Wired Tight

Published on January th, 2009

We seem to have an unquenchable thirst for the latest and greatest hard parts in our 4wd industry. We all want that set of killer axles, transfer case, engine, tires or newest widget that will make our rig ‘bombproof’ on the trail while with our buddies. We don’t want to be the one everyone waits on while we fix our junk on the trail, right?

On a recent outing, we had a nice buggy break down in a pretty rough spot. As we worked on the rig, we had come to the conclusion it was an ignition issue (no-spark condition). As we sorted through and began to pull dash panels out, there was a mess of wires within this spliced MPI harness that would have made Thomas Edison himself cringe at the very sight before him. Here we are trying to chase down a problem, which was massively further complicated by the lack of planning on the harness installation. In the owner’s defense, I have seen a lot of vehicles that suffered from the very same issues. We seem to skip by a lot of the basics on the road of desire to having the latest ‘ultra bling’ part. We did get the problem fixed, but we were lucky with the availability of parts and man power.

Modern fuel injected engines are a wonderful thing, but they can be very stubborn if something is not in order. When your dad’s 1963 Chevy refused to start, you only had to deal with a couple of possible causes. If your recently swapped Hemi® or LS1 engine doesn’t fire, you could have over a hundred possible causes that caused a no-start. You can avoid a lot of headache and frustration by paying attention to the quality of the job you do on your wiring before it leaves your garage. We are going to discuss some of the basic techniques and materials required to wire your vehicle cleanly and reliably.

The first thing is having the correct tools to do the job at hand. Now, as with anything, the deeper into this area that you go the more specialized (and expensive!) the tools become.

Basic Kit:

  • Digital Multi-Meter: The ability to measure voltage, resistance, continuity and current. If you are looking at options, the availability to measure frequency and pulse width is also a plus.
  • Test Light: To find ‘hot’ leads quickly.
  • Wire Strippers: Get a decent set.
  • 40 Watt Pencil Soldering Iron: Try to get one with ground prong. Get a stand with it along with a sponge pad for cleaning the tip.
  • Electronic Solder: 60% Tin and 40% Lead with a Rosin based Flux or the new version that is Lead free 97% tin, 2.5% silver and 0.5% copper with Rosin based Flux.
  • Solder Wick: Copper braid that will remove excess solder if necessary.
  • Terminal Crimper: You may need a few different ones depending on terminals.
  • Wire Terminal Tool: Removes terminal pins from connectors.
  • Heat Gun: Very handy to have for the heat shrink tubing.

Basic Soldering Techniques:

  1. ‘Tin’ the soldering iron: This is done by preheating the soldering iron and applying a few drops of solder. Then, wipe the tip on the damp sponge pad to clean it. You can then apply another bit of solder on the tip to help with heat transfer onto the wire.
  2. Strip and prepare the lead to be ‘tinned’: Make sure the harness is clean of grease and oil before working on it. It is very easy to contaminate a solder joint.

Strip the required material length (usually .5” to .75”) and put a slight twist into the strands to keep them in place.

  1. ‘Tin’ the leads: Place the tip of the soldering iron at the end of the lead to be tinned. Place solder above the iron but on the opposite side of the lead. Solder will proceed to ‘wick’ or follow the flow of heat down the joint. Do not force the flow of solder by moving the tip of the iron down the lead closer to the insulation to quickly. When the solder reaches the insulation or slightly under it, you are finished. Some of the joint types will be easier to assemble if one the leads are left ‘un-tinned’,
  2. Identifying a Correctly Soldered Connection: You are looking for a good flow of solder when it is applied. The finished joint will be shiny or silvery in appearance. If you disturb the parts while you are soldering, there is a good chance you will have created a ‘cold’ joint. These will appear as dull gray joints and are prone to failure. Redo the joint as necessary to ensure correct adhesion of the solder. Make sure you try to solder ‘in-position’ as much as possible. This greatly aides in creating good, strong joints.
  3. Joint Type Decision: Now you will have to decide what type of joint will work for what you need to do. There are quite a few types of joints, but I am going to cover what I think is most relevant in wiring an automotive project. Remember to place a piece of the proper size heat shrink tubing on the lead before you solder the joint together!

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        • Lap Splice: For joining two conductors in a straight line. This joint is non-structural joint and can be prone to failure if not properly done.
        • Western-Union Splice: For joining two conductors in a straight line. This joint is a structural joint and is very strong and resistant to vibration induced failure.
        • T-Tap Splice: For joining a conductor into an existing wiring loom (inline). Depending on the size of the wire, one or more conductors can be done that way. This is also a structural joint and very strong.
        • Lash Splice: For joining one or more conductors into an existing loom (inline) or as an end branch. This takes some time to do depending on size of wire but is also strong.

Not everything you connect on your rig will need to be soldered. Sometimes it is necessary for you to have different terminal ends, connectors, plugs etc. I want to go over some options that are available. Most everyone reading this will have the $ 9.99 kit from some auto part store or flea market with butt, fork, blades etc in their garage. Most of all the components included in those kits are garbage or sub standard. The one thing that can be said about terminals is you get what you pay for, period.

  • Single Connector Types: Ring Mount, Fork, Blade, Spade, Bullet, Butt, Push-On, Flag, Pin, Tap and other more specialized connectors. All of these versions can come insulated or non insulated
  • Single Connector Type Construction: The problem with most of the part store or flea market kits is they are constructed from cheaper materials and are not designed for performance applications. Performance meaning extreme vibration, heat, stress, and harsh weather conditions. The good news is there are products that fit our needs perfectly.

1. Least Desirable Type: ‘Generic’ terminal kits. They use PVC insulation which is less desirable then Nylon Insulation. No idea on terminal material, type of plating, heat resistance, or capacity. They will be a crimp-on only which leaves the terminal open to corrosion and fatigue, thus causing possible intermittent electrical problems. Read: Headaches!

2. More Desirable Type: Name brand manufacturers like AMP, Thomas&Betts, 3M and Wurth to name a few. These will have Nylon insulation which resists heat and vibration better than the Vinyl versions. The terminal will be Copper with bright Tin plating for conductivity and corrosion resistance. The terminal material construction will be properly sized for its intended voltage use and will not deform as easily when mounted. The inner barrels of the terminal will most likely be brazed or have a Brass reinforcement sleeve.

3. Most Desirable Type: Name brand manufacturers like AMP, Thomas&Betts, 3M and Wurth to name a few. They will have heat shrinkable Nylon outer insulating bands. They will have solder pellets inserted into the brazed barrels and possibly lined with heat-activated adhesive. These connectors will be crimped first, and then heated which will melt the pellet and solder the joint. The outer shrink tube will shrink, thus sealing and securing the connector all at the same time. This will provide you with a soldered connection that is sealed to corrosion and very resistant to vibration.

A few tips for crimping connectors:

  1. A good set of crimpers will have provisions for both insulated and non-insulated type terminals; make sure you are using the correct slot and size.
  2. There is a proper way to crimp terminals and that is with the indent from the crimping tool opposite the barrel seam on the connector.
  3. Do not over do it on the crimp as you will crush the wire strands and this can cause failure of the wire in the connector.
  4. Place heat-shrink tubing over the connector for added strength and sealing. The same applies to heat shrink tubing as the connectors; the better stuff is made from Polyolefin while the cheaper stuff is PVC.

To locate the good terminal ends you may have to do some looking around. They are all available from companies on the internet if you are not able to locate any locally at specialized supply houses.

We seem to install a lot of widgets to our rigs. Our 4wd’s are not the same as someone’s street rod project which when it is done, it’s more than likely never to be touched again. We are always changing, adding something, or taking something off of our vehicles. How about for things that need to be removed or replaced more frequently or are more complicated than one or two leads? This requires some sort of harness and or plug connector. There are quite a few manufacturers of different harness connectors if you look around. In my opinion the ‘Weather-Pack’ and ‘Metri-Pack’ connectors that were developed by Delphi/Packard Electric are perfect for us and reasonably priced. Most of you will be familiar with them already with their use in modern automotive harnesses and probably already have them on your rig if you are running any sort of late model GM engine. These are an environmentally sealed connection systems developed to withstand exposure to extreme temperatures, moisture, and harsh engine compartment fluids and chemicals with unfaltering performance. They consist of mating heat stabilized polyamide housings (known as “towers and shrouds”) with male and female “pin and socket” terminals. These work in conjunction with self-lubricating silicone ‘Pack’ connector seals, cable seals and cavity plugs for the various applications. Basically, you can put together what you need from kits.

Weather-Pack Specifications:

  • They are designed to carry .05 to 16 VDC with a maximum of 20 Amps.
  • They are available in one to a total of six wire configurations.
  • They will accept 22 gauge to 12 gauge wire with matching seals.
  • They have ‘indexing slots’ so they are re-installed the same every time.
  • They can be assembled without the use of a special crimping tool if you are careful, but the tool does make it a lot easier and a 100% positive connection.

Metri-Pack Specifications:

  • They are mostly used on switches, sensors and devices.
  • There are a few versions that have mates (both male and female connectors).
  • They are designed to carry .05 to 16 VDC with a load range of 14 to 46 Amps depending on the size of the connector.
  • There are a lot of “application specific” components in this series. Housing variations within a given series are common and most similar looking parts are not interchangeable. This does not mean they can not be rewired, but if you have broken that TPS or IAC plug on your harness, off to the junkyard you go to get another one to replace the broken one.
  • The specifications on these are very similar to the ‘Weather-Pack’ versions.

Weather-Pack Connector Installation:

The first thing is to decide how many leads are involved in the pigtail that you need to build. The connectors will only handle up to six leads per connector so that is the limiting factor. Once that is figured out, choose the correct size terminals and seals for the style connector you are going to use. Remember the ‘tower’ or male style connector will use the female style metal terminals. The ‘shroud’ or outer connector will use the male (solid) style terminals. Before you strip the leads, slide the seals onto the leads in the proper orientation. The smaller outside diameter of the seal will face the terminal. Proceed to strip all the leads to the required length. Place the terminal with the seal in the crimping tool and proceed to crimp the end on. If you are using a factory tool, it will provide the correct amount of crimp so all you have to do is squeeze it. If you are improvising, be careful not to over crimp and deform the terminal end so that it does not seat into the connector body correctly! Once this is done, all that is left is to insert the terminals into their respective bores in the connector body. Push them in until you feel the ‘click’ of the terminal tang. Once that is complete you can fold the back of the connector body down and snap it into place. This insures a tight seal.

More Harness Plug Options:

There are all sorts of connectors both new and used that can be adapted for the wiring job on your rig. If you are starting completely from scratch with a buggy, your options are of course broader than if you are using an existing vehicle. There are connectors called ‘cannon plugs’ that are sourced from aircraft that work great for modular harnesses. Some of them will accept large amounts of conductors. These are perfect to use through your firewall since they are waterproof, vibration resistant and interlocking. They do require a few more specialized tools to work with, but they are totally ‘trick’ when installed. If you spend some time on the internet requesting catalogs from electrical suppliers, you will see there are a multitude of options available to construct your harness and wire your rig. The goal is to plan the job and pay attention to details. This will ensure a job well done.

The quality of the wiring work performed on your rig, most likely will not win you any praises from your buddies. Only you will appreciate that it was done correctly the first time. At least you will have the satisfaction knowing you won’t be ‘that guy’ that holds everyone else up on the trail while they try and sort through your ‘rat’s nest’ that you call a harness.

Comments

  1. Posted by teatr uliczny on April 3rd, 2010, 03:47

    This is such a great resource that you are providing and you give it away for free. I love seeing websites that understand the value of providing a quality resource for free. It?s the old what goes around comes around routine.

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