Lighting

Wiring Differences

First, I disassembled the stock halogen light and compared the wiring to my aftermarket LED headlights: JW Speaker #8631

It was helpful to have a wide blade (plastic) auto trim tool to help pry the two halves of the bowl apart.

OEM Halogen Headlight

• Black = Ground, connected through ground screw in bowl
• Blue w/White = Main Beam
• Blue w/Red = Dipped Beam
• Red = Sidelight
• Separate (indicator pod) = Turn Signal

Replacement LED (JW Speaker Model 8631 Evolution)

• Black = Ground
• White = Main Beam
• Yellow = Dipped Beam
• Red = Front Position Light
• Purple = Daytime Running Light
• Orange w/White = Turn Signal

The Plan

My plan was (i) to ditch the indicator pod and instead make use of the LED headlights (integrated) circular yellow turn signal, and (ii) to wire the much brighter DRL in place of the OEM sidelight thereby improving safety.

I had two main problems to solve:

• Threading the new LED wiring up into the headlight bracket and then down through this bracket and out into the engine bay

I think the difficulty of threading the wiring bundle, somehow, through the bracket – plus integrating the turn signal wire – is why this part of the build gets called “tricky”. It seemed like the main difficulty was that the wires were already “pinned”. The pins on the end of the existing wires are large enough that they have to be shuffled one by one down through the bracket. All of which makes it difficult to also sheath and protect the bundle with the supplied black tubing.

• Connecting the new LED wiring to the existing wiring scheme

Instead of splicing into the existing wiring at the headlight bowl and bundling up the LED wires there, I decided to go for a cleaner approach! I planned to cut the supplied connectors from the new LED headlights – leaving simply wire – sheath this whole length in heat shrink, push through the bracket and repin the wires in the engine bay.

Steps

To switch over the LED headlight I first needed to separate the OEM headlight bowl from the front cover / trim ring that it is housed within. The OEM headlight is held in place by three fiendish “W” clips. These were fairly easy to remove using a pick tool, at which point I moved the front cover / trim ring over onto the replacement LED headlight. But reinstalling the “W” clips was frustrating! There is a trick to installing these, but I think everyone fumbles around with this before finding the right approach and tools for them. For me I used a very small pry bar to lever the clip into place but eventually learned how to roll my thumb over the lip to push the clip in. YMMV. Have fun! Experiment! You can only improve …

With the LED headlight switched over into the headlight bowl housing:

• Cut the supplied connectors to the LED headlight leaving bare wires. Including the ground wire as this now travels with the other wires to connect to ground at the chassis connector.
• Covered wires with 1/2″ heat shrink tubing using enough length (in my case ~ 19″) to cover from the interior of the headlight bowl with ~ 1-2 inches of uncovered wire in the engine bay.
• Applied heat to shrink the tubing
• Threaded the wire bundle out of the headlight housing i.e. through the rubber bung and headlight swivel mount
• Added grommet (to be pushed into underside of headlight bracket)
• Sprayed silicone lube into the headlight bracket
• Threaded the wire bundle through headlight bracket and into engine bay
• Added grommet (to be pushed into the bottom / engine bay side of the headlight bracket mount)
• Terminated with Econoseal seals & pins (practice using the crimp tool first!)
• Assembled pinned wires into the correct position on the supplied Econoseal connector – which was in an anonymous baggie, no instructions, taped nr. the radiator and horn connectors. See “Wiring Convention” below for details on how to match the wires.

Thanks to BigCol’s post on Caterham and Lotus Sevens board which does a great job of explaining how fit Econoseal connectors.

The wires were pinned with the correct Econoseal seals & pins, using a generic crimping tool. There are only a few sources for these pins in the USA, including Corsa Technic who specialize in autosports and military:

• Crimping tool used was an Open Barrel “Type F” crimper which are blisteringly expensive for production quality tools but happily can be found as inexpensive “hobby” versions. I am sure these are less precise but the only real difference is they require separate operations to crimp the wire and then the seal.
• Caterham use the Econoseal “J Series Mk II” which come in two sizes: TE070-PIN1 (with seal TE070-SL1) for 20-24 AWG wire and TE070-PIN2 (with seal TE070-SL2) for 20-16 AWG wire. I used the larger PIN2 / SL2 size of pin and seal.

I made a mistake (left out the seal) on one wire and attempted to pull the wire from the pin and start over. I was very surprised at how secure the crimped pin was – ultimately I gave up trying to pull it out and worked the rubber seal over the pin.

Wiring Convention

The Prince of Darkness Lives!

In researching the various aspects of the above I was surprised (but shouldn’t have been) to find that Caterham still follow Lucas Industries (aka “The Prince of Darkness”) wiring conventions for color:

• Main Beam = blue w/white stripe
• Dipped Beam = blue w/red stripe
• Turn Signal = green w/red stripe on LHS and green w/white stripe on RHS
• Sidelight = red
• Ground = black, tested good at the chassis connector with ~ 1 ohm

Lucas colors may be helpful in tracking other wires throughout the vehicle. Lots of information can be found using google to search for: lucas industries wire colors.

Finished Product

I’m happy with the result! Although I need to figure out a way to “black” the large nut beneath the headlight.

The replacement LEDs are a vast improvement on the OEM halogen headlights. And the dim sidelights are now wired as much more useful and brighter Daytime Running Lights.

The wiring into the chassis connector is clean and looks “OEM” using the correct pins and connector with no additional points of failure introduced.

I prefer the way the front-end looks without the indicator pod. The stock plastic pod doesn’t look bad but IMHO doesn’t add anything either.