12V Guru – Fixing Faulty Lights

Question to 12V Guru:

Hey 12V Guru – we have purchased a secondhand van that is at least 15 years old and we keep having issues with lights not working – do I need to go to LED’s and refit the entire van?

Paul Essary, Shoalhaven Heads, NSW

12V Guru answers:

Hi Paul, Lighting can certainly be one of those annoying and niggling issues in most caravans regardless of whether it is old or freshly off the lot from a dealer.  The fact that your van has a bit of age on it should not be the issue, it is most likely that you will need to check and maintain a few simple things to get them working. Unfortunately, they have not yet made a caravan that is maintenance free!

It is unlikely that you need to move to LED’s and the issue will most likely be with in your wiring somewhere.  Whilst that sounds like a daunting task with all that black cabling running through the van including the walls – it’s probably not!  It is reasonable to expect that the lights on your van having been working fine for the previous owner.  A few basic tools, a multimeter and some sandpaper and your lights will no longer be an annoying hassle.

Should I move to LEDs?

Whilst older style bulb globes with the filament inside are becoming a thing of the past these is no need to replace them unless you have issues or concerns with how much power they draw from your battery.  They are certainly not as power efficient as the new Light Emitting Diodes (LEDs).  We have often heard the comment … “the bulb globes rattle loose and don’t have a good connection” but this is unlikely as the wire contacts inside don’t weaken over time. It is more common that either the globe is just old and needs replacing or a connection issue.

Common reasons for faulty lights

The most common of reasons why lights, inside or out, are not working or at best are intermittent, is that there is not a good ground for the electrical circuit.  The caravan chassis which is made of steel will have been wired as the electrical ground for the 12V circuitry. The cabling from the trailer plug at the back of your vehicle will contain an earth return wire and this will in most wiring setups be wired directly to a clean metal ground point on the chassis.

The first step is to eliminate a damaged cable.

The two main causes of a damaged cable are:

  • firstly the copper wire has become exposed as it has been scraped by something or that it may have been penetrated by a screw or staple. Check all wiring if possible, to identify if this may be an issue.  For example, if a staple or screw has inadvertently gone through wiring it creates a short circuit (the path of least resistance) and your lights will not work.
  • The second potential cause for concern in your wiring is, broken connectors which join wires.  Where there are identifiable connectors gently see if any of the wires pull away from either side.

Next step is to identify if there is a grounding issue. 

Your lights will need to be grounded somehow back to the chassis.  This will be either through a wire from the lighting circuit back to metal connected to the chassis or it will be a return earth wire.  If you have checked all possible wiring looms as per previous it is unlikely to be the earth return wire and more likely that as your van a little age on it, that the earthing point for the light has a degree of corrosion that has crept in.  This corrosion will prevent a good electrical connection and show itself as faulty lights. 

The light is not faulty, just the wiring connection needs some maintenance.  Using your multimeter to identify where the breakdown in the grounding is and then grab the sandpaper or wire brush to clean up the earth connection point. For those new to multimeters – don’t be scared. Grab an “el cheapo” from a hardware or auto store and check out how to use it on YouTube.  It is super easy and really is an essential part of your travelling toolkit and saves a costly trip to the auto electricians. Remember to keep an eye on the voltage and don’t let it drop below 12.1Volts.

Safe travels – 12V Guru

The article has been published in the Caravan World Magazine.

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