Series 1 3.8 Wiring Modifications, Headlamp Relays etc

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rfs1957
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#1 Series 1 3.8 Wiring Modifications, Headlamp Relays etc

Post by rfs1957 » Mon Jan 06, 2014 1:31 pm

Having started to explore ways of fitting period-looking relays to carry the headlamp currents, and fit them somewhere that was both accessible and warm/dry, I soon discovered that the wiring-harness (brand-new 25 years ago and only 7.000 miles since) had been chafing on the tubing near the LH top wishbone.

The big fat red-yellow wire was the only one to have been actually damaged, though it was through to the copper, it runs from the 4th position on the light-switch, destined to run fog-lamps I don't have, but - since it has no fused protection whatsoever - it would have fritzed the whole harness if I had ever turned the switch as far as position #4.

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I realised that, in the same way, the brown wires from the battery (via the starter solenoid terminal) end up doing all their work behind the centre console with no fused protection either.

How many of us, I wonder, realise that all the white wiring under the dash is live yet unfused, and that includes the ignition/coil feed ?

This post, then, shows some of the modifications I ended up making to address what seemed like quite serious shortcomings, whilst keeping almost everything out of sight, using period-looking additions, and using existing wires within the harness where possible so as not to clutter the engine-bay up with additions. I inherited from the PO a car that feels/looks pretty close to the real thing, thanks to the endless lengths he went to get the right original parts, so I feel obliged to avoid obvious or incongruous additions as far as possible.

I source my wiring ingredients from both Vehicle Wiring Products and Auto Electric Supplies ; they are both very good but on balance I think AES are better for period stuff, their web-ordering format is excellent, and details like the clear/soft shrouds for Lucar connectors are better from them.

http://www.vehicle-wiring-products.eu

http://www.autoelectricsupplies.co.uk

Suffering from man-forgetfulness I also kept track - for once - of what mods I did by opening the original wiring diagram in "Paint" software (which I think all PC users have whether we like it or not ?)and updating it using the various functions like copy/cut/paste etc so as to obtain my own "period" wiring diagram, which some future owner or my children may one day appreciate.

I have put a downloadable version here following requests from other Forum users : mine prints better by opening it with Paint first and giving the print command from there.

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Cleaning up the wiring diagram

The first thing I did was to clean up and simplify the wiring diagram using "Paint" to suit the RB340 voltage-regulator and the 4-way lighting switch that are fitted to mine, since most 3.8 diagrams show several options on the same drawing, which I found impossible to follow.

The modifications are resumed here, see the grey-blue zones :

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Bus-Bar and Fuses for general protection

Fusing the feeds to the new headlamp relays was going to need 2 new fuses, so I went for a Lucas 7FJ 4-way fuse box (genuine original easily found on Ebay) and resolved to pass both of the non-fused brown main-feeds to the dash through the other two ; the best place (neat, discrete, accessible) to mount this seemed to be right on the solenoid terminal, by making a sort of bus-bar out of brass and riveting it behind the fuse junctions in place of the original spades.

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In this way the feed to the fuses is as direct as possible, one fuse (35A)protecting the brown that goes to the ammeter, the second (10A) the brown that feeds the fuses ( N°3 and N°8 ) that don't go through the ammeter, neither of the standard brown cables or their terminals needing any modification, the third and fourth fuses (35A) being the main and dip relay feeds.

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Initially I had run it for a couple of hundred km of testing with a jury-rigged bus-bar-cable, followed this with a mock-up out of thin zinc, then made the definitive version out of 15/10 brass sheet - trying to get the angle right so that the fuse-box sat square in relation to the battery and the rest of the car.

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The ammeter feed needs a 3/8" flat spade riveting in place of the 1/4", although it would have been easier and probably better to just use 2BA brass screws throughout instead of rivets ??.. but I got shipwrights' disease.

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The modifications are resumed here, see green zones :

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Better Bonnet Earth

Given that the earth connections run as largely invisible wires within the harness, I decided to belt-and-braces the earth to the bonnet by using the famous damaged red-yellow wire as an extra earth, whose routing I understood and could follow, and got a good earth-post into the front chassis-tubes via the bolt that holds the front valence bracket, after the requisite scraping and Waxoyl/WD40 application.This obviously involves cutting the red-yellow at this point, but the remaining section that goes within the harness up to the lighting-switch will come in useful another day for some added but discrete function.

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The modifications are resumed here, see red zones :

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Headlamp feeds, Wiring, Bonnet Plug, Relays

There's a complete run-down by David of using modern relays in the bonnet nose here, for those that prefer that approach.

http://etypeuk.com/forum/viewtopic.php? ... onnet+plug

I wanted something more accessible so had to use old-style relays.

Even though the wiring throughout the bonnet was perfect, I have no faith in crimped bullets so systematically bared all the noses (file-card is great for this), fluxed them with non-corrosive stuff, and soldered the wire/bullet interfaces on all the earth and headlamp-wiring junctions.

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I used new headlamp wiring back to the last bullets, soldered all the flags, changed all the female bullet-sleeves, and ran a mixture of Waxoyl and WD40 into all the crevices - so as to avoid this kind of thing.

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I used a new bonnet-plug, probably quite unnecessarily as was detailed here

http://etypeuk.com/forum/viewtopic.php? ... onnet+plug

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and paid particular attention to the soldered wire ends and the screw connections.

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Not wanting to locate relays within the confines of the bonnet, I used Lucas copies which sit well with the engine bay next to the original horn relay. The original blue/red and blue/white headlamp feeds are easily hooked out of the harness at this point, by choosing your entry strategically you only actually have to lengthen one end of each with a soldered and heat-shrunk splice, hence the main/dip choice comes down as a very low current via the dip-switch, on the original wires, removing all the heavy loads from the cockpit switches, then trips the relay, which then sends the heavy current down the continuation of those wires via the bonnet plug to the headlamps.

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The modifications are resumed here, see pale-blue zone :

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Ignition-Switch Relay

This has been addressed several times elsewhere, I include mine only because I wasn't able to do it quite as neatly as others for reasons of original wire-lengths so had to resort to fitting the relay on an instrument-mounting post - there is sufficient depth to tolerate this and it might encourage others to try what is a most useful mod ; even if the really heavy currents like headlamps have been offloaded with other relays, I think this is worth doing.

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The modifications are resumed here, see brown zone :

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Fuel-Pump Cut-Out and Warning Light

The interruption of the feed to the fuel-pump is a well-known anti-theft modification, which has the multiple benefits of allowing you to empty the float-bowls a bit as you get home, allowing someone to car-jack you but only drive 200 yards, and allowing someone to steal your car at night but only get it half out of the yard - which is exactly what happened to a tenant of mine in a lock-up where the pump-switch on his Alfa GTV allowed the thief (brother-in-law as it turned out !) to start the car and only drive it 50m, whereupon his insistant starting-attempts woke me up to chase him off.

You can hide or disguise your switch wherever you want as long as you can get the wires up to the N°4 fuse, which is where the fuel-pump usually goes from.

I like to know whether I've got the fuel-pump switched on, and since I have no faith in the low-fuel-warning-light had no regrets in transforming that one into a Fuel-Pump-Off light by the simple expedient of rewiring it and using a 6v 2.2W bulb (12v was a bit dim when in series with my pump) in parallel with the kill-switch - when the pump is "Off" it lights up to remind me that this is why the car won't start.

The modifications are resumed here, see pale-green zones :

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Kenlowe Fan Feed

I left the original fan-relay on the header-tank cradle, but use its original green wire to drive the Kenlowe relay ; by connecting that green to the (redundant for me) purple cigar-lighter feeds, in the dash/fuses area, it can be made permanently live, then by using the C1 relay terminal as a connection point with the original black-green feed to the fan, full use can be made of the original harness as far as the Kenlowe relay.

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The modifications are resumed here, see orange zones :

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Coil and Ignition Feeds

The white wire in the original harness gave an unusually high voltage drop to the coil and Aldon-Igniter that I have fitted, being rather weedy and anyway having next-to-impossible access to improve its spade terminal connection on fuse N°6, where it starts as standard. However, by identifying the much thicker green feed to the stop-light switch on the front picture-frame, and taking it to the feed-side of fuse N°6, all it requires is a piggy-back spade connector on the ignition feed-wire for the ignition to be discreetly and conveniently taken off the stop-light circuit.

See previous picture of wiring around the redundant fan-relay.

The modifications are resumed here, see pale-blue zones :

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Instrument Voltage Regulators

A generous Forum member gave me two solid-state adjustable VRs for fuel-gauge and temperature-gauge feeds, which means you can play with fine-tuning the readings on each - a bit of a gimmick but ??? when the fuel-gauge says "full", I now know that it really is. Really dumb actually, far more intelligent to fine tune the "empty" reading .....

The modifications are resumed here, see purple zone :

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I'd welcome any observations about potential unexpected side-effects of what I've done, and why - perhaps - what I perceive as shortcomings in the original fusing may have been deliberate, though after several hundred kilometers with these changes active everything behaves as it should ; sleeping above where the car lives as we do here, in a country where building-regulations, fire-doors etc have not yet percolated down, I'm happier to know that everything is now sitting behind a fuse, and that - to the uninitiated - things look undisturbed and original.

PS - Note written almost 4 (Edit - now 6) years later - still v.happy with all that, no issues whatsoever.
Last edited by rfs1957 on Tue Apr 21, 2020 4:29 pm, edited 24 times in total.
Rory
3.8 OTS S1 Opalescent Silver Grey - built May 28th 1962

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64etype
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#2

Post by 64etype » Mon Jan 06, 2014 4:51 pm

Excellent description and a very well executed upgrade. As I am putting the finishing touches on a similar wiring redesign (the Bob Skelly architecture on steroids), I will incorporate your idea to use the fog lamp wire as an extra ground to the bonnet, and will add a fuel pump and possibly an ignition cut-off switch...maybe both depending on how paranoid I'm feeling that day. I like the idea that if a thief gets it started, the perpetrator would then be looking at a low fuel light....even before attempting the short lived getaway.
Eric

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#3

Post by rfs1957 » Mon Jul 14, 2014 9:41 am

Just to confirm that 2 or 3.000 km down the road, all these modifications work perfectly and have required no intervention or tweaking since I put them into pratcice.
Rory
3.8 OTS S1 Opalescent Silver Grey - built May 28th 1962

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#4 Re: Series 1 3.8 Wiring Modifications, Headlamp Relays etc

Post by rfs1957 » Tue Dec 05, 2017 10:41 pm

I've just re-freshed all the missing ex-PhotoBox pictures on this thread, a real dockyard job, and here's another useful add-on for the wiring addicts amongst you :

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Dual USB charger hidden under the passenger knee-board, the link to the supplier is here on this post.

viewtopic.php?f=2&t=9246&hilit=USB+socket

Hole visible on this pre-trimming shot.

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Rory
3.8 OTS S1 Opalescent Silver Grey - built May 28th 1962

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