21 replies to this topic

[Jaybraham]

Good morning all. I've got a birds nest of a wiring loom (much like the majority I'm sure) and even with the best wiring diagrams including the redrawn looms on here I'm hoping to solve a potentially simple question.

What parts of the circuit need to be permanently live and which are best safely putting on a relay switched live?

I plan to move the fuse box inside the car and replace a few badly modified cables (think corroded speaker cable between the solenoid and fuse block) and while I'm working towards those repairs I thought why not future proof the car with a switched live fusebox for things like DLR and Stereo and move my main light switch onto this box also (may have left lights on a few times without realising the don't turn off with the key)

Thanks in advance for your thoughts

[stuart bowes]

hazards are permanent live, as is the courtesy light, for starters 

 

I have replaced (but not actually installed yet) my fusebox with a blade fuse type, with more ways, added some new bits and seperated things out a bit to reduce loadings per fuse

 

other than a few minor changes like adding relays for the lighting I wouldn't do too much in the way of rearranging the loom to be honest - the more you change it, the harder fault finding will be later on and you'll only have your own memory to work from, all the diagrams would be wrong for your car.  which affects anyone you might sell it to as well later on

 

replacing wiring / connectors / dodgy joins though, and getting rid of the d0gsh!t in-line fuse holders, definitely 

Edited by stuart bowes, Yesterday, 10:13 AM.

[Jaybraham]

Yeah I had already thought hazards, interior lights and brake lights being a permanent live just for the safety implications of breaking down or dying mid drive.

I'm considering building a wiring diagram specific to the car as I do it. I have the luxury of working with some highly experienced avionic engineers who can read and draw diagrams like I can live and breathe. Unfortunately though you're right that's its useless later down the line if from one hand to another it's doesn't get passed or gets lost

Thanks for the input however

[mbolt998]

I think horn, brake failure warning light switch, and sidelights are also permanently live. Actually the headlights too IIRC because that's just how it's wired (but you might want to actually leave the sidelights on).

[stuart bowes]

i didn't think brakes were on permanent live, I was thinking that as I typed but seem to recall the wiring to the pedal was green ?  if so maybe switched live same as the reverse light.. or maybe I just remembered wrong lol

 

they probably should be permanent live though agreed, would be a sensible change if not already

 

if you're looking at wiring as well, maybe check if you have the ballasted or 12v ignition and think about if you want to change that

Edited by stuart bowes, Yesterday, 10:14 AM.

[Ethel]

Green is ignition live after a fuse.

 

There's the IVA build manual, or any modern car, to tell you what the legal requirements are.

 

Otherwise the latest wiring diagram for a Mini with the components you want will be a good starting point. A late 80's Metro will be a decent basis too as it'll be largely comparable, with a blade fuse box.

 

Side, tail & hazards make sense. Headlight flasher & horn shouldn't be an issue either as they're momentary. An alternative circuit in case the headlights fail also seems a good idea.

[Bobbins]

Having bought a Caterham nearly 20 years ago that had had the wiring seriously messed with, I discovered fault finding was a complete nightmare the result being a very unreliable car.

It was only after I stripped the loom back and reconfigured it back to standard, correct colour codes and cable routing, correct connectors and all properly crimped, that the car became reliable enough to actually use the way I wanted to, ie. to go places rather than look at it.

Of course you can add extra circuits, relays, accessories, but do it by tagging onto the standard wiring without changing it, eg. use the standard headlamp feed to a relay instead of direct to a headlamp, but make sure it’s clear it’s an add-on.

I hope I’m not telling you how to suck eggs, apologies if I am!

[mbolt998]

i didn't think brakes were on permanent live, I was thinking that as I typed but seem to recall the wiring to the pedal was green ?  if so maybe switched live same as the reverse light.. or maybe I just remembered wrong lol

 

I don't think the actual brake lights are permanent live. But the warning light/switch for when you've got low fluid (or a pressure difference with the older style MC) is always on.

[Jaybraham]

i didn't think brakes were on permanent live, I was thinking that as I typed but seem to recall the wiring to the pedal was green ? if so maybe switched live same as the reverse light.. or maybe I just remembered wrong lol

they probably should be permanent live though agreed, would be a sensible change if not already

if you're looking at wiring as well, maybe check if you have the ballasted or 12v ignition and think about if you want to change that

From the looks of my car there is no ballast cable. Though I'm not sure of there should or shouldn't be, currently everything works okay so I can presume it's all correct for now

Edited by Jaybraham, Yesterday, 03:32 PM.

[Jaybraham]

Having bought a Caterham nearly 20 years ago that had had the wiring seriously messed with, I discovered fault finding was a complete nightmare the result being a very unreliable car.

It was only after I stripped the loom back and reconfigured it back to standard, correct colour codes and cable routing, correct connectors and all properly crimped, that the car became reliable enough to actually use the way I wanted to, ie. to go places rather than look at it.

Of course you can add extra circuits, relays, accessories, but do it by tagging onto the standard wiring without changing it, eg. use the standard headlamp feed to a relay instead of direct to a headlamp, but make sure it’s clear it’s an add-on.

I hope I’m not telling you how to suck eggs, apologies if I am!

I'd rather be told how to suck the egg than bite it out of complacency but appreciate the thought.

The loom has been modified and altered and god knows what has been attempted, as I previously mention it all works but I don't want to do half a job trying to fix some issues and leave others. I've toyed with rebuilding the loom from scratch and marking up everything at each end with heat shrink labels or easy know what and how.

Luckily it's reliable enough and everything works when I ask it to fire up thay I'm not top concerned with the daily use but I am worried about changing anything or making certain discoveries

[Jaybraham]

Having bought a Caterham nearly 20 years ago that had had the wiring seriously messed with, I discovered fault finding was a complete nightmare the result being a very unreliable car.

It was only after I stripped the loom back and reconfigured it back to standard, correct colour codes and cable routing, correct connectors and all properly crimped, that the car became reliable enough to actually use the way I wanted to, ie. to go places rather than look at it.

Of course you can add extra circuits, relays, accessories, but do it by tagging onto the standard wiring without changing it, eg. use the standard headlamp feed to a relay instead of direct to a headlamp, but make sure it’s clear it’s an add-on.

I hope I’m not telling you how to suck eggs, apologies if I am!

I'd rather be told how to suck the egg than bite it out of complacency but appreciate the thought.

The loom has been modified and altered and god knows what has been attempted, as I previously mention it all works but I don't want to do half a job trying to fix some issues and leave others. I've toyed with rebuilding the loom from scratch and marking up everything at each end with heat shrink labels or easy know what and how.

Luckily it's reliable enough and everything works when I ask it to fire up thay I'm not top concerned with the daily use but I am worried about changing anything or making certain discoveries

[Jaybraham]

Slight side note to my original question of what needs to be permanently powered or not, can anyone explain the following wiring set up and how I rectify it so it might do what it should was designed to.

My Ign Coil is a Lucas DBL105
it's plugged to the Distributor with the big black HT lead (I believe)
And negative connection to the Distributor and Tacho (as per wiring diagram) then I have the following
Positive feed in the Coil goes to a fuse and double tapped spade with white Ign Switch cable (is this to power Coil with key turning?)
The fuse these two cables go to, the otherside of the fuse goes down to grill where there is an unplugged spade connector cable tied to the grille. What and where should this cable be connected to technically?

[stuart bowes]

depends what colour it is, black and white is tacho I believe (someone correct me if wrong..)  do you have a rev counter ?

[Jaybraham]

depends what colour it is, black and white is tacho I believe (someone correct me if wrong..) do you have a rev counter ?

Correct and yes I do

[stuart bowes]

but that's not the cable that's hanging free then I assume