What A Tangled Web We Weave, Tony Passwater, BodyShop Business, February 1998

Now that all the metal repair and refinishing has been completed, it's time to start thinking about reinstalling all the electrical components and wiring removed before and during the repairs … right? Wrong!

"Rewiring the vehicle after the repairs" actually must start at the beginning of the process - not at the end. During disassembly of the vehicle (staging) for the initial inspection or reinspection, careful planning and procedures must be in place to ensure reassembly can be done properly and efficiently after the metal and paint work are completed.

There are five basic areas of this process to look at: disassembly, protection procedures, reassembly, repairs and verification. Following proper procedures for all five of these will improve efficiency and the quality of repairs during the rewiring process.

Disassembly Procedures
The disassembly process can begin during the initial inspection of the vehicle when writing the estimate. Removing components without properly documenting their location, mounting configuration or connections can lead to many hours of wasted time - not to mention possible damage to the systems involved.

To start this process:

• Begin by taking pictures of complex electrical systems with a digital or video camera. Video cameras can really be a big help because they can also include audio explanations to assist in the reassembly later.

Since the battery may also be disconnected, it's important to document electronic memory items that may be lost when the power has been disconnected, such as the customer's radio station presets. These should be written down and kept with the vehicle's file and on the repair order in the vehicle.

It's also important to note that disconnecting the battery may require a specific procedure for many vehicles. If a service manual isn't available, look in the owner's manual for warnings and procedures.

• When disconnecting any electrical component, be careful. Electronic component connections are intended to disconnect easily if the correct release is found. Pulling directly on the wiring to "give it a little help" isn't the best solution to a difficult release clip.

If it's necessary to remove the wiring terminal from the connector or connector block so the wiring can pass through an opening, it will generally require special tools. These tools allow for proper release without damaging the wire terminal or connection block.

• When connections are disconnected, label the component to the connection. This can be done many ways. For instance, commercial marking tapes are available, which allow for easy positive identification during reassembly. Colored tape can also assist in matching components and connections for proper assembly. And, again, a video camera can be a great assistant.

Wiring diagrams also can be very helpful to identify reconnection locations for connection blocks when the wiring is removed or torn from the connection. But, keep in mind that the wire color entering a connection block doesn't always match the wire colors of the other connector. In a case like this, a wiring diagram is very helpful.

• Place each component and its mounting hardware together in a parts bag, box or container. Mark each bag with the same color or number used for its vehicle connection.

Also, keep components separate - and organized. This will improve reassembly dramatically.

• Place all removed components in a parts cart in order of removal.

Protection During Repairs
Once electronic components are removed from the vehicle, it's very important to protect them from damage until they're reinstalled. This not only includes protection from physical damage, but also from excessive heat and electromagnetic interference (EMI).

If the component is completely removed, placing it in a parts bag or box and storing it in a parts cart normally will be fine - as long as the parts cart isn't stored too close to a power source producing excessive EMI. Typically, auto collision facilities wouldn't have this problem, but high-frequency equipment, such as a heli-arc welding machine, can produce a detrimental EMI to sensitive computer equipment.

The more common situation that requires additional precautions is when the component isn't removed completely from the vehicle but repositioned during the repairs. This includes wiring harnesses and sensors.

If any component is just repositioned, it's important to:

1. Place the component(s) away from possible damage during the repairs. During structural work, hammering, cutting, heating and welding can damage electrical wiring and electrical components. It's important to ensure this doesn't happen.
2. Don't allow components to "hang" from their connectors.
3. Don't coil or lay the wiring harness in an area close to welding or near the welding unit. Induced voltage - the ability of a power source to cause current flow in another circuit without actual contact - can occur from this condition and can damage or activate electronic systems.
4. Protect wiring connectors from body and paint dust. Many of the connections used today include a die-electric grease to provide a seal from moisture. This grease will attract dust when exposed during disconnection, so it's advisable to cover these connections with plastic bags to prevent contamination.
5. Since static electricity can also damage electronic systems, don't touch these components without being properly discharged (grounded). Also, don't touch the terminals of connectors directly unless grounded and wearing rubber gloves. Static charges and acid from fingers can damage the component, and acid can cause corrosion to form.

Commercial devices are available to ground yourself during handling of sensitive electronic components.

Reassembly
To reinstall electrical components, reverse the disassembly process to ensure proper location and wire routing. Again, documenting the disassembly allows for much easier reinstallation since reassembly may take place weeks after the disassembly.

During reassembly, follow these key points:

• Reverse the sequence of removal as close as possible. This will generally lessen errors involving the removal of a newly installed component to allow reinstalling another. (Remember assembling the kids' bicycles without looking at the direction sheet?)
• Make sure to route wiring along the same original path because proper routing is very important for the electronic system to operate properly. Induced voltage can occur if wiring is improperly routed, and this can happen especially if wiring is laid parallel to another set of wiring or circuitry. Wiring that's susceptible to this condition is generally routed at perpendicular angles (90 degrees) to each other.
• Attach mounting clips in the same location. During disassembly, careful removal is necessary to not break or damage the retaining clips. These mounting locations are normally predrilled or stamped, which allows for easier reassembly since the mounting holes are already there as a guide.
• Ensure a proper ground is available to the component if required. Many electronic components may use a case ground, with an electrical diagram indicating this by a ground symbol (y) attached to the component outline. Many times this indicates the mounting bolt will ground the component for proper operation.

If there is a ground wire, the wire terminal may include a special fastener that may have a specific side to contact the body to ensure proper grounding. This type may include a rougher side that will "dig through" the paint and primer to get proper contact with the metal surface.

The fasteners may also include special mounting washers and coated retainers.

Note: During disassembly, proper organization of the component and fasteners together in a parts bag will greatly improve the reassembly process.

• Properly torque the fasteners if required. Many sensors have specific torque specifications to ensure secure mounting and grounding. Automotive service manuals and third-party guides will generally identify these specific requirements when necessary, and instruction sheets may also be included with new replacement parts.
• Replace mounting fasteners and retaining clips with "like kind and quality." Many safety-related components require replacement of the mounting hardware along with the new component, and this may be true for many other mechanical-related systems as well. Vehicle manufacturers generally provide this documentation in their service manuals.

If new fasteners or retaining clips are needed, they must match the original equipment manufacturer (OEM) specifications. This may include grade, pitch, length, type and coatings. Don't go to your bolt drawer or can for replacements that look about the same.

• During rewiring, it may be necessary to add more dielectric grease to the connection to ensure proper sealing from moisture. Many options are available, but it's best to use recommended products from the OEM.
• When using dielectric grease, make sure proper connections are obtained. Doing a voltage drop test across the connection (covered in the next section) can indicate improper connections.

Repairs
Following a collision, it's common to run across damaged wiring that must be properly repaired or replaced. Proper repair includes proper tools, connectors and procedures. This article's scope is not to explain all, but to look at some important considerations.

Each vehicle manufacturer may differ as to what area of the system can or cannot be repaired. Typically, manufacturers differ the most on safety-related systems, such as passive restraints (air bags included), and some manufacturers have specific guidelines about the repair of the main wiring harness. Service manuals and third-party system-specific manuals do a great job of indicating these special guidelines.

In general, the common guidelines are:

• Manufacturers normally don't recommend the repair of any wiring from the component's connector to the component itself for safety-related systems. This "pig's tail" may be very long to route around another component. In any case, it's not normally recommended to repair.
• Recommended methods of repair of other wiring areas vary. Options may include soldering and/or special connectors.

Soldering - Some manufacturers approve soldering as an acceptable method of wire repair. But there are a few important considerations to be aware of when soldering: First, the preparation of the joint is as important as the preparation for properly welding in a structural rail. The properly prepared wires are normally twisted together in what's known as a "Western Union" joint. The wire is heated with a soldering iron, and solder is then melted to the joint.

It's important that the soldering iron used doesn't damage the circuitry or component. Around sensitive circuitry, I-CAR recommends using a soldering iron at approximately 15 watts. This low wattage will keep the heat contained and will have very little EMI, but it will be able to melt the solder during the operation. In addition, the solder used should be of a small diameter (requiring less heat) and be flux core, not acid core.

After the joint has been completed, it must be sealed from the environment. This, generally, will include a special filled connector or a "shrink wrapping connector." In most cases, the connector must be installed to the wire before joining.

Connectors - Besides soldering, many manufacturers recommend the use of "solderless" special connectors, which are used to join the wires together and seal them from the environment. There are probably as many special connectors as there are different wires on a vehicle, and many have come to be available from other industries. But, keep in mind, these connectors must be designed for automotive use and be acceptable to the vehicle manufacturer's needs.

These connectors generally require a special tool to properly join the wires and seal the connection. One type commonly used includes a butane heat source to melt the connector to seal the joint.

• In any repair or connector, it's important not to add excessive resistance to the circuit. If the joint isn't properly sealed, the joint will corrode and can increase the resistance of the joint, which can cause many problems - including false readings of the diagnostic mode of many systems, improper operation of the component and possible replacement of the wrong parts.

A voltage drop check is used to determine if excessive resistance is present through a connection or repair. To take a voltage drop check, measure the voltage from both sides of the connection or repair joint. If the readings vary greater than .1 of a volt on the "hot side" or power side of the circuit or .05 of a volt on the ground side of the circuit, the joint or repair needs to be checked for loose connections, corrosion or poor repairs.

Make sure the readings are taken with a DVOM with at least 10 mega-ohms of impedance. Any less could cause serious damage to sensitive electronic circuits.

• If individual wires in a group require replacement, replace them with the same diameter, type and length. Circuit requirements determine the wire diameter needs, so make sure not to change this. It's also very important to match not only the diameter, but also the wire used (copper or aluminum) and type (solid or strand).

Verification
Once all the components are properly reinstalled and the wiring has been routed as before, the repairs still aren't complete until the systems are checked for proper operation - which includes resetting radio stations or any other personal settings.

Most electronic systems today have self-testing capabilities and automatic warning systems. Warning lights are no longer "idiot lights" as we've been accustomed to for many years. In fact, in some systems they can be used to diagnose where the system problem exists. Service manuals and third-party, system-specific manuals offer troubleshooting procedures that are easy to follow and may only require minimal equipment, such as a DVOM (depending on the manufacturer and system).

Scan tools also can normally verify the system operation and may be necessary to remove system fault codes on many safety-related systems. These tools are very valuable for many of today's electronic systems.

A very important point to keep in mind is that some systems need to "relearn" their function. A common example of this is with some driveability systems. Some vehicles, after the battery has been disconnected, will run very rough initially until the system relearns the operation from sensor input.

To correct this, the vehicle should be driven a few miles until - miraculously - it begins to drive fine! Check footnotes and other service bulletins for information involving these vehicles. Otherwise, you may spend hours rechecking everything you've done only to find that it now works fine.

Wired
The key to rewiring a vehicle is to have procedures in place during disassembly so that once the time comes for reassembly, there's no guesswork involved.

Guesswork leads to errors and efficiency loss - not to mention lost profits. And, in today's competitive marketplace, a collision repair business that guesses about repairs isn't going to stay in business for long.

Writer Tony Passwater is a long time industry educator and consultant who's been a collision repair facility owner, vocational educator and I-CAR international instructor; has taught seminars across the United States, Korea and China; and is currently an industry consultant. He can be contacted at (317) 290-0611 or (Tony.Passwater@aeii.net).