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Making my own main loom/harness


monkie

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Wiring up for the ignition switch - I'm feeling daft for not taking a photo, I thought I had but there you go whats done is done!

I know (or think I know) the following on the ignition switch:

  1. Brown/red to number 1 glowplug
  2. Brown supply from the postivie bus
  3. White (ignition on) supply to circuits
  4. White/red to starter solenoid
  5. This is where I'm confused. The circuit diagram says another white feed. I think it is white/orange for the heater blower motor (and radio if fitted). I have seen other posts on here that suggest white/black.

Can anyone please confirm that for a 1988 110 it is a white/orange wire? White/black makes no sense to me as that is for the heated rear window to my knowledge and I wouldn't be wiring that up directly to the ignition switch. Ignition on live would make sense to me for the heater blower/radio supply.

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I think I might have answered my own question. Position 5 has the positive feed, 2 has the brown/red for glow plugs. 1 and 3 become live with the ignition on so they will be for the white and the white/orange leaving position 4 for the white/red to starter relay as it becomes live when I turn the key to the start position. 

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Thick brown/red not used on Tdi engined vehicles, that wire is redundant, 

White/orange is a 12v feed ign switched for air condition system when fitted. 

This old post of mine may help with ign switch connections

 

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Thanks Ralph, that's the thread that caused me some confusion. Having a closer look my ignition switch is slightly different to the one in that drawing. On mine position 5 is the main feed and 2 is energised when the key is held in the pre-heat position.

The white/orange circuit as I understand feeds some auxiallary items such as AC where fitted, radio and the blower motor. For the blower motor specifically working backwards - the fused feed is purple/green which is fed via the fuse from the white orange wire to the ignition switch. That makes sense to me. The white/black circuit in the other thread confused me as I understand white/black to be the feed from the relay for the heated rear window which is powered by the brown permanent live via the voltage sensitive switch - nothing to do with the ignition switch.

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Quick update. The loom is ready to be fitted. Can't wait to drive my 110 again. Fingers crossed it all works! 

Big improvement on the fuse box wiring. A nice thick earth to each corner that will all link up to a bus bar in the battery box. 

Improved connectors for all switches and lights etc. 

 

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IMG_20210304_173313.jpg

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Putting the dash back together I stumbled across a realisation by accident with respect to the ignition switch. I got the white and the white/orange wires back to front on the ignition switch. The engine would crank and not fire up. With the ignition on I checked the stop solenoid, it worked. So I took an injector pipe off number 1 injector and cranked it over. Nothing. 

Then it hit me, the feed to the circuits to the white wire must be isolated when cranking. Yes it was. I switched the white wire with the white orange and it fired up straight away. This makes sense as the radio, blower motor, AC if fitted run off the white/orange and you don't need those running when cranking the engine over. 

So on my ignition switch which is standard for a TD 110 of the 1980s... 

Terminal 5 is the live feed with the brown wire from the positive battery terminal via the bus on the starter solenoid. 

Terminal 2 is live when the key is held in position 2 for the glow plugs using the brown/red wire. 

Terminal 4 is live only when the key is held in position 3 so is used to energise the starter relay on the white/red wire. 

Terminal 3 is live with the key in position 1, 2 and 3 so is for the ignition on circuits for critical things like powering the engine loom via the white wire. So the white wire must be connected to this one for power to circuits in positions 1, 2 and 3.

Terminal 1 is live only with the key in position 1 so is to feed circuits with the key in position 1 only and not when energising the glow plugs or cranking. The white orange wire is connected to this one. I accidentally had the white wire connected to this terminal which is why the stop solenoid switch off when cranking preventing the engine from starting. 

Reflecting on it, this numbering system makes sense in relation to what is live when the key is in a given position bit easily overlooked. 

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I drew a little diagram of the ignition switch wiring to help if anyone gets a bit muddled up in the future. There are no white/black wires to my switch which is I why I got confused. I also learnt to my detriment that just becuase something is live with the key in the on position dosen't mean you can plug what wire you want to it!

Hope this helps people:

 

Ignition Switch wiring.png

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Good work Monkie, something I will have to tackle on my build at some point. Did you just use your old looms to get the lengths for each section? Mine is a 98 110, But Im thinking of running the TD5 led warning light set up and digital speedo signal.

And thanks to those that added the links to the Factory wiring diagrams.  

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Yes, I broke the old loom down into individual circuits and just replicated them one by one to build up the new loom. I used a board to help me do it as others in this thread suggested. 

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  • 3 weeks later...
  • 4 weeks later...

A few months on after the rewire, I am happy that all is working well and reliably but for anyone reading this thinking of doing a complete rewire I want to be open and honest with a few things of doing it in standard form... What have I discovered along the way and what would I do differently knowing what I know now? 

A huge positive is I feel I have a far better understanding of the electrical system on my 110 and better placed to find faults in the future. The biggest thing however is I fear I might have missed an opportunity to customise things better. Think very carefully about this statement if you are considering a rewire yourself. 

I rewired pretty much as standard, following the same wiring colour codes as original. I did build in a few small modifications such as relays to the dipped/undipped head lights and modern connectors. 

On the connector front, I like econoseal but I'm not as fond of the superseal. I also think some connectors on the original loom are unnecessary potential points of failure as some have pointed out in this thread @Sigi_H at time I didn't agree but I have come round to this way of thinking now. I would certainly eliminate the connections to the engine loom and the rear loom if I did this again. Even to the lights, thinking if I needed to remove them I could then cut the wires and add in a connector at that point. 

The biggest thing I have since discovered are hand held label printers that actually print on heat shrink allowing you to permanently label individual wires - wow, game changer! Had I have known this from the start I think I would have just bought big reels of cable of just a few solid colours say 4 or 5 and then labelled each individual wire at both ends rather than learning (and forgetting) what green with a black trace means etc... I also think I should have given more thought to fuses. 

I'm not happy with the amount of unfused lives in the standard wiring. This I am going to address and not leave as standard. I want to eliminate all unfused lives in the loom. The obvious place to start is the glow plug feed, but I also want to fuse the main supply to the ignition switch. I'm thinking one off the shelf method to do this is to fit a maxi/midi fuse box somewhere on the bulkhead or in the battery box for this job. 

I'm just looking for some advice from those that have done this before. Is this a sensible idea? Anyone done this a better way? What size fuses should I be looking at for the feed to the ignition switch? 

The feed to the starter motor is also unfused. Is this a silly idea? Has anyone put a fuse to the starter motor? If so what size? 

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Your ignition switch is the same as mine (1989 110CSW) so don't know why your wiring is different my terminal 1 used to be brown/ red feed for the old 19J glowplugs, this is not used anymore on the 200tdi, as the glowplugs take their feed from a different place straight off the battery, then the timer passes it to glowplugs when energised. 

Pleased to see it all works & your mobile again. 

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The only explaination I could offer for differences between the two ignition switches are none standard replacements made by various different owners between now and when it left the factory. The numbering I used on my diagram was taken from the back of the switch. 

Have you fused your glow plug feed Ralph? 

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Yes that could be the reason, AFAIK my ign switch has never been replaced since I've owned the 110, 

my ign switch is 35288 middle right of  diagram below

post-20-1210699152_thumb.jpg

No my glowplug wiring is factory standard as per the conversion install booklet that came with the engine.

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I fused mine when I fitted the glow plug wiring monkie, I used a HD strip fuse and holder mounted on the bulkhead in the feed to the relay.

As for wiring, I considered new harnesses and I considered making new but in the end opted to use TD5 wiring from breakers as I'm lazy and tight 😉. This has proved very reliable over the last 10 years or so.

HTH

Mo

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  • 2 weeks later...
On 4/25/2021 at 12:09 AM, monkie said:

The feed to the starter motor is also unfused. Is this a silly idea? Has anyone put a fuse to the starter motor? If so what size?

That's normal. None of my newer vehicles are fused either, that is the heavy gauge from the battery to the starter I assume.

I was cheap and used the labels and 8 colors, as well running a stripe down some with a sharpie cuts down on costs. I'm glad it worked out well for you. Good job.

 

Sean

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Ive gone down a rabbit hole now (seems to be a Land rover thing!) 

I've got myself a maxi/midi fuse box and the Bussmann fuse and relay box from @SteveG. I am going to run run a feed from the bus on the starter (removing all others) to the maxi/midi fuse box to delete all the unfused circuits from the original loom. 

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Good follow-up, a few observations from my own experience;

I bought a fairly expensive label printer that prints on heat-shrink and it turned out to be 5h1te, kept jamming up and the labels were very expensive - also a lot of those things do NOT actually last on contact with mud, water, or even UV light so although it can sound like a good idea it can actually leave you worse off in 5-10 years time when none of the labels are readable anymore.

Following the factory wiring for factory items like the standard lights is a good thing - going totally custom / different colours etc. can seem like an improvement now but again - 5 to 10 years down the line you've got to remember what you did rather than just "it's the same as factory". By all means uprate stuff or eliminate unreliable connectors etc. but sticking to factory colours & basic scheme is a good thing.

Unfused lives - yes, hate them, have removed all of them bar the starter & alternator for obvious reasons.

I put a midi fuse in the battery box on the feed to the main box and then a 4-way bussed midi-fuse box to break out the separate feeds (one to main fuses, two to engine fans).

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That's interesting to read about the labels on heatshrink. I got a Brother E something or other and the genuine heatshrink tape casset. So far I have used it on the wires to my gauges that are right next to the hot oily engine so I'll see how they take the abuse. 

The experience I have gained so far on this rewire project is that if anyone wants to do just one thingand is on a tight budget to improve the electrics on their vehicle: I would say run a nice thick earth wire of say 35 amp capacity to each corner that go straight to the clamp on the battery negative terminal. Most of my budget was spent on connectors and I'm hindsight you can eliminate almost all of them in my opinion. 

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2 minutes ago, monkie said:

Most of my budget was spent on connectors and I'm hindsight you can eliminate almost all of them in my opinion. 

Depends on the car IMO. I'm planning on running as much of the loom(s) as possible inside the car and making all the sections of loom removable. With decent sealed connectors it won't have any issues. 

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