Wiring Harness Repairs
WIRING HARNESS REPAIRSIn many cases wiring harness damage due to burnt, corroded or cut wires and broken connectors or terminals can be easily repaired. Repairing rather than replacing a wiring harness can avoid excessive vehicle down time waiting for a replacement harness, and if performed properly will provide trouble-free service.
REPAIRING OPENS
Once you have determined which portion of the circuit contains the open, one of two repair methods can be utilized after disconnecting the battery.
The most desirable repair entails pinpointing the exact location of the break. This can be accomplished with a self-powered test light or ohmmeter by connecting one lead to the terminal on the end of the wire in question. Use the other lead or the point of the test light to probe the wire (by piercing the insulation) every few inches. Continue along the wire until you lose continuity (the test light does not light up or ohmmeter reads infinity ohms). The break is located between the point where the wire last showed continuity and the first point it did not. The wire can then be cut, spliced, and soldered. For details on this operation see "Splicing Copper Wire." Wiring Harness Repair Methods
Please note that the use of butt connectors should be avoided, especially in areas where vibration and moisture are prevalent, unless soldering the wire is very impractical;
Another method of correcting open circuits is to completely bypass the open wire with a new one. This operation should only be performed when a wiring harness is inaccessible, making it difficult to pinpoint the exact location of the open. The following rules generally apply when bypassing an open wire:
1. Use only the same wire gauge as the original (refer to the wire gauge comparison table found elsewhere in this text).
2. Replace the entire wire from connector to connector. The only exception is when the wire runs to a splice in the harness. In this case the harness will have to be opened and the new wire soldered to the existing splice.
3. Use only the proper size and type terminal to lock into the connector.
4. Use wire tags to identify new wire with the original wire's color code.
5. Route new wire as close to original harness as possible. Tape new wire along original harness. This will allow easy identification of new wires if any subsequent work is performed on the vehicle's electrical system.
Occasionally an open will be located at a wire terminal from an improper crimp or the terminal is crimped over the wire's insulation. This is most easily repaired by removing the terminal from the connector, cutting off the old terminal, and installing a new terminal. Proper crimping procedures must be used.
NOTE: SRS HARNESS MUST NEVER BE REPAIRED.
REPAIRING SHORTS
Repairing a harness that has been damaged as a result of a short circuit can be more difficult than an open, as there are usually several burnt/melted wires with damaged terminals and connectors. However, repairing a wiring harness that is not excessively damaged may still be the most expedient way of putting the vehicle back on the road.
1. If at all possible, the harness should be removed from the vehicle and repaired on a bench for easy access to damaged wiring.
2. Remove the wiring harness wrap well beyond the visibly damaged section and inspect remaining wiring for hidden damage. When working with taped wiring harnesses it may be easier to slice the wrapping than to try to unravel it. This can be done using a razor blade or sharp knife however, wiring that is still serviceable may also be sliced. A good alternative would be the use of a seam splitter, which is readily available from fabric or sewing supply stores. Seam splitters will cut the harness wrap but, due to their design, will not harm the wiring.
NOTE: When replacing wires from terminal to terminal, be sure to color code the new wire to identify it.
3. When splicing two or more wires in a harness, stagger the splices to prevent the harness from becoming excessively bulky in the area of the repair.
4. Each splice should be insulated before the harness is re-wrapped. This can be done one of two ways, with either electrical tape or heat shrinkable tubing. If the splice is among several other wires in a harness, it may be very difficult to wrap electrical tape neatly around the splice. Therefore, the use of heat shrinkable tubing is the preferred method for insulating a splice. To install heat shrinkable tubing:
A. Locate tubing of the proper diameter. The tubing should have a snug fit over the splice when it is completed. This means the tubing will have a slightly loose fit over the wire insulation as the splice usually has a larger diameter than the wire.
B. Cut the tubing to the proper length. The tubing should be long enough to cover the splice and extend up the wire in each direction about 1/4 inch.
C. Slide the tubing over one of the wire ends prior to joining the wires for the splice.
D. After soldering the splice move tubing into place and shrink with a heat gun.
5. After completing all the necessary splices, check all repaired wires from connector to connector with an ohmmeter. A copper wire which has been spliced correctly will have a resistance of 0 to 0.02 ohms, depending on its length and diameter.
6. Electrical tape can be used to re-wrap the harness. Start a few inches below the repair - to overlap original harness covering. Wrap tape in the same direction as the original harness covering, overlapping each turn about 1/2 the width of the tape. Continue a few inches beyond the repaired area. NOTE: Some harnesses are covered with a plastic conduit. Be sure to reinstall this where applicable.
7. Reinstall harness in vehicle and check operation of all affected circuits.