Before we add aux equipment to the D90 we wanted to create an electrical panel designed to fit our needs while not taxing the OEM fuse box or electrical system. This meant adding an aux fuse box and some relays that are wired into the battery without going through the OEM system. This will allow us to add some switches to aux gear and upgrade the stereo system. Since this is an off-roader and run about we don’t need a full overlander system…..for that we have the Sprinter Adventure Wagon. So for the D90 we planned to add some off-road bumper lights, winch, air compressor, upgraded stereo, and enough open slots for future roof rack lights, seat heaters and 1-2 other things.
The first decision was where to put this gear as Defenders are short on space. The battery box under the driver seat had enough space and made the wiring clean and accessible. The driver seat simply lifts up and you can easily access the battery box in seconds. We didn’t want to simply throw gear in the battery box so we built a wood panel that is bolted to the metal wall of the battery box and then mounted all the aux electrical gear to that wood panel. This allows us to build and wire everything outside of the truck and then simply bolt the whole panel in.
We wanted to make it as clean as possible with as few wires as possible with plenty of protection for the battery and systems. The relay systems were built by MGI Speedware who offers extremely nice car electrical components. The fuse box is made by Blue Sea. Here is what the panel includes:
positive power distribution block that hooks up to the battery
relay control box with 4 relays, this also has an inline fuse for the unit and dedicated fused for each relay
a dedicated relay for the air compressor due to the high load, this also has its own inline fuse
a fuse box with 6 slots that are all individually fused and the unit has its own inline fuse as well
a negative distribution block that grounds to the chassis
The relay control block will allow us to hook up switches for the bumper lights, future roof lights and seat heaters while giving us a couple slots to tap into in the future as needed. The single relay for the air compressor is designed for high load motors. The fuse box will give power to the stereo amp and any other future gear we can think of.
Because we like clean wiring, we decided to install battery terminal distribution blocks so that we don’t need to stack up connectors on the battery terminals. We found a great solution with SDHQ who makes solid block battery terminal distributors where you can easily bolt on multiple connectors. This way we can have the winch, the OEM systems, and the aux panel all wired directly to the battery terminal but on separate mounting points.
In the end I will admit this was a bit overkill to add a few aux equipment. But The goal was to do it once and for it to be ready for any future needs.