A Super Simple AWESOME Off Grid 12V System... Step By Step With Diagrams PART 3

Updated: Jun 16

Hi everybody and welcome to PART 3 of our awesome set up, if you are just joining us at PART 3 and have not seen PART 1 or PART 2 of our post yet please follow the links below to so you can see how we got to this point.

if you have already read the previous posts and are already caught up we are just going to jump straight back into it.

At the end of PART 2 we had just finished filling one side of your blade fuse box and you should be left with a set up looking something like this...

To make things easier again we are going to zoom back into the fuse box so we can finish wiring our accessories to it...

The next thing that pretty much everybody wants in their campers is a powered roof fan.

Roof fans are very important in a van build for ventilation, fresh air, extracting smells & fumes and with some adding a little bit of day light for the day times, there are a few good ones on the market but (in our opinion) the best one and our suggestion for this build is the Maxxair Delux.

Not only are these fans unique in the fact they have a built in rain cover so they can still be used in the rain but they also are one of the only fans on the market that can both extract and blow.

They do have a downside though they stick up quite high so if you are trying to be stealth this fan probably isn't for you.

Maxxair Maxxfan Deluxe 400 × 400 Rooflight Clear Tint Remote Control Rooflight


These are very easy to hook up and you already have everything you need to do it.

So first find your 21 amp twin core cable and run a length long enough to reach from your 12 way fuse box to your roof fan, at the fuse box end attach two ring crimp connectors and connect the negative (black) cable to any negative terminal on your fuse box and the positive (red) cable to any positive terminal on your fuse box.

Please see picture below...

Next at the fan end of the twin core cable attach one of these to the both the positive (red) cable and negative (black) cable and crimp into place... see pictures below.

Now you are going to have to connect the cables from the roof fan to your cable and to do that you are going to need to know which cable is positive and which cable is negative.

Just to make things a little bit more complicated the cables coming out of your Maxxair fan will not be black and red they will be black and white, common sense will tell you that black is negative as it has been for everything else so far but with this accessory it is not the case.

When it comes wiring your Maxxair fan black is positive and white is negative, as the background for the wiring diagram is also white for the sake of the wiring diagram this cable will be Green...

please see picture below...

Again the last thing you will need to finish the circuit is a fuse

Maxxair fans are built for 12v set ups so we don't really need to do any maths to work out how many amps these will pull as the they already tell you in amps

Set on the highest fan speed the Maxxair fan draws a maximum of 5 amps and the cable we have use is 21 amp so for this set up we are going to use a 10 amp fuse.

Once you have inserted your 10 amp fuse into your 6 way blade fuse box you should have something that looks like this.

Please see picture below...

The next thing we are going to add to the set up is a kitchen tap, a pump for your water and and a gas hob that needs to be wired to the fuse box for the spark/ignition.

Before we do that though we would just like to tell you that we have our very own Van Build facebook group where we share lots of our awesome content, exclusive content and starting this week video content too as well as answering any questions you might have for us. Please click the photo below and join our van build group if it sounds like something that interests you...

When it comes to kitchen sinks there are loads of options out there and you can even make your own out of an old mixing bowl and some decretive piping if that's what floats your boat or you are going for the homemade rustic look.

This is not what we are going to suggest though as the title of the post contains the word SIMPLE and what we just described above is far from.

So for this build to keep things as simple as possible we are going to suggest a Dometic all in one unit and not only is it an all in one sink set up is also has a double hob too 🦜🦜💎 (2 birds 1 stone)

There are a few bits and pieces you will need...

As an amazon associate I earn from qualifying purchases

DOMETIC HSG 2370 Litre Two-Burner Hob and Sink Combination with Glass Lid, 900 x 370 mm


Comet Cold Water Tap 12V Micro Switch Fits Smev Sinks Caravan Motorhome Boat


Whale GP1352 Standard 12V Submersible Electric Pump-White, 13 litres


Everything else you need to wire these bits and pieces to your fuse box you should already have from before. you might be running low on twin core 21 amp cable though so you might need some more of that.

*21 AMP Rated* 1.5mm2 Thin Wall 2 Twin Core Cable Wire Car LED Lights (30M Roll)


Again these are very simple to wire together but you wouldn't think it by looking at it and just to make things even more confusing they all come with different coloured positive and negative cable.

But as I said it is very simple and this is how we do it.

First run 2 x lengths of the twin core 21 amp cable from your 12 way fuse box to your kitchen area then just like before attach some ring crimp connectors to the ends of both the positive (red) and negative (black) cables on each. Next attach each the positive cables to one of the remaining positive terminals and the negative cables to one of the remaining negative terminals on your 12 way blade fuse box.

One of these cables will be for your pump & tap and the other one will be for your hob ignition.

Next find 3 x Wago 221 connectors with 2 x terminals, you should have some of these from the pack we recommended ear.lier in the post.. Please see picture below

Attach your tap to your sink and run the BLACK cable from the tap to one of your Wago 221 connectors.

Next find your pump and attach the BROWN cable to the same Wago 221 connector... please see picture below.

Now take the BLUE cable from the the pump and the Negative (BLACK) cable from one of the twin core cables running from your fuse box and attach them to another Wago 221 connector

And finally take the BROWN cable from the tap and the positive (RED) cable the same twin core cable and attach them to a third Wago 221 connector.

You should have something that looks like this...

To finish off this circuit all you now is another blade fuse, without going into all the boring maths again for this circuit we are going to use another 10 amp fuse.

Next take the remaining length of twin core that you ran from your fuse box to your kitchen area and crimp one of these connectors on both the positive (red) and negative (black) cables... please see picture below.

The cables that come from the hob ignition will be red and black so all we need to do now is crimp the positive (red) cables together and the negative (black) cables together...

And finally to finish off this circuit and your 12 way fuse box you will need another blade fuse.

The ignition will use hardly any power at all and only for a short amount of time so for this we will use a 5 amp fuse

You should now have something that looks like this...

Ok so that is pretty much all of the basics we need running to the fuse box, there are a lot more things we could add to the set up but we want to keep this set up as simple as possible so for now this is where we are going to leave the fuse box.

We have left 3 x spare terminals on the fuse box and these will come in handy if you wanted to add any extra bits to your set up for example another set of sockets, a 2nd roof fan of maybe just an extractor fan for your bathroom area. Obviously everybody's needs are different so the free space on the fusebox will allow you to add your own specific bits and pieces.

For some ideas of what you can add please check out our 12v upgrades post by following the link below...

Ok so now you should have something that looks something like this...

The next thing we are going to add to this set up is another essential for most campervans and that is a diesel heater.

Diesel heaters are literally a game changer and allow you to enjoy and be comfortable in your van all year round instead of just in the summer and even better than that they are cheap to buy, cheap to run and easy to install yourself at home. Who could ask for more.

We're not going to go into all the details about fitting them as we already have a full post dedicated to that so if you want to check that out please click the photo below.

What we will go into in this post is wiring your heater up once you have followed the fitting instructions (we cover it in the fitting instructions post too)

So the first thing we need to say about these heaters is they need to be wired directly to your positive and negative bus bars and not the fuse box. In fact you are meant to wire it directly to the battery via the inline fuse however because of our SOC shunt that we fitted very early on in the build we have effectively just moved the battery terminals to after the shunt in the form of a bus bar so it is the same thing. We can only do this because we used really thick cables at the start of the set up.

If you wire it to the fuse box you are quite likely to get some volt drop and error codes on the heater and you don't want that.

If your heater is further away from your bus bars than the power cable supplied with the heater you need to up the size of the cable or again you will get volt drop. To extend the cable any distance it is best to use 6mm2 cable.




The negative cable supplied with a heater is very short and the instructions for the heater to you to earth it to your chassis. We can't do that as we need it to run through our SOC shunt so we can accurately monitor the battery so you will need some of this




And if you do need to extend your power cable you will need the inline fuse as close to the battery (bus bar) as possible so you will need to cut off the inline fuse provided and add one closer to the bus bar...

In-Line Car ATC/ATO Blade Fuse Holder Waterproof 10AWG



So once your heater is fitted and the wiring loom is connected to the heater, controller and pump it is very simple to wire up.

First we need to run the negative (black) cable from the heater to the same bus bar that we attached our fuse box to. For this you are going to need to extend the short cable provided.

So find your 6mm2 black cable and remove enough insulation from one end to connect a crimp connector.

Please see picture below...

Next find one of these crimp connectors in your crimp connector pack