Grassroots Motorsports

Register Log in to GRM
- Community

Birthdays
Recently on the Classic Motorsports forums

Subscribe get a full year for only $23.95 Sample Free Test Drive—no strings attached

Login to post Forums » Grassroots Motorsports » Under hood wire splicing

Aug. 4, 2008 7:51 p.m. fastEddie Dork

The previous owner of my Max didn't have a frackin' clue when it came to wiring and has made some really odd/stupid/weird wiring cuts and splices. Two words - speaker wire and scotch tape! OK, so that's more than two words....

Anyway, the car somehow runs pretty good so I'm not messing with it for the moment (wish I had dug a little deeper before signing on the line - live and learn!) but this winter I plan on tackling the issues one by one. So what is the proper method for splicing and repairing. I'm assuming solder or using pre-made butt or splice connectors. What about sealing? Can I use normal heat shrink tubing? Will it hold up under hood? Anything else to look out for or do?
Aug. 4, 2008 7:58 p.m. mad_machine SuperDork

can always use heat shrinkable tubing after you solder the wires together.. just make sure you put the tube over the wire and slide it out of the way before you solder.. I think everyone makes that mistake at least once.
Aug. 5, 2008 3:03 p.m. dculberson New Reader

They sell heat shrink with an adhesive liner built in. That would give you the best seal. I've bought it in bundles on eBay. Search for "heat shrink adhesive"

For example:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=320281900938

(Disclaimer: never bought from those folks, no idea if their product is good, etc.)
Aug. 5, 2008 3:25 p.m. Dr. Hess UberDork

I prefer solder and heat shrink myself. There is quite a debate always with the crimp people, but I maintain that unless you have the proper crimping equipment and supplies for your exact wire size, you will be better off soldering and heat shrinking. Of course, rosin core solder only.
Aug. 5, 2008 3:27 p.m. dan_efi New Reader

put a little bit of paste flux on the wires and use the iron to heat them up until it melts throughout the wires/joint and sizzles. Then solder. Makes life happy.
Aug. 5, 2008 3:44 p.m. 16vCorey Dork

mad_machine wrote:

can always use heat shrinkable tubing after you solder the wires together.. just make sure you put the tube over the wire and slide it out of the way before you solder.. I think everyone makes that mistake at least once.

That's my method too, and yes, I've made that mistake at least once.
Aug. 5, 2008 7:41 p.m. dculberson New Reader

(I of course meant to combine the adhesive-lined heat shrink with soldering the connection... just in case you didn't pick up on that.) :-)
Aug. 5, 2008 8:21 p.m. stuart in mn Dork

Try to make the soldered splice in a spot where the wire won't flex or be subject to stress or vibration - the solder joint will be hard and stiff, so wire on each side of the joint can fatigue and crack. You can get colored shrink tube as well, which may help disguise the repair if you can match the color of the wire.

If there are a number of wires bundled together with what looks like electrical tape, don't use regular old adhesive tape as the heat under the hood will eventually make it into a sticky mess. Eastwood company sells a non-adhesive wire harness tape that works pretty well - it's real stretchy, so you just wrap the wires together tightly with it then tie off the end.
Aug. 5, 2008 9:46 p.m. dean1484 HalfDork

Solder and shrink wrap is the best option... . .

BUT... . . Wire repair 101 with out soldering iron in the middle of no ware has necessitated the use of butt connectors. After installing and crimping the connection in place I then put a dab of high temp silicon (rtv orange or copper) around where the wires go into the but connector. A word of warning. Do all the crimping you are going to do first and then install the RTV. If you don't you will end up with the stuff all over the place. If you get good with the RTV you can put the end of the RTV tube on the end of the but connector and it will force it in to the connector and around the wire leaving a neat finished appearance.

I Have done this more times than I care to admit and no issues. Obviously the RTV is to seal the splice from water/moisture preventing corrosion. It also seems to add support and bond the wires insulation to the connector.

Another way I have done it was to dip the wire in dielectric grease and then put them in the connector and crimp. You then smooth off the greens at the ends making a nice neet water proof seal around the wire where it goes in to the conector. This seemed to work well. Several years later I looked at an installation done this way and the grease was still in there. I would not do this in high temp areas like around the motor. I am not sure what the melting point of dielectric grease is.
Aug. 5, 2008 10:03 p.m. oldopelguy HalfDork

Buy the butt-splices without insulation on them and then heat shrink over them. Get the silver plated ones if you can (MIL-spec) since silver oxide conducts nearly as well as silver. The OD of the non-insulated splice should be close to the OD of the insulation on the wire, so you get a nice clean looking connection that seals up really well.

A properly butt-spliced connection is every bit as good as a solder connection and a lot less difficult to do right. The trick is to get a real crimper, the kind with a ratchet action so it has to go all the way closed before you can open it again. That kind ensures you use enough pressure on the splice to properly pressure weld the connection. If you spent under $30 on it, it's probably not a great crimper.

Solder is good too, I just don't like the way the lead oxidizes in an automotive environment for the long-term. There's also a lot of idiots who use plumbing solder or plumbing solder flux when they try to solder wiring and the acid in the flux does terrible things to the wires in short order.
Aug. 6, 2008 7:16 a.m. fastEddie Dork

oldopeldude, I like your idea. Any online sources for these uninsulated splices?
Aug. 6, 2008 7:47 a.m. oldopelguy HalfDork

Del City would be my first choice, pretty reasonable pricing and quality components. They also sell a decent low-end ratcheting crimper for right @$30 that'll do most things a normal guy wants to do and last a long time.

They also have lugs that already have adhesive lined heat shrink on them instead of plastic insulation. I've never done a cost analysis on them because I have miles of heat shrink in the shop already, but they sure would be convenient and you wouldn't forget to put the heat-shrink on before you crimp.
Aug. 6, 2008 10:39 a.m. SoloSonett New Reader

dean1484 wrote:

Solder and shrink wrap is the best option... . .

BUT... . . Wire repair 101 with out soldering iron in the middle of no ware has necessitated the use of butt connectors. ....

This works well when you back your Sonett off the trailer and the dash goes up in smoke! Luckliy there was a Wally Market across the street!

Ran all day with a new ignition lead!
Aug. 6, 2008 10:45 a.m. jikelly New Reader

I rewired my stang 4 years ago now with the butt connectors. I used no insulation after crimping the wires. I keep wondering if I'm going to regret not soldering the connections. So far everything's still peachy.
Aug. 6, 2008 11:38 a.m. wlkelley3 Reader

Matter of opinion. I prefer to use butt connectors with heat shrink over the splice primarily because of my aviation background. I have soldered wires and covered with heat shrink. Both methods work if done right. If doing more than one splice in a bundle, don't put the butt splices next to each other, stagger them. This will reduce the chance of chaffing issues. And what the taught us in aviation.
Aug. 6, 2008 12:06 p.m. Dan G Dork

This is a page describing a good way to do a soldered butt splice...

Solder Lap Splices

Its from this page for DIY airplane wiring tips, very good resource...

DIY Articles
Nov. 12, 2009 2:31 a.m. AdamDecker

SunTouch Warm Floor wire heat cable is an economical solution for an electric radiant heated floor to warm tile in small or large areas. Warm Wire lets you customize a layout around curves, angles or objects and choose 10, 12 or 15 Watts per SF of heat
Nov. 12, 2009 5:06 a.m. BoxheadTim Reader

Does that Warm Floor E36 M3 heat canoes then, too?
Nov. 12, 2009 7:29 a.m. HappyAndy Reader

fastEddie wrote:

oldopeldude, I like your idea. Any online sources for these uninsulated splices?

radio shack has un insulated but connectors, IDK about the mil spec though, also they have but connectors with adheasive shrink wrap covers, I use those alot and they are great. If the repair is an area that doesnt flex much solder is best, but if the wire is subject to movement but connectors may be better. I have made a few wire harnesses from scratch for industrial vehicles and I use splicing tape to wrap the harness when its all put together; that is the type of tape mentioned by some one else that doesn't have much adheasive, but you strech it out as you wrap and it bonds to itself, it is available at electrical supply stores, I buy mine from grainger. The eastwood stuff is more expencive, but possibly is made for higher temps.

You'll need to log in to post.