UK vs US wiring harness

[JeffP]

I'm not an auto electric expert. I'm restoring a 1969 Elan Plus2 it was shipped to Canada and I call it quasi-federal. The early Plus2 wiring diagram is the most accurate diagram better than that for the federal or non-federal spec in the manual. It has had an alternator conversion sometime in it's life. I'm in Canada, so here is my question

If I buy a new wiring harness is it better to buy a repro harness from e.g auto sparks in the UK or use a customizable harness from e.g Painless or Haywire, in the US with modern fuses/relays/connectors etc?

Thanks

[pianoderby]

I will be putting a haywire harness in my S3. I can’t speak to it being better or worse than something more original, but the electrical is somewhere that I’m willing to modernize. It does mean doing everything from scratch though.

[stugilmour]

Personally I would prefer to stick with the British wire colours rather than introduce a whole different wire colour convention.

It looks like Autosparks, in addition to making model specific looms, makes some more generic kit car style looms that presumably mostly use the standard British wire colour code. Could use this as a starting point if you want to add more fuses than your Plus 2 version might offer.

When I totally rewired my ‘69 Federal Plus 2 I started with a generic kit car loom supplied by Spyder. Not sure what they may have available now, but they basically rewire the entire car when they build up a Zetec. I ended up modifying the loom quite a bit, but it was very helpful to have a starting point. One feature I liked was the loom included several common ground runs; pretty much the whole loom only uses the dashboard mount ground. I would add a similar common ground network to whatever I got as a starting point.

Having seen several threads over the years regarding the Autosparks looms for the Plus 2, I would be prepared to want to modify the loom a bit just because of the different Plus 2 looms over the years. Not a big deal once you unwrap the whole thing I suppose. Once over this hurdle it is actually pretty easy to move stuff around before installing the loom.

Perhaps some of the UK based members a better idea of other kit car suppliers with looms that largely follow the BS-AU7 colour convention. Searching around a bit I see som manufacturers sell just the loom relay/fuse box and one can simply build up a loom circuit by circuit, but that sounds a bit over complicated for such an essentially simple car model.

In terms of circuit modifications from stock I would consider, or may need modification (best I can remember)…

• Headlamp on / off depending on location of your microswitches.
• Sidelight on / off depending on your switch package. The Federal flat switches use a slightly quirky relay setup tied to intermittent dash switch. Yours may be more conventional. I used the stock configuration which required extensive loom changes.
• Two speed wiper circuit is pretty conventional, but Lotus used some non-standard wire colours. May have to move for LHD wiper motor position.
• Alternator and/or regulator delete. I would just remove any vestige of the generator and/or regulator from the car and wire for a modern NipponDenso unit with only two wires.
• Location of any fuses or relays. I put them in the glove box area to keep out of the weather.
• Turn signals and hazard flasher. My loom used a single flasher relay for both functions so quite a change from stock. Required several relays to work with the simple stock dash switch. Note most modern looms use two dash pilot lights (for left or right turn), so some diodes may be needed to get the stock single pilot to work.
• Electric window lift wiring was not included but not a big deal to add. Lotus did not use standard colours anyway. I used relays to lighten the load on the dash switches.
• Most generic looms include a relay switched to ground for the horn circuit, so no issues. I removed any vestige of the anti-theft switch in the glove box.
• I used a main White / Red from the dash ignition switch to an enlarged accessory bus for the radio and any other additional widgets for modern electronics.
• Add a separate circuit to power an electronic ignition module independent of the coil or tach sensor wire.
• Wire the instrument lighting with separate grounds for each bulb. Way easier to service than stock ring terminals on the gauge mounting screws. Also allows easier addition of a solid state dimmer on the ground side if that floats your boat. Not required but nice if you go with dash LED’s.
• Most generic looms are equipped with a thermostatically controlled electric fan circuit. Should use a relay. Depending on the location of your Otter switch (or equivalent) you may need to add wire length to the sensor wire.
• I would definitely have relays for high and low beam. Might need some modification.
• Consider adding a hot at all times- fused purple under the dash or wherever you are locating the fuse & relay box. I used this for electric door locks. Handy to have and easy to add now.
• I added relays for the heater fan, but I don’t think they were really required or add much.
• Consider running a radio trigger wire to the trunk. I used it for an amp.
• Might need to run a low fuel light wire if you use a generic loom.
• Some of the generic looms expect the ignition key to be part of the column loom, so may need relocation to the dash.
• Doubtful the brake fail circuit will be in the required location. Changed over time in the Plus 2 anyway.
• Reverse light switch run needed more length. Not a big issue to add a connector as it needs an easy place to u fasten to remove the drivetrain anyway.
  

I just used the BS-AU7 colours throughout if I needed to add wire. I used the orange series for electric pod motors as I don’t think Lotus used them.

Quick note on documentation. Rather than get bogged down with a single page schematic I made separate drawings for the main circuit groups on 11 x 17 card stock. Works well. With hindsight, I would recommend being very exacting in documenting each connector and the various wire colours and pins. It turns out that is what you need available if you are troubleshooting or adding a feature in the future.

Cheers from Calgary. HTH