Sanstec Design Blog

I've recently had to undertake some basic electrical fault finding on one of our trailers in the sanstec workshop. After completing various jobs and updates on it, which included some tidying of the wiring for the towing lights, a problem occurred where all the trailer lights would come on all the time all at once.

The lighting board at the back of the trailer and necessary for any towing, is essentially a piece of plastic board with an arrangement of lights fitted to it which meet the appropriate requirements of the law to allow you to tow the trailer during the night and day. The lighting board itself consists of a few wires in a cable, connected to a plug, which connects the lights at the back of the trailer to the tow vehicle via the relevant socket.

With some previous experience of similar problems, it looked very likely that the earth wire wasn't making a good connection somewhere in the arrangement, leading me to check for continuity of the various wires in the cable. A continuity check is essentially the process of establishing whether or not one end of the wire is actually still connected to the other end, by using, in this case, an electrical test meter set to measure ohms (Ω).

Surprise surprise, the earth was the only wire that was showing a complete lack of continuity in the cable arrangement and therefore undoubtedly was the cause of the problem. Fundamentally, there was a break in the wire somewhere. A break, which was going to be very difficult to find over the five metres that the wire ran through the cable. Time for a completely new section of cable then!

It's possible that there may be several breaks in the wire in the trailer cable, but it only takes one tiny disruption along any of the wires to create a total loss of communication (electrical flow in this case) throughout the entire length and, therefore, subsequently, causing all sorts of problems as a result.

The fact that this one wire was causing this much trouble got me really thinking about how important it is in Design Engineering to make sure that you keep continuity between the various stages and processes that you are dealing with. In terms of the general processes involved when working with a new product, concept or idea and bringing a 'device' into being. All of these aspects need to be carefully connected to each other to make it work and be successful.

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