Afternoon gents

Anyone add an additional fuse box to the interior? I am staying away from those in-line fuses and have a few fuse boxes with multiple fuses that I would like to put inside the car for easy tapping for power in the future. I would like to NOT take apart the dash to mount it, and not be visible unless something got removed or it was well hidden. The only place that comes to mind is the glovebox area, which I am fine with dropping the glove box to check fuses.

The fused circuits I plan on having at this moment are for the heated seats, usb charging, and the LC2 wideband/controller for the incoming MsPnP install. As much as I hate tapping into other circuits, I believe the easiest way for a ign on relay will be pulled from the cigarette lighter.

Also noticed in my car, the interior fuse box #4 does not have a fuse. I assume the pigtail is still on that circuit from the factory to the end plug, then the next connector that plugs into that is more "trim specific". This is just from what I have read from the UK mx5 forums.

Currently trying to get a UK spec MX5 Haynes manual is proving very problematic as no one wants to ship internationally, and the manuals I do find are extraordinarily expensive!

 

Heated seats are a pretty big current draw, and if you're adding an entire fuse box the implication is you want to the capability to draw even more. Why not tap in directly to the battery with a new positive cable, and place your fuse box in the trunk or behind the seats?

I used two inline fuses tapped directly into the battery to power the fuel pump and a 12v outlet I put on the rear bulkhead next to the center console. Once I stop being lazy I'm going to replace them with a tidier fuse box.

 

I wouldn't recommend this placement, but I've done something similar with the cigarette power. Not sure what I was thinking aside from it being hidden and most of the wiring already being in this area. I remember looking for an easier to access location, but struggled to find one that made sense for my setup. Under the steering column or over in the glovebox would probably be easiest to access. The center console might work as well, especially if you could 3d print something to hide it better.


There is a plastic cover that protects the connectors from shorting out. It is not pictured here.

 

Yes. The seat heaters will have a 20a fuse. Same rated fuse used overseas with the stock heaters. My plan is exactly that, run a 4 gauge wire from battery, to 80a fuse, then run 4 gauge down passenger side like some of the stock wiring does. I do not want to run the fusebox in the trunk as running a single 4 gauge takes less physical room than multiple power lines. The 20a circuit for the seat heaters alone is already 1/8" thick with insulation (12 gauge wire + insulation).

I did not think of using that area. I will keep it in mind, the only downside is the amount of tear-down needed to check the fuses if something goes out.

 

Good news! I believe I found a spot behind the glovebox! There are two brackets that hang down with two holes on each side. It looks like it will work, and the back of the glove box is really close to resting on it, if it doesn't already. I have a bracket that I made that will sit an inch and a half back that can hold both the fuse box and the LC-2 controller, and possibly two or three relays if I need them. The gap between the two brackets is 12 inches. I am debating on making it out of some thicker metal as I only had 20 gauge handy. This will work, as I only have to drop the glove box to access the mounted parts and see if a fuse is blown.

Ignore the sun setting messing the camera image. You can see the two brackets hanging down with the double diagonal holes near the top.

 

Behind the seats, on the rear shelf, or in the boot are simpler to implement, easier to access if diagnosing problems.

If you do the above, get a spare glove box, and cut the back of it to give you the access you need. If the fuse box has a cover, you won't have to worry about detritus from the contents getting into the fuses. I did this for mounting something, details now lost in the mists of time ...

 

I like those ideas but would rather not be visible. The distance between the glovebox and the AC box is about 2.5 inches from what I can feel, and only requires removing the glovebox which is toolless.The recessed bracket I made should keep everything in place as stock, so no cutting the glovebox or drilling/taping into things. If the bracket works I will probably end up 3D printing it at work. More pictures to follow

 

If this is a fully loaded daily, I went through the same challenges with several aftermarket parts.

I ended up in two spaces. Tapped off the battery with a large inline fuse to protect the main wire. A distribution block in the PAX side tunnel. This breaks off the main power line to the fuel pump and a USB outlet in the shelf for toolbar mounted cameras.

the main line then goes to a series of relays. I used a bunch of linked relay harnesses that click together. Had I known earlier, I’d have gotten them individually fused too, sorta like this.

https://a.co/d/9Q3RxqG

The series of relays mounted to the firewall. There are a few posts behind the blower fan that I used.

All you really need to do is plan which hot wires need to have power at a specific time and when they can activate another relay (and if a failure may have dependencies).

not perfect, but hidden and not too hard to swap.
.

 

Awesome! Yeah that is about the same way I am going to do things. My plan is to run 4 gauge wire from the battery positive post with an . That would run along the passenger side with the other bundles of wires through the scuff plate trim.

I used my extreme lack of CAD skills and made a bracket that I will be printing. It will mount to the backside of those drop down tabs, and be set back enough to mount the fuse box without interfering. Should be good to hold the , the LC-2 controller, and a spare 30a relay or two on the front side. On the back of the bracket I plan on having this pulling power from the 4g battery cable, then going to the fuse box, being triggered by the Pin J from the options port on the MS3PNP. That pin is 12v accessory @ 0.5a which should be enough to trigger it, and the relay has good reviews on staying powered on for multiple hours on end.



EDIT: I also have , but it is SUPER chunky, so it will just go in my spare electronics parts box.

 

The best bang for buck mod I've done to any street driven Miata is to not waste my time getting the original 12v outlet to work and just mounting one to the rear bulkhead fuel tank area and wiring it direct to the battery. It's an easy way to run or charge anything even with the car off, and can also be used as an easy battery tender hookup if you park your car over the winter. Just imagine that it's done more neat and tidy with better wire routing.

Best of all, no cables crossing over the center console while you drive.

 

Printed, painted, drilled and tapped. I have the 120a relay coming in today and will mount it in the middle spot. I am thinking to mount the relay on the back in case I have another item I need to add later on that needs visible status lights? The paint on the mounting flange was still a bit tacky when I went to flip and paint the other side, but it will be hidden behind the bracket. Not like any of this will be visible unless you drop the glove box anyways, but at least it looks nice. Thanks for the help and ideas guys, I might update this later when I have the time to get the flanges drilled and get this mounted.

 

Crossposting this from M.net but I finished the install this morning:

Finishing this thread off:

Printed out a second bracket, after I forgot to subtract the flanges and it came out 2 inches longer than I needed. Whoops! Good thing my employer is so generous with the resin.

LC-2 Wideband controller on left, Fusebox on right, Large 120A relay in the back.
Ran wiring from battery, to an inline fuse (100A), then through the bulkhead between the cabin and trunk. I put some rubber trim molding around where it came through so it wouldn't rub, but I doubt it would move anyways. Ran the line down the carpet, under the wiring tube by the passenger trim plate and then up behind the glovebox. Ignore the wires hanging down, those are going to be fed through the center console to the MSPNP. I have 2 circuits of the 6 being used now, one for the Seat Heaters and one for the LC-2. Sometime down the line I would like to install a dash cam, so the circuit is there and just need the wiring. Every bolt is tapped into/through the bracket so if I need to remove anything there is no need for an allen key AND a wrench. All the wiring is with waterproof connectors that have adhesive, shrink wrap with adhesive, and the connectors are also waterproof. The one ground on the downtab is for the relay, which is triggered from the 12v output that the MSPNP provides through the option port. The connectors I added some electrical tape around to give it some sort of strength for the wires that go through it. I am sure it is not needed but it makes me feel better.

My goals were met:

• Hidden fuse box for wiring in additional circuits
• Accessible to read status lights on blown fuses and LC-2 Wideband
• Easily removable to return to stock
• No drilling and using existing features on car
• BONUS: Do not need to remove trim to check status lights

Things I would improve:

• Get a larger tap so the mounting bolts are not so small
• Redesign bracket to sit inside the downtabs
• Make fusebox side flange hole larger so it would be easier to press fuse cover button

All in all it took me a few weeks to get everything done because it is just so dang hot outside. Got started at 4am today and was still sweating at 7am from the humidity.