Keeping Your Trailer Safe on New Zealand Roads: A Guide to Checking and Fixing Electrical Connection Problems

New Zealand is a country that relies heavily on trailers, with more than 650,000 registered trailers on its roads. With such a significant number, it is essential to keep these trailers in good condition to ensure their safe and reliable operation. Here, we discuss electrical connection problems, how to check for them, and some simple solutions to resolve them.

Electrical problems are a common issue with trailers. In New Zealand, trailers must have working lights, and many bigger trailers with electrically controlled brake systems also rely on a fully functioning wiring system and plug connection.

    Start by checking that your trailer plug is functioning correctly.

  • Check for overall damage. The plug is designed to keep water and dirt out, and cracks can allow it in. Plugs are not difficult to replace, and most will have the wire colour and function explained inside the cover. If replacing the plug it is a good idea to take a photo of the wiring layout in the old plug before removing it, then matching it to the new one.
  • Check the connection pins are intact. To enable the good contact, they are not solid but split into halves or quarters. All sections of the pin should be present, and the whole plug will need to be replaced if any pins are damaged or missing.
  • Ensure a good connection – this can be helped by slightly spreading the sections of the pins apart. This ensures contact with the mating receiver pin on the vehicle socket. Be careful not to overdo the spreading, as pins could break.
  • A good connection requires the tow vehicle socket is also sound. Without a trailer connected, these can be prone to getting dirty, and this will impact the connection quality with the trailer plug. Clean it out if needed and look for obvious damage at the same time.
  • Open the plug cover, and check for loose wires by gently pulling them; not with enough force to pull the wires out, but be looking for loose connections. If needed, tighten the screws that hold the wires in place, but avoid over-tightening that could cut through the wires or strip the screw threads.
  • Once the trailer plug and vehicle socket check has been done, it is important to couple the two together properly. There is only one way they will connect, but the socket cover also acts as a plug retaining device, so is important that plug is all the way inserted, and that the socket cover engages with the plug to prevent it falling out while traveling.
  • When the trailer is being stored, it is a good idea to stow the plug away from potential damage. Many trailer builders will fit a plug holder, and ideally these would be positioned so the wires are not facing upwards, which will help avoid water running into it if the trailer is stored outside.

    Other wiring issues do arise from time to time, and other checks can be carried out to resolve them.

  • Check the condition of the wiring. Trailers are prone to stone impact damage, and exposed wires should be inspected visually. Repairs that are intended to be permanent (if needed) will require a matching type of cable and some specialized tools, so is beat carried out by a qualified Auto Electrician or mechanic.
  • Check where wires are fastened to the trailer and where they pass through the trailer chassis components. Trailers will typically have more vibration than a car or truck, and these areas can chafe at the wires if they are not held tightly. Remove these wear point where possible. Zip ties are a fast and easy way to eliminate this issue.
  • Check connections at the lights. Some lights are supplied with long cables, and don’t have a join near where they are. However, many do, and the quality of the connection can be checked by having the lights on, and slightly moving the joins about. It will depend on the connection used whether this is a DIY or expert fix. Connectors using screws will be serviceable, but soldered joins will require specialized equipment.

For the low cost and peace of mind when towing, Trailparts strongly recommend that a professional goes over the wiring system and makes any needed repairs. Trouble shooting is easy if there is a consistent fault, but often wiring issues are intermittent. If your trailer is fitted with electric brakes, they do require the wiring to be working 100% if they are to perform the safety function they are designed for.

By following these simple steps and seeking professional help when needed, you can ensure that your trailer's electrical system is in top condition, providing you with a safe and reliable towing experience on the roads of New Zealand.