S4 dash loom: make or buy?

[JohnCh]

After confirming my slow windows are due to a weak ground coming through the switches, then poking my head under the dash to investigate the rat's nest of wires and view some questionable connections, I'm coming to the conclusion, that a preemptive dash rewire might be the right thing to do. I'm fine making functional improvements during that process — I'm not a stickler for authenticity in areas that can't be seen provided those changes are improvements — but I'm not certain I want to roll my own from scratch and am considering starting with the Autospark dash loom. I've read mixed things about their harnesses, particularly if someone is expecting a plug-and-play solution.

If my goals are to remain faithful to the wire colors present in schematics, and want to introduce changes like relays for the windows, modern LED compatible relay for the flashers, Deutsch connectors to make future removal easier and potentially some other tweaks, is the Autospark a good starting point, or am I better off building something from scratch? The car is a Federal '68 S4 FHC.

I'm not a complete stranger to custom dash harnesses, having recently built a sub loom for my Caterham to integrate a custom dash setup, but to be fair, that was relegated to the switches, gauges, warning lights, and immobilizer. I didn't have to create a loom from scratch, just significantly modify and add on to what came with the car. On the one hand I love a challenge and learning something new, but on the other, I'm inherently lazy and like instant gratification Advice welcome.

Thanks,
John

[The Veg]

A few years ago when I had my Plus 2's dashboard out I addressed some of these issues. I found that while the dash-harness was in generally good condition, I did put new terminals on all the wires as the original ones seemed quite oxidised. A lot of the bullet-connectors were so stuck from oxidation or corrosion or something that they could not be separated. I replaced them a ll with a pair of 15-pin Molex plugs to make future removals and installs easier. One plug was full and the other used all but 3 or 4 pins. The two plugs were oriented in opposite directions to make cross-connection impossible.

As for the window earths, I ran new heavy-gauge earths straight from the motors to the chassis-bolts on the tunnel and that made the windows move with authority after all other fixes failed to make a difference.

[JohnCh]

Thanks. In addition to corrosion on the terminals, I'm concerned that after 56 years, the insulation is reaching terminal brittleness.

Interesting about the +2 windows. It sounds like they operate differently than the Elan which has two wires to the motor plus a ground to the body for radio noise suppression. The switch flips which wire receives positive and which receives ground to control motor direction, so a dedicated ground to the motor won't work. I need to address a solid ground at the switches, which appears to require dash removal, And as long as I'm in there....

[The Veg]

Thanks. In addition to corrosion on the terminals, I'm concerned that after 56 years, the insulation is reaching terminal brittleness.

Interesting about the +2 windows. It sounds like they operate differently than the Elan which has two wires to the motor plus a ground to the body for radio noise suppression. The switch flips which wire receives positive and which receives ground to control motor direction, so a dedicated ground to the motor won't work. I need to address a solid ground at the switches, which appears to require dash removal, And as long as I'm in there....

Good point, I'd forgotten that the Plus 2 does use different bits including a GM motor- same one you'd find in a '70 Chevelle, believe it or not- and yeah, dedicated earth through the motor's chassis (in the Lotus, earth-wire to one of the mounting bolts) and the switch sends the +12V through either of the two wires that connect to it.

But the point remains, both the + and the - need a good free-flowing connection for the motor to work strongly. Even putting relays for direct battery-power on the +12 wiring didn't make a difference with mine until the earths were improved. So I guess if your window-earths have to go through the switch, then from that point run them as directly as possible to the chassis.

[Andy8421]

John,

As soon as you go down the non-standard route, the argument for starting with a standard loom becomes weaker - particularly if you aren't concerned about wiring colours and want to change connectors.

If standard colours do matter, then using a standard loom as a starting point avoids having to buy short lengths of wire in specific thicknesses and colour combinations that may prove difficult to source.

Andy.

[StressCraxx]

I vote to buy, then modify/add relays to suit your purposes. It will be easier for the next owner.

One caveat. I obtained a complete new harness during the rebuild of my S3 Elan. As I started going through the connectors for the tail lights, I discovered two wires in the harness had pulled out from the bullet connectors. I also looked at the wires coming from the tail lights. The bullet connectors at the tail lights were crimped at the bare wires and also crimped at the insulation end as well. I looked over the entire harness and discovered NONE of the bullet connectors were crimped on the insulation! So before I can install the new harness I need to finish crimping the connectors on the wire insulation.

[RichardHawkins]

John,

I was horrified by the old wiring on 1968 S4 fixed head, and decided to do my own thing. I think bullet connectors are awful. My approach was a bit different, I decided on a donor car that had the distribution board by the passengers knees, in my case a Skoda Felicia (part of the VW group). This vehicle has 8relays and 22 fuses, and at the time 10 year old cars were scrap value. I carefully dismantled the Felicia removing and labelling all the wires, I found a Haynes Manual very useful for the wiring diagrams. I sold the old Felicia to the scrap man who came and collected it.

The Felicia provided enough wire and connectors to nearly do the job. I have used some Deutsch connectors in the front of the car as I didn’t have enough of the connectors used in the Felicia and could not find a supplier until after I had finished!

My electrical knowledge is rudimentary, so using a donor car solved problems such as relay types and wire sizes. I made a serious error, I routed the wires when the heater was not installed, and then found the heater clashed with most of the wires behind the dash. I then had to buy new wire as the Felicia did not provide enough to correct my error, this error also took a long time to correct, as the wiring had been complete.

The work took about a year and correcting my error probably another 6months. I do have a much better system using better connectors and gained a perverse satisfaction from the achievement.

Was it worth doing? I am not sure, with the knowledge I now have if I had to start again I think I would still do it and hopefully much quicker.

Hope this helps,

Richard Hawkins

[JohnCh]

Thanks everyone for the responses. I spent a lot of time in the garage today reading through old posts on this topic and digging a little more into the car. The first discovery is that my headlights no longer pop up. I checked them when I bought the car six years ago but haven't tried them since. My second discovery is that the headlights work just fine with the pods closed. From what I've read, they shouldn't. Between that and looking at the wiring in the nose, realized it's not just the dash loom that needs attention. I think I may be on the brink of scope creep.

StressCraxx, I assume that's the Autospark harness? Where did you buy it? I suppose if I am modifying it, then those type of quality control issues aren't as big a deal, but it still doesn't instill confidence.

Richard, I'm not sure I want to go that far down the modification path, but I do like the idea of modern car conveniences like more than two fuses for the entire electrical system.

[Andy8421]

John,

The wiring on the Elan was poor when it came out of the factory. Based on standard Lucas practice of the time, apparently little thought was given to the implications of a lack of earth return through the body, and the flammability of the car.

If your wiring is original, I would strongly recommend replacing it all. In particular, the combination of heat and water in the engine bay and nosecone mean the insulation on the wire will have gone hard and cracked, the wire itself will be corroded and connectors (which were never water resistant) rusted and failing. Enthusiastic DIY owners often hack the wiring around, and what is left after all this will give you years of trouble chasing elusive earthing problems up and down the car.

The headlamps were designed to switch on when raised if the headlamp switch was in the on position, or flash if raised when the switch was set to off. Two repurposed interior light door switches are fitted to the headlights to detect the movement. These cheap and nasty switches (optimistically called 'microswitches' in the manual) were originally designed to be protected by fitting in the door pillar of a car. In their Lotus application they are open to the elements, get wet, and fail. Many owners fed up with unreliable headlights disable this aspect of the wiring so that the headlamps always come on with the headlamp switch irrespective of headlamp position. It is likely that this has been done to your car.

Good luck.

[RAJ2628]

My harness was in a dreadful condition when I bough the car, so I bought the full 3 part harness for my S4 from Autosparks. I am not an electrician by any means, so I had lots of questions. Autosparks were really helpful. My harness did not include a branch to connect to the registration plate light. They made one up for me without any fuss.
My observations were that the cable junction areas were a bit bulky, particularly behind the dash making it really awkward to fit. The ignition switch has little room between the dash and heater box, so the wiring is really cramped in that area. The whole harness needs a bit of slack in the engine bay to allow a neater route to be found. The branch to the dynamo/alternator could do with being a few inches longer. I also found half a dozen or so loose bullet connectors, so it is important to check on delivery.

[smo17003]

My harness was in a dreadful condition when I bough the car, so I bought the full 3 part harness for my S4 from Autosparks. I am not an electrician by any means, so I had lots of questions. Autosparks were really helpful. My harness did not include a branch to connect to the registration plate light. They made one up for me without any fuss.
My observations were that the cable junction areas were a bit bulky, particularly behind the dash making it really awkward to fit. The ignition switch has little room between the dash and heater box, so the wiring is really cramped in that area. The whole harness needs a bit of slack in the engine bay to allow a neater route to be found. The branch to the dynamo/alternator could do with being a few inches longer. I also found half a dozen or so loose bullet connectors, so it is important to check on delivery.

This mirrors exactly the problems that I also had with the Autosparks S4 harness. Mine was new/unused via Ebay, so I couldn't really expect any help from them. I have checked their website and they do offer a bespoke harness option. If I was doing another I would ask if they could supply a harness using more modern thinwall cable (see here for a thinwall discussion viewtopic.php?f=38&t=50234). Alternatively, having already done one car, I would consider making my own, there are a few "modified" wiring diagrams on here that have been devised by members to include better fusing etc. than the original.

[RichardHawkins]

John,

I did not mention headlights, maybe I should have, I converted to Mazda MX5 (I think it is called a Miata in the USA)
headlight retractor motors. One of the other things I learned from Skoda Felicia was their method of earth return was something I had not come across before. There are two or three (I can’t remember the number) earth return studs welded into the body structure in dry locations. All items that require an earth return ie lights have the earth return routed to one of these studs. When dismantling this old scrap Felicia I did not find any corroded or dodgy connections. As I missed the opportunity to weld studs to my chassis I installed a separate earth return system, rather like an earth ring main. Skoda use thin wall PVC insulated cables, I found no damage.

As for mission creep, I suffer from technical arrogance, thinking I can make an improvement and maybe I do, but it always takes ages.

Hope this helps

[JohnCh]

As for mission creep, I suffer from technical arrogance, thinking I can make an improvement and maybe I do, but it always takes ages.

Then you'd appreciate what I did to a perfectly good Caterham 420R

I sent Autosparks an email this morning inquiring about building a custom loom from thin wall wire. I'll report back their response. If they can do it and the price is reasonable, I may have them alter some wire lengths based on feedback received thus far.

The dash is now ready to tilt forward far enough to examine the harness. It looks like the only things left are removing the bonnet release cable and disconnecting the choke, which I'll deal with in the morning. I did find more creative wiring back there and have developed a healthy respect for anyone who is competent at quickly disconnecting bullet connectors.

[stugilmour]

I sent Autosparks an email this morning inquiring about building a custom loom from thin wall wire. I'll report back their response. If they can do it and the price is reasonable, I may have them alter some wire lengths based on feedback received thus far.

That is what I was initially thinking John. Have you seen Autosparks web pages for a generic kit car loom, which I would think would be a great starting point. Unfortunately they don’t indicate what wire colour standard, if any, they use. Ideally it would broadly follow the usual British standard.

https://www.autosparks.co.uk/deluxe-fro ... ng-harness

In any case, the basic loom layout appears to allow for mounting the relay and fuse block within the glove box. More relays can be added in the same location. Also appears to have a couple of large connector blocks that hopefully allow disconnection of the dash with the main power blocks, switch gear, instruments, etc for any service. The rest of the runs appear to be “fly lead” style with no connectors installed.

That is the route I took when I rewired my Plus 2 using a similar generic kit car loom as a starting point. Mine was supplied by Spyder, but I don’t know if they still have them or something similar for their Zetec’s. Needed quite a bit of modification but worked out.

The specific adds I see as questions for Autospark on this loom is emergency flashers/turn signals, alternator setup details.

You will have to add the window lifts, interior lights, light pod motors and a few other things, but this is relatively easy particularly if they use non-adhesive loom tape, or just use flexible wire covering to add another run. Thin wall is easily sourced in all the custom colours you will need.

As an alternative source of kit car looms, I see Holden and Stafford Vehicle Products have something available, but the wire colours might vary from standard a bit.

Another starting loom source might be Advance Auto Wire. Just came across this US based supplier today when looking around for you. Amazingly on their enquiry page they indicate they have a version for the Lotus Elan! They seem to largely use British standard wire colours off of the power block. There diagrams and documentation looks first rate. I would definitely consider these guys as a starting point.

http://www.advanceautowire.com/

The Triumph and MG guys seem to be complementary. Here is a picture of an MGB version coming out of the box. This fly lead style allows you to move the several front and rear wire runs around a bit to suit, and even cut and easily add dash block connectors. I used plastic loom covers for most of mine, only loom tape were runs branch off. All the block connectors are easily added once the loom is installed in the body. Standard connector blocks for things like halogen headlights, Lucas wiper motor, NipponDenso alternator, etc are available online with a bit of searching. Other connectors for sidelights etc with pigtail connections are just generic blocks rather than bullets.

Adding wires is a piece of cake at this stage. I don’t see specific black ground runs in the loom (easily added now, might be included in an Elan version?). My loom had the ground runs included as it was billed for a fibreglass kit car. I opted to add to a ground bus at the right dash bolt grounding point; not sure of details for an Elan. Only other ground points are engine mount straps and the rear battery; with the Plus 2 this is typically moved to the right side tower body bolt to be completely out of the weather.

Top Tip. I would only include the stock functions within my loom runs, and consider adding another separately sheathed run for ‘custom’ functions like pod lift motors, aftermarket ignition, accessories, O2 sensor, fuel injection, etc. that by their nature use wire colours to a different standard. This really helps keep the standard and non-standard colours straight. If I had it to do over again I would consider using different coloured sheathing, like grey for custom, black for stock sort of thing. I would include technically non-stock but sorta generic upgrades (electric fuel pump, upgraded tach wiring, electronic ignition power supply) within my loom and use British Standard colours as required.

When documenting your work, go the extra mile and document all the pin and wire colours in your multi connector blocks. In actual fact, this is where you will concentrate any post installation troubleshooting or repairs. Can be surprisingly hard to see the colours in the car.

I just documented each circuit separately on 11 x17 cardstock. With the Advance Auto Wire as a starting point this would be limited to the stuff you change or add which is a huge leg up. Definitely include the block connectors in these diagrams.

No direct experience with this product but I really like what I see in it. Relays and fusing looks adequate for basic stock functions. If adding relays for say window lifts or pod motors this would be a separate relay block. Mounting relays on the dash saves tons of grief with the wiring because only the main conductors to the device leave the dashboard. Note you might need several relays for pod motor control, getting the existing simple dash switch to work with the different hazard relay circuit, sidelights depending on your exact model, etc.

Great winter project by the way. With the dash out and laying on a carpeted floor the entire power block and loom can be pre-tested before running through the firewall and rear bulkhead and adding connectors,, which is a huge factor for ease of installation.

HTH. Interesting topic. Keep us updated no matter how you decide to tackle the wiring.

[JonB]

I did find more creative wiring back there and have developed a healthy respect for anyone who is competent at quickly disconnecting bullet connectors.

I found on my 54 year old bullet connectors that spraying the female joiners with a bit of WD40 helps. When pulling the big bundle apart (behind the glovebox), only two of the bullets broke off. The others all look good, if a little dull. I used needle nosed pliers so as to grip each wire firmly, as close to the bullet as possible. I reckon if I replace all the joining parts (female-female connectors) and clean the bullets, I should get a good result. (Full disclosure: my loom is 100% original and untouched since it left the factory. Even has the anti-theft switch, which has fallen apart.)