What A Tangled Web We Weave: Re-Installing Electrical Components and Wiring - BodyShop Business
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What A Tangled Web We Weave: Re-Installing Electrical Components and Wiring

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?



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"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

  • 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.
  • 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.

  • 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.

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    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.

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    The fasteners may also include special mounting washers and coated

    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

    • 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.


    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.

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    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

    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

    • 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


    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


    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.



    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
    ([email protected]).

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