Adding extra wires for future proofing electrical upgrades…

e9Leveque

e9Leveque

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Since I pulled my wiring harness from the front of the car into the engine bay in preparation for refresh of bay, I’m wondering about adding some extra wires that go to the fusebox area or beyond for any future upgrades I might do. I already have my battery in the trunk with a distribution block in the old battery location, and have added relays (and their wiring) for stereo/amp, headlights, and rear window motors, etc, but wondering what other upgrades people have done that might be more easily accomplished with wiring already in place rather than having to go add an additional wire to the harness later.
Some options I’ve seen discussed in searching older threads:
1. Heated seats. I added this to my E39 and it’s a game changer for colder days (or even cool spring days) here in Seattle. That was easy, but these seats seem a bit daunting to me and I’m not sure whether it’s worth taking on. This would likely be a wire that I could add just terminating with extra cabling under the driver seat.
2. Map light: my car doesn’t have this, not something I think I would need/want, but it does look like an option on some cars
3. A/C: while I imagine most of this wiring would be within the engine bay, this is an upgrade I’ve considered having our good friend Don do in the future. Any wiring for the controls that should be added now?

Any others? Hopefully this list will serve as a list of possible electrical upgrades for others as well.
 
one map light ideas is to use the e28 / e30 mirror with map lights at the bottom edge. you just have to run power from the dome light to the mirror (a few inches for non-sunroof cars).

i like the heated seat idea, to me its only something to tackle if you reupholster the seats.

i added a power distribution block in the interior of the car, fed directly from the battery to send power to the window motors and anything i do with stereo or possibly heated seats. i think i ran a 10 or 12 gauge wire down the harness.
 
AC wiring:
in the front you have
-the additional fan (which has a direct + from the battery to the relay)
-the pressure switch in the drier
-the compressor

the other wiring is from fuse box to the center console - blower motor, blower switch and temp switch.

There is one wire going from the temp switch to the engine bay.
 
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Dlc said:
AC wiring:
in the front you have
-the additional fan (which has a direct + from the battery to the relay)
-the pressure switch in the drier
-the compressor

the other wiring is from fuse box to the center console - blower switch and temp switch.

There is one wire going from the temp switch to the engine bay.
Click to expand...
Got it - so worth having one heading to rear of console for that.
 
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in the wiring diagram you have
-12 battery
-11 fuse
-10 add'l fan
-9 relay
-8 compressor

in the front

3-7 sit in den center console

1771968511286.png
 
I've installed a couple of additional circuits into my car:

- Seat harness inertial reel (my harnesses contain an inertial reel that will pull you back into the seat when the yaw sensors detect an accident).
- Fuel pump controller for my electric fuel pump.
- Footwell lights on a fade to black timer (this is actually an add-on to the dome light circuit).
- Secondary temperature trigger for the fan in front of the condensor, run off a temp sensor in the lower radiator hose connection independent of whether the a/c is on.

You might also consider a fog light circuit, and a circuit to charge your cell phone.
 
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You don’t need an extra wire in the console for the a/c. If adding a USB like I did in the glovebox don’t run it off the same fuse as the radio.
 
HB Chris said:
You don’t need an extra wire in the console for the a/c. If adding a USB like I did in the glovebox don’t run it off the same fuse as the radio.
Click to expand...
My radio has a USB output off the back of it (Retrosound) but yes, maybe best to just have a separate dedicated circuit. The distribution block I have in the engine bay has a fusebox so I can run things “direct” from battery (which all go through a much larger 100A safety fuse) or I can have items run from block to fuse/relay and then out to rest of car
 
You might want to run a few 00 wires from the trunk to the engine bay for that future Mr. Fusion electric power source :p
 
e9Leveque said:
Touché ! May have to print this as a lark at some point. I also still owe you an assessment of the LED rheostat that we had discussed in the gauge lighting thread. The part arrived but I haven’t had time yet to play with the multimeter.
Click to expand...
Only if you promise to get a photo of it mounted to the trunk lid of your coupe!!
 
Swinging back through this thread given some of the recent discussions on wiring when considering add-ons like kill switch, etc. I'm in the midst of wiring in my additional gauges so this is front-of-mind for me. When considering the various ways additional wiring can be added, what are the general thoughts on following options. I'm new to this so would rely on those of you who have done this in the past.

1. Wiring direct to battery, either by the octopus wiring on top of the battery terminal or by adding a distribution block nearby.
Advantage: Easy.
Disadvantage(s): May start to get a bit messy, and these circuits are always-on, so unless they are used to power triggered relays or low-draw items there is a chance for battery drain

2. Adding an "add-a-fuse" to the fusebox. This device has a fuse-shape bottom so that it plugs directly into a modern-style fusebox and then has the capability to place the original fuse in place with anywhere from 1-5 additional fused outputs that are butt-connected onto new wiring
Advantage: Still pretty easy and somewhat "clean" since it's contained in the fusebox area. Doesn't involve defacing or cutting any existing wiring. Allows for choice of ignition-switched or always-on circuits easily
Disadvantage: requires owner has updated fusebox to modern style rather than original torpedo. Makes a somewhat cramped area a bit more cramped. Has the potential to overload the primary circuit chosen, although that entire circuit is fuse-protected.

3. Tapping into existing wiring somewhere along its length. While this isn't ideal, I'm not sure how you get around this for particular situations. The kill switch by necessity involves breaking an existing circuit. Likewise if I want to wire my gauge lights to come on with the dash illumination then I need to tap into the wire exiting the light switch on its way to the dash lights. So, if that's what one needs to do, here are the options - would love to know thoughts
A. Cut the wire and use a crimped "wire nut" to join the two cut ends and one or more additional wires. Easy, but needs some laxity in the original wire since cutting it, stripping each end and then bringing all of that together effectively shortens the wire. Hard to undo easily also.
B., Use one of those plastic taps that has one half which clamps onto the donor wire and pierces through its insulation to the copper inside. The other half is attached as a spade connector to one end of your new wire. Relatively straightforward but I've found those things hard to place. It's nice that it's easy to separate the new circuit if needed, however, leaving behind only the tap on the donor wire
C. Use wago connectors, which can accept one wire in and have multiple wires out. Each feeds into its slot and then has a lever which clamps down and holds the wire. Probably the easiest of any of the above, easy to undo, but I wonder whether these things will shake loose with vibration over time.

4. If ignition-switched power is needed I suppose you could do an alternate of version 1 and have the ignition switch be the trigger for a relay that supplies power directly from the battery to the added device. This is just an alternate of what many of us have done with the window motor switches or headlights, where here the ignition switch is just that trigger. If adding multiple circuits, however, it still seems that you run into the same problem - you need to tap into ignition somewhere and you for each new relay you need some way to get that ignition trigger signal.

In my research online it appears that any and all of these have been recommended. Soldering seems to be the universal "not a good idea" but beyond that...
 
Have you considered touch safe terminal blocks? They are more secure than the Wago connectors IMHO. They are configurable for size, mountable, and there is a DIN version that can mount to a rail if you want to have several.
Here's the page on McMaster.com. There are other suppliers online as well.Touch safe connectors McMaster.png
 
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Hmm I hadn’t seen those. I’ll take a look - there’s an old-school electronics craft shop near me that would stock stuff like this. For my current purpose mountable isn’t as applicable but good to know that’s an option as well.
 
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