Appliance Cable Wiring Harness

The term ‘harness‘ is used for all of the wires that connect the various components within an appliance. In large appliances they are usually bound or fastened ‘together in bunches to keep the wiring neat and safely anchored. Smaller appliances, however, may sacrifice neatness for safety and route the wiring to avoid contact with heat or sharp edges. The correct positioning of wiring also contributes to the double insulation of an appliance, so no alterations whatsoever should be made to the routing or position of the wiring in double insulated appliances.

When you first take a look at it, the harness may seem like a jumble of wires thrown together, but if you take the time to inspect it, you will find that each wire is colour-coded or numbered either on the wire itself or on the connector at each end. This allows the engineer to follow the wire through the appliance easily. With a little practice, any wiring or coding can be easily followed.

Common Appliance Cable faults

The connecting wires to and from a component are essential to it and possibly to other components that rely on its correct functioning. Luckily, wiring faults, other than flex faults, are not very common. When these faults do occur, they may seem to cause major problems when, in fact, the fault itself is only something really quite small. For example, a single poor connection can cause a motor not to function at all, rendering the appliance totally unusable.

Do not fall into the trap of invariably suspecting the worst. Many people, including engineers, blindly replace major components, such as a motor or a heater, only to find that this does not cure the problem. Stop, think and check all wires and connections that relate to the particular fault. Always inspect all connections and ensure that the wire and connector fit tightly. Loose or poor connections can overheat and cause a lot of trouble, especially on highly rated appliances such as heaters. Poor connections in items such as vacuum cleaners and hairdryers will be aggravated by the movement of the appliance when it is being used. They may not be so apparent when a testing.

One of the most easily missed faults is where the metal core (conductor) of the wire has broken but the outer insulation has not. This wire appears perfect from the outside but will pass no electrical current. If you find a break or crack in the insulation, renew the whole of that flex. Do not simply tape or join the damaged flex at that point. As with all repairs, ensure that the appliance is completely isolated —switch off, plug out — before any repair or inspection is carried out.

Bear in mind that such faults may be intermittent. A meter reading may be correct on one occasion and the same test later may prove incorrect. This is due to the movement of the outer insulation of the wire first making, then breaking the electrical connection.

When testing for such intermittent faults, it is wise to pull or stretch each wire tested: an unbroken wire will not stretch but a broken one will stretch at the point of breakage. If it is an internal wire, rectification is a simple matter of renewing the connection with a suitable single wire of the correct rating fitted with suitable connectors.

1. Make notes before removing components so that you can ensure that the harness/wiring is correctly routed as it was originally.
2. Do not rush stripdowns or repairs. Double insulation relies on the correct and precise positioning of each wire and component.
3. Take care that any metal fastening clips do not chafe the plastic insulation around the wires.
4. Make sure that wires are not in contact with sharp metal edges, such as self-tapping screws.
5. Before attempting to remove or repair the wiring harness or any other component in the appliance, isolate the appliance from the main electrical supply by removing the plug from the wall socket.

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