LET THERE BE LIGHT WIRING AND ELECTRICAL ISSUES Words and Photos Stuart Francis
Good wiring should discretely blend into the background of the vehicle however we have all seen wiring that doesn’t.
34 Beaded Wheels
The psychedelic spaghetti that seems to have been strewn around the engine bay or frame by a partially sighted colour blind chimp. The excess cable bulging behind a cover, cables so tight you could play a tune on them or, horror of horrors, household wiring cable. To add to the eyesore; modern coloured crimp connectors, badly made splints and splices, tap splices (Scotchlock) and my pet hate, chocolate block connectors. The final indignity is these abstract wiring looms are usually held together by multi-coloured vinyl tape (invariably starting to unwind), masking tape, sellotape and in one instance butchers string. It doesn’t take that much effort or skill to tidy up a wiring loom so that it blends in and is more reliable; the following are some practical pointers that might help. Included are some thoughts on how to improve the performance and reliability of a wiring loom and electrical systems. Most vehicle wiring looms were built down to a price (copper costs money) and were adequate for their original intended use. Each joint, connection or switch contact is a small resistor that consumes power and drops the voltage, even the cables themselves have a slight resistance. The effects of aging
and abuse (like fitting oversize headlamp bulbs) have eroded what margins there ever were. A good test of a machine’s electrics is to turn the headlamps on full beam without the engine running and check the voltage across the battery and then check the voltage across the bulb contacts. Even on a good system there will be slight difference, usually some millivolts. However if the voltage difference is nearer a volt or more there is a significant problem. It is then worth checking the voltage drop from each side of the battery. Always give the battery terminals and connectors a good clean. The most common cause of voltage drops in older machines is earthing issues. To save on cabling costs manufacturers used the chassis or frame as the earth conductor. This worked well when everything was new and shiny, however years of rusting, road grime, corrosion, and painting gradually take their toll. Riveted or bolted up chassis and frames are particularly vulnerable to this type of slow degradation. The main problems are with the high current drains. You can go through the tedious process of cleaning all the earth connections but there is a better way. Run dedicated earth cables from the battery to the headlamp, taillight and
