Wiring Harness Repair Methods
TYPICAL ELECTRICAL REPAIRSAn open circuit is an incomplete circuit. Power cannot reach the load or reach ground. If a circuit is open, active components do not energize. A short circuit is an unwanted connection between one part of the circuit and either ground or another part of the circuit. A short circuit causes a fuse to blow or a circuit breaker to open.
SPLICING COPPER WIRE
STEP 1: OPEN THE HARNESS
If the harness is taped, remove the tape. To avoid wire insulation damage, use a sewing "seam ripper" to cut open the harness (available from sewing supply stores). If the harness has a plastic conduit, simply pull out the desired wire.
STEP 2: CUT THE WIRE
Begin by cutting as little wire off the harness as possible. You may need the extra length of wire later if you decide to cut more wire off to change the location of a splice. You may have to adjust splice locations to make certain that each splice is at least 40 mm (1 1/2 inch) away from other splices, harness branches, or connectors.
STEP 3: STRIP THE INSULATION
When replacing a wire, use a wire of the same size as the original wire, or larger. The schematics list wire size in metric units. The following table shows the commercial (AWG) wire sizes that can be used to replace each metric wire size. Each AWG size is either equal to or larger than the equivalent metric size. To find the correct wire size, use an appropriate wire gauge.
NOTE: If you aren't sure of the wire size, start with the largest opening in your wire stripper and work down until you get a clean strip of the insulation. Be careful to avoid nicking or cutting any of the splices.
Remember that the splice should be at least 40 mm (1 1/2 inch) away from any other splices, harness branches, or connectors. STAGGER MULTIPLE SPLICES.
Check the stripped wire for nicks or cut strands. If the wire is damaged, repeat the procedure on a new section of wire. The two stripped wire ends should be equal in length.
WIRE SIZE CONVERSION TABLE
METRIC AWG* CONTINUOUS
SIZES SIZES AMPERAGE RATING
.4 22 2
.5 20 3
.8 18 4
1.0 16 5
2.0 14 25
3.0 12 46
5.0 10 96
8.0 8 140
13.0 6 285
19.0 4 425
* DENOTES AMERICAN WIRE GAUGE SYSTEMS
STEP 4: TWIST THE WIRES TOGETHER (AS SHOWN)
STEP 5: SOLDER SPLICE (ONLY USE 50/50 OR LEAD FREE ROSIN CORE SOLDER)
Always heat wire with soldering iron and allow solder to flow through the wire of the splice - solder must be shiny when cool.
STEP 6: TAPE THE SPLICE
Center and roll the splicing tape. The tape should cover the entire splice. Roll on enough tape to duplicate the thickness of the insulation on the existing wires. Do not flag the tape. Flagged tape may not provide enough insulation, and the flagged ends will tangle with the other wires in the harness.
PROPER FIRST TAPING:
If the wire does not belong in a conduit or other harness covering, tape the wire again. Use a winding motion to cover the first piece of tape.
PROPER SECOND TAPING:
SPLICING TWISTED/SHIELDED CABLE
Twisted/shielded cable is sometimes used to protect wiring from electrical noise (stray signals). For example, a shielded cable of this construction is used between the ignition and injection ECU's. See drawing for a breakdown of twisted/shielded cable construction.
STEP 1: REMOVE OUTER JACKET
Remove the outer jacket and discard. Be careful to avoid cutting into the drain wire or the mylar tape.
STEP 2: UNWRAP THE TAPE
Unwrap the aluminum/mylar tape, but do not remove it. The tape will be used to rewrap the twisted conductors after the splices have been made.
STEP 3: PREPARE THE SPLICE
Untwist the conductors. Then prepare the splice by following the splicing instructions for copper wire presented earlier. Remember to stagger splices to avoid shorts.
STEP 4: REASSEMBLE THE CABLE
After you have spliced and taped each wire, rewrap the conductors with the mylar tape. Be careful to avoid wrapping the drain wire in the tape.
Next, splice the drain wire following the splicing instructions for copper wire. Then wrap the drain wire around the conductors and mylar tape.
STEP 5: TAPE THE CABLE
Tape over the entire cable using a winding motion. This tape will replace the section of the jacket you removed to make the-repair.
CRIMPING
The plier crimp size is determined by the wire size and insulation diameter.
- larger wire terminals may have to be crimped with slip joint pliers and soldered
- Strip approximately 3 mm (1/8 inch) of insulation
- Insert the appropriate terminal into the special crimping pliers partially close plier to hold terminal
- Insert stripped wire into terminal and firmly close plier
- Repeat procedure for insulation crimp
- Test crimp by applying a pull of 30 Newtons (approx. 7.0 lbs.)
HEAT SHRINKABLE TUBING
The use of heat shrinkable tubing insulation on terminals and wiring repair is recommended. This will ensure that the repair will be properly insulated and will match the factory wiring.
The correct diameter heat shrinkable tubing is cut to length and installed over the terminal and wire. The length of the tubing should be long enough to insulate the terminal and extend over the wire insulation approximately 12.5 mm (1/2 inch). The tubing should then be shrunk to a tight fit using a heat gun as shown. Care should be taken not to overheat or burn this shrink tubing.
Heat shrinkable tubing is available locally in various lengths and diameters.