We will look at how to fix wiring harnesses in this article. Wiring harness components like connectors and wires can melt, burn out, become brittle, or wear naturally over time.
This situation requires immediate fixing because it can make sensors or other parts misbehave if the exposed copper wire arcs out.
Fixing these issues is not a complex process, though. So let’s look at the automotive wire harness repair process below. Read on to learn more!
Table of Contents
- Wiring Harness Components
- How To Fix Wiring Harnesses
- Things To Keep in Mind When Fixing Wiring Harnesses
- How To Fix Wiring Harness: Put Safety First
- How To Fix Wiring Harness: Understand the Circuit
- How To Fix Wiring Harness: Use the Correct Wire Gauge
- Break Wires Carefully Out of the Harnesses
- How To Fix Wiring Harness: Avoid Using Solid Core Wires
- How To Fix Wiring Harness: Use the Correct Connector Size
- Ensure Connectors and Backshells Are in Good Condition
- Secure the Wires Using Heat Shrink Tubing
- Avoid Using Quick Connector Kits
- Avoid Using Electrical Tape for Insulation
- Wrap Up
Wiring Harness Components
Automobile wire harnesses contain these parts.
- Individual wires
- Electrical connectors
- Backshells
- Splices
- Shrink tubing
- Contacts
- Terminals
- String tie/braid
Replacing this complete electrical connection is uncommon because repairs (replacing the damaged sections) are cheaper.
But it might be necessary if you can’t find the fault or the complete wiring harness catches fire.
Also, replacing the entire cable harness might be more economical if more than three or four parts show signs of failure.
The same case applies to damaged injection molded wiring harnesses. Replacing the entire unit with a new one is cheaper than doing repairs.
A car wiring system undergoing repairs
And we recommend replacing the complete harness for sensitive electrical components (like airbags) or harnesses that are difficult to locate.
Other than that, you can fix the harness using the steps below.
How To Fix Wiring Harnesses
Fixing a wiring harness involves replacing the damaged section.
For instance, if you find a short circuit in a connector or a ground fault (exposed wire), fit in a new connector or wire.
Required Tools
- Crimping tool
- Heat gun or lighter
- Electrical tape (black tape) or automotive harness tape
- Wire cutter
- A single-edge razor blade, knife, or pair of scissors
- Wire stripper
A wire stripper cutter tool
Disconnect the battery before beginning the repair process to prevent short-circuiting and ground faults.
Step 1: Access the Damaged Section
Wiring harnesses usually have electrical tape or corrugated tubes to wrap the individual electrical wires.
Once you’ve identified the bad wire or connection point, cut the encasing tape or tube using the single-edge razor blade to access the cables.
A chewed wire harness corrugated tube
Pull the wires out of the tube and inspect them visually for issues like burning, melting, breaking, etc.
Also, check the connector for corrosion. Severe corrosion warrants a replacement. But if not extensive, clean the component thoroughly.
Step 2: Confirm the Wire Harness Connectors and Wire Gauge are the Same
If replacing the wire harness plug connector (or socket), confirm the new and old pieces are the same. Also, check the wire gauge from the connector, if it has a wire attached.
And wiring color codes can be slightly different if the electrical connector is not an OEM product.
To avoid mistakes, cut one wire shorter to indicate its polarity. And do the same on the wire side.
A wire harness with multicolored cables
If replacing wires, flex them first to check if they are brittle and the extent of the brittleness. It is advisable to replace brittle cables to avoid electrical issues in the future.
Once you’ve determined the length of wire to cut, check the broken wire insulation color and size (gauge).
Get wires that match these properties, then proceed to the next step.
Step 3: Strip the Wire Ends
Cut the bad or corroded wires, then strip the remaining portion to about the length of the razor blade.
Also, strip the replacement wire, and use the correct wire gauge size slot on the wire stripper to remove the insulation.
Step 4: Connect the Wire Ends
Twist the wire ends together to prepare them for crimping, then insert them into insulated weatherproof connectors while ensuring the exposed wire is inside the insulation.
We recommend using insulated butt connectors for this electrical connection.
Solder seal insulated butt connectors
Crimp the connector after inserting the wires, then tug the cables to check the connection’s mechanical strength.
The connector should not loosen as you pull the wires. If everything looks good, go to step five.
You can solder the connections instead of using connectors in some cases.
Solder is sturdier and more vibration resistant than connectors because it involves melting metal to join metal. But make the connection hot enough to link the wires.
And place a heat shrink tubing around the solder joint.
Step 5: Melt the Insulation
Butt connectors usually have heat shrink tubing for insulation. Use a heat gun to melt the protective cover over the crimped joint to keep out water and provide corrosion protection.
If using a lighter, sway the flame back and forth to avoid burning the material.
A heat gun shrinking a heat shrink tubing
Step 6: Wrap the Wires
Wrap the wires using electrical tape to bundle them together. If they were in a corrugated tube, insert them into the cut section, then wrap the area using black tape for coverage.
But don’t wrap the wires near the connector because you can apply unnecessary pressure and loosen the link.
An electrician applying electrical tape on an electrical cable
Step 7: Testing
Reconnect the battery and turn on the vehicle. Test the component to determine if the connection functions as required.
Things To Keep in Mind When Fixing Wiring Harnesses
Keep these factors in mind before attempting repairs on these complex wiring harnesses.
How To Fix Wiring Harness: Put Safety First
Although the car operating voltage is relatively low compared to the AC we use in our houses, it is still dangerous.
Always turn off the vehicle and disconnect the battery before cutting or touching the cables. They might have unnoticeable damaged insulations, so be cautious.
But you need the battery connected if diagnosing the wires using tools like multimeters to test the voltage level. So get the proper tools for this task, such as high-voltage insulating gloves.
How To Fix Wiring Harness: Understand the Circuit
Modern vehicles have complex electrical circuits that get affected by factors like resistance. So don’t splice them too long when replacing cables or connectors.
Also, avoid over-soldering the joints. You can increase the resistance along the line, which can tamper with the low-voltage signal quality, resulting in computer miscalculations due to signal errors.
How To Fix Wiring Harness: Use the Correct Wire Gauge
Wire gauge is a significant factor when working on electrical wiring systems. Thin wires increase resistance, which hampers electrical current flow.
And if increasing the wire length from the power source to the destination, use a thicker wire to minimize the voltage drop.
A wire stripper with different wire gauge levels
The best practice is to use the same wire gauge and length as the section you are replacing to avoid resistance and electric current issues.
Also, use the correct wire color to ensure future repairs are accurate.
Break Wires Carefully Out of the Harnesses
If repairing an individual wire in a harness, pull it out gently to avoid damaging the connector or saddle.
Also, avoid bending the cables near the connectors to prevent cuts or disconnections.
How To Fix Wiring Harness: Avoid Using Solid Core Wires
Solid core wires can break when exposed to continuous shock and vibration. The cuts can create arcing points that lead to discontinuity.
So the cable will work initially, but you’ll get issues later.
How To Fix Wiring Harness: Use the Correct Connector Size
When using crimp-style connectors, pick the right size that matches the wire gauge. If too large, you won’t have a solid crimp.
And if too small, the wire won’t fit. You’ll have to remove or cut some wire strands, which weakens the circuit.
Ensure Connectors and Backshells Are in Good Condition
Check and replace hoods/backshells and connectors if severely corroded before repairing the wires.
Secure the Wires Using Heat Shrink Tubing
Always use heat shrink tubing to wrap the wires after joining them. Butt connectors come with these insulators, but if you solder the joint, use an external tube to protect it.
These tubes usually have an adhesive lining or premeasured solder that softens and takes the joint’s shape to provide insulation from moisture, dirt, contaminants, elements, etc.
Heat shrink tubing applied over the wires
And the tube should be slightly larger to ensure it slips over the wires and wraps around them firmly after heating.
You can use insulation tape as the secondary seal.
If replacing or repairing several wires, wrap the tubing around the individual wires, then insert the strands in a larger tube to make the wiring neat.
Avoid Using Quick Connector Kits
Although convenient, quick connector kits cannot connect wires tightly and can snap due to car vibrations.
Avoid Using Electrical Tape for Insulation
Black tape is handy for house wiring but can fail in cars because of exposure to the elements and temperature variations.
These conditions will loosen the tape and expose the wires. So you can only use this tape to bundle the cables or as secondary seals.
But don’t replace heat shrink tubing with insulation tape.
Wrap Up
Fixing wiring harnesses is relatively easy compared to other car repair tasks. You can call an electrician to help you, but doing it yourself can save some money.
That’s it for this article. Let us know in the comments below if you encounter any issues doing these repairs.
