Electrical question - help!

[Ted G]

I started the electrical on my MK4 and could use some help. Other than what is provided, I want to add a few more circuits for certain functions. Here is what I am adding:


Seat Heaters
Footbox fans
Lights for cubby and trunk areas
Radio with no need for the memory wire (bluetooth only)
Reverse light
USB power


I am not using the wiper circuit (10 amp) and could use that for some of this, but that may be too much. Can I use the radio memory wire for part of this? I am also not doing EFI, so thought I might be able to tap into the EFI crank wire. How does everyone add circuits? Do you take one of these and piggyback another fuse box?

Thanks in advance and any feedback is greatly appreciated.

Ted

[NYMike]

We used one of these and tucked it behind the dash to the left of the steering wheel. Can still access it pretty easily with the body on.

https://www.amazon.com/Blue-Sea-Systems-Blade-Block/dp/B000THQ0CQ/ref=mp_s_a_1_7?keywords=boat%2Bfuse%2Bbox&qid=1657161286&sr=8-7&th=1&psc=1

https://thefactoryfiveforum.com/attachment.php?attachmentid=159870&d=1641608979

We added a distribution block for power feed after our battery cutoff so we wouldn’t have a pile of wires running to the post on the starter. I wish I remember whose build thread we got that idea from so I could give them credit, but it was a while ago. Anyway, we pulled power from there and added a relay so the whole auxiliary panel comes on with the accessory circuit.

[Gizmosrcool]

Ditto what NYMike recommends. I have used the Blue Sea Systems in a few other projects and plan to use in my roadster. You can get with or without the NEG. 4, 6, or 12 circuits. I like the 12 circuit split. Gives you two isolated groups of 6 in a single package. I plan to use one group for anything needing always on power and the other group will be switched. I’ll feed it from the battery via a distribution block. The switched group will use a relay. Nice thing each circuit on each group has a fuse.

[BrewCityCobra]

So I planned for many of the same circuits that you discussed above. Below is a picture of a schematic I prepared laying out how to power them (sans radio). Also a picture of the Blue Sea Systems fuse block I used and how I installed it in the drivers footbox.

169070

169071

Like NYMike I installed a secondary fuse panel for anything I wanted to have "constant power". For items I didn't want to have people be able to turn on unless the key was inserted into the ignition I tapped into the corresponding "keyed" power sources - specifically the heater circuit for the heated seats.

Hope that helps.

[Ted G]

Thanks everyone... That helps a lot and I did something very similar on my Jeep

[AC Bill]

Depends if you use relays for the heavier amperage draw item such as the seat heaters and footbox fans, for example. You could use the available 10 amp circuit, as far as power for the dash switches to switch the relays on, but I wouldn't use it as the main source of power for them.
None of the other items mentioned are heavy amperage draw, (unless you get carried away with some powerful back-up lights), so 10 amp should be OK.
You could also just use a simple bus bar, and just fuse the accessories independently.

[Railroad]

Here is an idea on the backup light a fellow builder came up with. Tap into the tag light for power, use a LED light, feed the ground wire through the transmission switch. Your backup light will not work without the parking or driving lights on, but also not needed, if you do not need them on.
I almost did the same, but feed a hot wire from the dash through the same switch and picked up a ground from the car frame.
I also bought a tag frame that has the backup light incorporated into it, so all my wiring routed with the tag light harness.

[phileas_fogg]

The EFI crank (light blue) only has power when you're cranking the engine. Not suitable for your application.

I used the Radio (brown) wire to power my two foot box fans, but you could easily use the wiper circuit. BTW, the Atwood 3" blower fans draw ~7A at start up combined, and ~5A steady state combined. Which means a 10A circuit works just fine.

I used the Electric Choke (tan) wire to power my seat heaters. I didn't measure the current draw on the seat heaters, but I've never blown the 10A fuse even when both seat heaters were on high.

For your cubby & trunk areas, I would put LEDs where ever & tap into the courtesy light circuit to power them.

For the reverse light, as others have said tap into whatever power you want and use the transmission switch.

For the USB, you can use the radio memory circuit. It's ganged with your headlights, so hot at all times.


John

[AC Bill]

Just make sure the wire gauge is adequate for the amperage's.

[toadster]

Just make sure the wire gauge is adequate for the amperage's.

thats sound advice! I have a spool of 14GA wire, overkill for many components! LOL