Section III . ELECTRICAL WIRING

TM 750-245-4

Section III . ELECTRICAL WIRING

3-10. General

(4) For a solid wire splice, cut back the

This section covers the inspection of electrical wiring,

minimum of insulation, place ends of wire in stakon

cables and wiring harness assemblies.

Cable

splice connector, solder and crimp.

assemblies are identified as interconnecting cables

b. Insulation.

between two assemblies. Wiring harness assemblies

(1) An appropriate cable test set or megger

are identified as internal wiring which connects chassis

can be used to determine the insulation resistance. If

internal components. A discussion of electrical cable

insulation requirements for the subject cable are

and wiring harness repair is covered to give the

unavailable, reject on values less than 100 megohms.

inspector a better understanding of what he is to look for

(2) Check cable shielding to insure proper

during inspection.

grounding of the shield.

(3) Small holes in vinyl sleeving may be

a. Insulation of electrical wiring is done to prevent

patched by cementing on a patch of similar material,

failures, grounding, and to keep out moisture which

using vyna-kote cement. Larger holes may be repaired

could cause shorts. Insulation in many cases is used to

by slipping on a length of solid sleeving, or by using split

prevent electrical shock to personnel and to prolong the

sleeving large enough to lap 180 degrees. In both

life of the electrical equipment.

methods, cement with vyna-kote.

b. All splices and connector terminals should be

(4) Rubber cable jackets may be repaired by

insulated and in most cases preshrunk in place. The

patching and vulcanizing.

insulation should extend 1/4 inch beyond the connector

(5) Plastic cable jackets may be repaired with

pin or wire which it insulates. It should not be cracked,

epoxy cement with or without a patch, as necessary.

torn, checked, or rotted.

(6) Conductor splices should be coated with

c. Insulation covering cable assemblies and

liquid vyna-kote and then covered with vinyl covered

connector ends of wiring harnesses are generally of two

braided glass.

types; nonshrinkable and heat-shrinkable.

Cable

c. Connectors. The connectors used on cables are

assemblies are usually completely covered by an outer

of many configurations and no attempt is made here to

insulation material; vulcanized rubber or neoprene.

describe them in detail.

Solderless wire wrap

Wiring harness assemblies usually have a "spaghetti"

connections are permitted in certain instances of

type insulation which can be slid over the wire

communication and control circuits where terminal pins

assemblies to cover the bare connections.

are designed for this type connections. When repairing

or replacing connectors, care must be taken to observe

3-11. Cable Assemblies

the order of disassembly of the parts so that they may

A cable assembly consists of two or more electrical

be reassembled in the same order. On multi-conductor

wires enclosed in a rubber or plastic cover or jacket.

cables a template should be used to identify the

The ends usually terminate in pin type connectors. To

conductors while the connectors are being changed.

assure a good quality cable repair, in-process inspection

Care must be taken to orient or polarize the terminals to

is necessary.

assure proper mating of the connectors.

a. Splicing.

(1) Cables may be spliced and used provided

(1) Ends of conductors will be sold-red to the

the length is not reduced beyond 90 percent of the

pins and sockets using a noncorrosive flux. The quality

original length. (See paragraph 3-11 b for splicing

of soldering is described in chapter 7. Clean the

procedure.) If the cable is to be returned to the using

connector by immersing in trichloroethylene and

unit, the minimum length is determined by operating

brushing between wires, pins, and other components.

conditions. Conductor splices will be soldered unless

Fill backshells, or hoods with sealing compound or

.specifically prohibited. Missile cables are normally not

epoxy resin if required.

spliced.

(2) In the event that the jacket has shrunk

(2) Splices will not be made at flexing points.

away from the connector, disassemble the connector,

Splice in a new piece of conductor with joints on either

pull the jacket into place against the connector and

side of the flexing point.

Spliced joints will be

secure by winding the linen thread.

strengthened by additional sleeving or lacing.

(3) Damaged or dirty threads on the

connectors may be made serviceable by chasing the

(3) For a stranded wire splice, the strands

threads with a die or tap.

shall be combed out, interlaced, compressed, and

soldered. For a nonsolder splice, twist the strands, trim

and use a splice connector ("Sta-Kon, two way, butt end.

3-2