physics behind the statement that crimped conducts electricity better than soldered?

 

[theoldwizard1]

Sooo ... I have a long wire inside the roof to side wall trim of my enclosed trailer for the top trailer lights. I want to put in more lights, like one more between the existing ones.

What is the best way to splice into that wire and create pigtails for the new lights? Scotch-Locks? Or is there a better way.

I've learned recently that best route to first class crimped ends is to invest is a very good crimper. Everyone agree?

View media item 34813The new (blue) wire was spliced in with TE/Amp Solistrand **** splice

and these simple, cheap crimpers.

View media item 34367

 

[92GreenYJ]

Yeah I do as you described, except I ALWAYS solder every connection before I shrink it.

 

[theoldwizard1]

Anyone want to volunteer an explanation of the physics behind the statement that crimped conducts electricity better than soldered?

And that either conducts low voltage better than twisting 2 clean, bare ends together.

 

[Kevin C]

http://www.digikey.com/Web%20Export/Supplier%20Content/Tyco_8004/PDF/TycoAmp_Splice.pdf?redirected=1

Partial to PDIG series... The applicators are a bit pricey but can often can be found used for a fraction of the original cost.

 

[theoldwizard1]

I prefer **** splices. The down side is the good tools are a bit pricey.

I also prefer **** splices, but as previously stated, you don't need expensive crimpers.

Another concern is oxidation over time. There is no significant clamping force to prevent it where the wires contact each other.

Which is why I recommend marine heat shrink. Not truely waterproof, but highly water resistant. Of course so is friction tape.

Wizard, you have pitched this method a lot, and I'm sure it works well enough. But the low mechanical strength and possible aging issues are big concerns. I thing there are a lot better ways to join wires.

No argument with your pull test. Were you using narine heat shrink ?

BTW, the harnesses I have taken apart all had splices to join wires. Some used large crimps wrapped with tape, other used spot welded copper wrapped with tape.

I have NEVER seen that on a single wire splice. Maybe when 4-8 wires are spliced together.

 

[theoldwizard1]

http://www.digikey.com/Web%20Export/Supplier%20Content/Tyco_8004/PDF/TycoAmp_Splice.pdf?redirected=1

Partial to PDIG series... The applicators are a bit pricey.

Are you working on aircraft or what ! Solistrand is fine for typical automotive use.

 

[Kevin C]

Are you working on aircraft or what ! Solistrand is fine for typical automotive use.

Medical / Lab equipment. Once you try the ones I have been using its hard to go back.

 

[Kevin C]

I also prefer **** splices, but as previously stated, you don't need expensive crimpers.


Which is why I recommend marine heat shrink. Not truely waterproof, but highly water resistant. Of course so is friction tape.


No argument with your pull test. Were you using narine heat shrink ?


I have NEVER seen that on a single wire splice. Maybe when 4-8 wires are spliced together.

I have had several harnesses with three wires spliced that had a welded connection.

I used adhesive shrink... the wires unwound and the shrink broke in the middle.

Corrosion resistant mechanical connections requires high unit pressure to insure a connection that will last. Not seeing that with twisted wires.

http://www.molex.com/pdm_docs/ats/TM-640160065.pdf

The Bible of crimping.... Page 24 is pretty interesting, in particular the pull strength table.

 

[Georege301]

Good connectors? I am all for crimp connectors, mainly because I can't solder for s**t (!) But, can someone give me a brand name or a source on line for some good connectors? What I have been getting is very hit and miss.

thanks
george

 

[theoldwizard1]

Good connectors? I am all for crimp connectors, mainly because I can't solder for s**t (!) But, can someone give me a brand name or a source on line for some good connectors? What I have been getting is very hit and miss.

I prefer uninsulated (so I can put marine heat shrink over them. A much "cleaner" look, IMHO.

TE/Amp Solistrand Let me Google that for you !

Most electronic supply houses. (Digikey, Mouser, Jameco, Newark, Allied, RS, etc)

 

[JeepinMike]

Good connectors? I am all for crimp connectors, mainly because I can't solder for s**t (!) But, can someone give me a brand name or a source on line for some good connectors? What I have been getting is very hit and miss.

thanks
george

They have heat shrink & crimp, heat shrink & solder, and head shrink&solder&crimp.

http://www.waytekwire.com/item/32970/****-CONNECTOR-SEALED-CRIMPED/
http://www.delcity.net/store/Heat-Shrink-****-Connectors/p_801794

-mike

 

[92GreenYJ]

I prefer uninsulated (so I can put marine heat shrink over them. A much "cleaner" look, IMHO.

TE/Amp Solistrand Let me Google that for you !

Most electronic supply houses. (Digikey, Mouser, Jameco, Newark, Allied, RS, etc)

Same here. But when I have to use a connector I crimp it, solder it, then heat shrink it. Yeah, I go thru a LOT of solder

 

[lbperry]

Same here. But when I have to use a connector I crimp it, solder it, then heat shrink it. Yeah, I go thru a LOT of solder

I use **** connectors without the wire stop in the middle so I can intertwine the wires. Then I crimp, solder, and heat shrink.
And yeah, I wear a belt and suspenders too.
Good Luck,

 

[RedBKM]

+14 for solder whenever possible. I buy only uninsulated rings, spades, **** splices etc. and solder them all. Marine shrink afterwards for good measure.

Ever found one of those hollow tubes full of green dust where copper used to be? Wire will wick moisture up its entire length if given enough time. The solder will seal the terminal and the marine shrink closes the opening at the back.

 

[66dave]

To the OP, why do you say the wester union (line mans splice) has had it's day? I am glad to see a brief write up this. Even if you know what you are doing it is good to see another persons opinion.

Others have asked about soldering, soldering is great as long as you know what you are doing. Many people end up with cold solder joints or just to much solder (or maybe not enough). This often happens when you are in uncomfortable situations like soldering upside down under the dash (unfortunatly i admit I have done this in the past). These situations could lead to higher resistance which could cause signal degregation or heat.

Crimping properly will actually cold weld the materials together. That brings up another point that you need to use the proper matierals. If dissimilar metals are used you can have galvanic effects (this may take a long period of time) or if using improper crimping tools the joint will be inferior. This inferior joint could exhibit the same issues as described in the poor solder joint section.

In the end as long as you do the job correctly either are very acceptable.

FYI-in the semiconductor industry they do not allow cables to be soldered, low or high voltage. On occation there are unique RF cables that require the center electrode (anode pin) to be soldered.

 

[kamesama980]

Oldwizard: for splices my old toyotas (late 80s/early 90s) have uninsulated crimps taped individually and with the harness under the corrugated tube, then more tape (non-sticky harness tape usually). I've seen soldered connections too but not 100% sure those are OE.

I'm in the solder camp. If it's underneath the console, take more parts off to get it where you can solder it, even awkwardly. I've dealth with a few bad splice jobs and that's enough to make me do them thoroughly.