Rear lighting / fuel sender loom routing

[jagnut66]

Hi,
I don't know if others have had trouble with the wiring to the back of the Morris Minor before but on each of the three I have had there have been issues, that basically stem from the route taken by the wiring harness to the rear of the vehicle.
Namely underneath, with no protection from the elements / salt / sharp objects but the cloth sheathing it comes wrapped in, which soon becomes a sodden oil clogged mess.
Sally, it turns out, is a flasher......
Or she was till I caught her at it................
What I mean by this is that when the brakes were applied all the (side) lights flashed on and off with them, front and rear!
Well it was certainly different........
Not surprisingly, I suspected the oil sodden hacked about and re-jointed mess that was passing itself off as wiring to the rear.
Time for drastic action, in the form of a rear rewire.
However this time I wasn't going to be following the original electrical disaster waiting to happen route under the car, I was going to go through the interior.
But which way, you can't run down the middle because of the (removable) gearbox tunnel cover. If you run them right next to the sills and then have to repair said sills it will get in the way there.
So I opted for the middle road, steering a path clear of pedal depression and utilising some black 'D' shaped self adhesive plastic trunking, which 'hinges open to one side and then snaps nicely closed again.
I now effectively have a new rear loom which, although not original in style (or route!), I know which wire colour feeds what.
I say that because wherever I have connected into the original loom I find that, even if it had a colour code originally, the cloth outer sheathing is now uniformly the same muddy grey colour and when this is removed the plastic coating every wire is black!
So it was a question of powering up and deducing what feeds what.
That said I have enjoyed the challenge and now have brake lights and side lights that work completely separately from each other.
Am I alone or have others had issues with this section of the loom?
Best wishes,
Mike.

[jagnut66]

PS: In case it looks confusing, there were three main wires to the rear, lights (dark green), brakes (red) and a feed for the fuel tank sender (blue).
Additionally I re-routed the wiring for the added rear indicators (Slimmer red and white), so five wires to the back in total.
All earths are black and sourced locally at the rear of the car.
I then ran a lighter green for a feed to the passenger side light and back up to the number plate light (basically I ran out of dark green! ).
I have also converted the Morris boot lid emblem from a dull non-functional reflector to a high level brake light, hence a second red running back up round (following the same route as the number plate light).
Best wishes,
Mike.

[ianmack]

I had problems with my rear light feed and ran a new wire under the car. As you say the harness under there gets pretty horrible but when I pulled off thecloth cover the plastic wires cleaned up quite well with a rag and white spirit. After soldering and insulating the new wire I slid it all into some plastic sleeve and kept the original routing.

The d trunking looks neat but I fear future owners won’t be pleased that you haven’t kept to the colour code if they assume the red wire is for the rear lights.

[myoldjalopy]

The way to deal with those dull reflectors is to bring 'em back up with T-cut.....

[jagnut66]

The d trunking looks neat but I fear future owners won’t be pleased that you haven’t kept to the colour code if they assume the red wire is for the rear lights.

My car, my rules.
Or looked at another way, red for stop and green for go.....
Best wishes,
Mike.

[geoberni]

Whilst I agree having the loom running underneath isn't ideal in terms of it getting dirty, especially for a car that is used regularly in all weathers, I question the need to bring it all inside, especially in the manner in which you have done.

Running a trunking directly across the drivers floor pan?
Haver you got underfelt either side of it, or just carpet over the top, with a ridge across the floor ?
What is it, about 10mm high?
I'm guessing you went for the smallest size that would do the task, so the cables are a fairly snug fit inside.
Looks pretty close to where your heel may sit while driving, plus across the passenger floor in the back.
I'd be far more concerned about cables being damaged by rubbing together under people's feet that I would ever be from a bit of road spray, even with winter gritting.

There is also a technical aspect, which I concede is probably very unlikely given that only the rear lights (apart from the tank sender, but that wattage is probably pretty low) would be powered for long periods, if you were driving at night, but should be considered by anyone embarking on such a project.
The power rating of a cable is not just the thickness of the conductor it's made of, it's also the ability of that conductor to dissipate the heat of the current flowing through it, including the thickness/type of insulation and the conditions of use.
So the loom was previously out in the airflow, but you've now encased it in a conduit, with other cable tightly around it and covered it in carpet. So the heat cannot dissipate so readily. There is the potential (that's not an electrical joke) , however unlikely, that the rear light wiring will now run a little warmer that intended. Add to that any unintentional pressure, from your heel for example, and you could find that in a few 1000 miles of driving, you've abraded the cables together to cause far more damage that you might otherwise had got with them being on the outside of the car.

Far simpler, and safer IMHO, to just get a length of convoluted conduit and cover the loom running along the underside of the car, requiring about 20-30 minutes instead of however long it took you to reroute everything.


I too had considered making the boot reflector into a brake light, but I decided that given most cars with LED type high level lights have between 10-20 LEDs I didn't think that 1-2 was really going to be worth it. Apart from at night, it'll probably just look like a glint in the sun; not really going to get anyone's attention.

[geoberni]

Sally, it turns out, is a flasher......
Or she was till I caught her at it................
What I mean by this is that when the brakes were applied all the (side) lights flashed on and off with them, front and rear!
Well it was certainly different........

Actually, to address the problem that originally sent you on this rewiring adventure, I think it highly unlikely that the cause was your actual loom. When you say

the (side) lights flashed on and off with them

I'm assuming they didn't actually 'flash', they simply went on and off in sync.
Did you actually find any damage where the brake and sidelight wires had shorted together?

In my mind, there's only 2 reasons that would happen, either....
a) a Twin Filament Stop/Tail lamp where the brake filament has broken and dropped onto the side Filament, thus causing the brake supply to feed into the sidelights, or more remotely
b) a poor earth somewhere causing the brakes to find earth as best they can.
This might be if the earth to one or other rear lamp assembly was really poor.

I've seen it so many times where the lamp was at fault, all because the brake filament is shorting to the sidelight filament.

Apologies if this is 'teaching Grandma to suck eggs' as the saying goes, but your post implies that you went straight into the idea that it was the loom, without checking other far more likely things first.

I'd hate this topic to become the benchmark reference for people with similar symptoms to find on the forum and they end up ripping their wiring out for a simple lamp change.

[jagnut66]

The overheating of the wiring will have to wait until I've done a long run to report back on, but being wiring in modern cars is pretty well insulated without issues, I'm not going to panic just yet.
As far as I can tell I don't think I'll have any 'heal on cable' issues, again there this will remain a work in progress until I have run it for a while and I will report back.
To take up your point about conduit under the car, I think this D shaped trunking would work very well in that application, you would just need to decide how to secure it in place.
You would also need a decent (or replacement) rear loom section to make it worth protecting.
As stated, I've had issues with this section of the loom on other Minors I have owned and given how hacked about, jointed, rejointed or just plain bypassed it was already, I considered it passed saving and that it would have been more of a waste of my time trying to do so.
I did check and remake some of the connections in the lamp housings as well but the bulb filaments appear to work fine.
That said I am trialling LED rear bulbs and will see how it goes. I have the originals (and a couple of new spares) if I decide to revert back to standard twin filament bulbs.

Oh, given how much modern drivers like to ride the car in fronts ar*e and that I had one Minor shunted at road junctions no less than THREE times in Milton Keynes, with the excuse always being that 'they couldn't see my brake lights', I'm quite the advocate of a high level brake light of any size.
I did this on my last Series 2 and a lot of people (modern car drivers mainly) commented on it, so it will get noticed.
(And yes, I did point out to those three morons that if they weren't so f***ing close they would have seen them!..... )
Best wishes,
Mike.

[Banned User]

The picture of the loom leaving the engine bay; is that the finished job?

[geoberni]

That said I am trialling LED rear bulbs and will see how it goes. I have the originals (and a couple of new spares) if I decide to revert back to standard twin filament bulbs.

I did say the potential for overheat was, all things considered, only a remote possibility, but the LED lamps will reduce the wattage a lot anyhow, so it's even less likely.

I hope your plan works out for you.

[geoberni]

The picture of the loom leaving the engine bay; is that the finished job?

I think that's the 'before' image.
Mike's 2nd photo shows it running down the floor between the pedals, so I guess it all comes together behind the drivers glovebox area.

[Banned User]

The picture of the loom leaving the engine bay; is that the finished job?

I think that's the 'before' image.
Mike's 2nd photo shows it running down the floor between the pedals, so I guess it all comes together behind the drivers glovebox area.

Phew.

[jagnut66]

Hi,
The first picture shows my new wiring to the rear after it had just been connected into the existing loom.
The reason I haven't replied to the last couple of posts before is that I am mulling over replacing the remainder of the original loom with a new one.
To be fair that loom got me back from East Croydon without issue (apart from the one I discovered above), however it is a bit past its best......
Hence, mulling over buying a new loom or tidying my new wiring in with the existing, after re-positioning the coil, back to it's original position on the bulkhead, something I'll need to do when I fit an alternator anyway.
The other side to my 'mulling' is the fact that a replacement loom isn't cheap, the best price I can find is Bull motif at £174 (inc. VAT).
One thing in a new looms favour though is that it is better than a burnt out Moggy.........
Best wishes,
Mike.

[jagnut66]

Well, here's a bit of work for me to do!
I think I can work out most of it, however any help with colour codes etc would be most welcome.
There is a long piece that I believe is what goes to the rear of the car, another area where the wires exit the sheathing, which I believe is the control box and another near this with greens and whites etc exiting, which I believe is the fuse box. After here I'm assuming it feeds through the bulkhead and on into the instruments and control knobs / ignition key.
What I'm not seeing is any long single wires to feed the trafficators? (I believe they earth through their bodies, if I remember correctly).
I also have a small, separate section of loom, which I don't recognise, pictured below.
As always any information and tips is most welcome and greatfully received.
Best wishes,
Mike.

[Banned User]

This will help with the colours https://www.autoelectricsupplies.co.uk/ ... rder_2.pdf

[jagnut66]

Thanks PoolGuy, I'm printing that off and will laminate it.
Best wishes,
Mike.

[philthehill]

The colours of the wires and what they are connected to/from are listed in the BMC Morris Minor Wksp manual using the relative wiring diagram.

The link above does not reflect the actual wiring of a Morris Minor i.e.

Green / yellow...…….Minor wksp man...…..oil pressure switch

Green / yellow...……...Link above...….……….heater switch.

I would advise that the Morris Minor workshop manual electrical wiring diagram is used at all times for reference and determining what colour(s)/wires goes where.

[mogbob]

Morning ,
If memory serves me right the second picture / woven tape around the loom is the section that goes around the perimeter of the boot lid , clipped to the underside of it.

As others have suggested consult the standard wiring colours of the day from the list and the Morris Minor wiring diagram for your car from the workshop manual.

Lay out the loom , tag all the easy ones first that you can identify. By making steady progress you'll crack 95% of it straight off. The " odd " ones you're left over with will find a home eventually. Once you know the rough position on the loom , you can concentrate on that area in the car ( engine bay nearside / offside , dashboard, interior , boot , outside lights, etc ) what doesn't have an allocated power feed.
Slow and methodical , you'll get there.
Bob

[jagnut66]

Thanks, I'll dig out my workshop manual.
Best wishes,
Mike.

[jagnut66]

Well today has just disappeared!
The workshop manual has proved invaluable and, surprisingly, easy to follow.
Not quite done yet, as long as everything I've done, so far, is correct (and tests with the battery reconnected seem to say yes), then I am left with the headlights, front sidelights and trafficators both of which require work / wiring additional to the loom provided.
I pray for good weather tomorrow.......
The only puzzle, so far, has been one wire, which appears in the section that ends up behind the dash pull switches but which doesn't seem to reappear elsewhere, so I've also no idea where it might end up or what it might be for??.........
It's green with a red stripe....
The only one I can see on the diagram is number 18, which is the left side trafficator wire (the ones which disappear off up the inside of the 'A' pillar and then reappear in the 'B' pillar to feed them) but both of these are separate from the main loom and not provided as part of it......
Which means it can't be that.
Any thoughts?
There's no wiring for a heater in the loom either, which seems a bit remiss of the manufacturers. Not a major issue though, just an earth and a live feed.
Were they still only optional in 1954?
Best wishes,
Mike.