I wanted to install a rear working spot light. It’s function will be to provide more light for situations where it was dark and we need to set up camp or do any other task which requires visibility for short periods in the dark.

The working light is not intended to be for lighting the camp in the evening, in my view this would defeat the purpose of camping, be rude to neighbours, be too bright and flatten the aux battery too quickly. After we have cooked we generally chat and drink with only a small candle (tee-light) in a jam jar. This is more than sufficient and provides ample light to locate the beer where ever it was left or camp site after a pee. Too much light stops you seeing the beautiful night stars.

The working light is mounted on the rear of the vehicle near the top of the roof line and is adjustable in direction. It is a 55 Watt Wipac unit. With hind sight, I probably should have purchased an LED unit, this would have been more efficient battery usage wise. C’est le vie.

There are many ways to set up the electrics on a light, options include wiring directly to the light with a single fused cable, this is ok if the light has a switch, but I was not happy with having an externally operated switch and no isolation within the vehicle.

The second option is as per above but mount a switch in the cab. This is not very tidy in terms of electrics as you are switching a slightly high current and this has many side effects, but is manageable.

The prefered option is to switch the light via a relay or contactor. In this case as the current is only on the order of 4.6 Amps (I = P / V = 55 / 12) I would use a relay. Most vehicle relays available off the shelf would more than cover this. The basic layout for the wiring discussed here is shown below (Rev A). This was my original planned method.

What I actually ended up doing was as shown in Rev B below.

The reason I changed the diagram or method of wiring this was because.

• I wanted indication in the cab the light was on.
• I wanted to minimise cable runs to the switch.

The Rev B diagram is a nice alternative because the amber LED (Light Emitting Diode) is only illuminated when the ignition is on. I don’t care if the light is on with the ignition off as I will probably be able to see that and be using it. To feed the LED I choose to use the cigarette lighter feed in the dash as this is already switched by the ignition, and handily local to the switch mounting position I intended to use.

The second reason Rev B is good is that I only need to run a single wire from the battery box to the dash. This is because I am switching the negative side of the circuit and because of this I can earth it locally. I chose the cigarette lighter earth wire, it was handy and local.

When I installed the wiring for the auxiliary battery and additional sockets around the vehicle, I was careful to use conduit. This is routed along the chassis rails and enters the vehicle in the tail light enclosure in the same manner as the trailer wiring etc. It required no holes drilling. The advantage of the conduit is that it makes it very easy to pull in additional wiring.

The relay for this installation is mounted in the battery box near the auxiliary battery fuse panel. I have a conduit running from the battery box to the centre dash. This allows me to run wires easily and not worry about chaffing etc. I plan to pull in two more wires for the battery gauge soon. This will allow me to monitor the health of both batteries with one gauge with a toggle switch.