Lotus Elan

Wiring Loom Plus 2

PostPost by: Marcus+2 » Thu Jul 04, 2024 2:24 pm

After hours of fiddling, biting the bullet and taking it for professional help, the diagnosis is that it would be best to fit a completely new wiring loom and start from scratch.

So, the embarrassing thing is, I don't really know what version of car it is, so can't order the loom!!

It is 1968, RHD, it has 2 fuses and an alternator, I believe it has a voltage stabilizer? (black box bolted to bulkhead - Pic 3), so its not a US model.

Can anyone advise on version, and sourcing wiring loom (Klevedon Lotus?)

Many thanks
1000013326.jpg and
Coil and aftermarket relays
1000013327.jpg and
Voltage stabilizer maybe?
1000013328.jpg and
Relays and alternator
Lotus.jpg and
2 fuses under shabby wiring
Posts: 13
Joined: 11 Apr 2024
Location: North Wales

PostPost by: Lotus fan » Thu Jul 04, 2024 3:13 pm

Autosparks made the original wiring harnesses.
It's where I bought mine from and no issues whatsoever.

User avatar
Lotus fan
Second Gear
Second Gear
Posts: 127
Joined: 14 Sep 2003
Location: Wrexham. North Wales.

PostPost by: GLB » Thu Jul 04, 2024 3:53 pm

I too bought mine from Autosparks for my 71 +2s and it fit perfectly. Just be sure to buy the correct one as there are several different wiring schemes.
Second Gear
Second Gear
Posts: 176
Joined: 31 Jan 2018
Location: El Paso, TX USA

PostPost by: Marcus+2 » Sat Jul 06, 2024 9:51 am

Thanks for the replies.
I think Klevedon do them as well, but I need to order the right one, so was interested in what type of loom I need.

Any help would be appreciated - TIA.
Posts: 13
Joined: 11 Apr 2024
Location: North Wales

PostPost by: stugilmour » Sat Jul 06, 2024 5:24 pm

No direct experience with the Autosparks looms, but have read a lot of threads referencing them. I actually was too daunted by your exact concern when I was new to the car and wanted to install all new wiring as mine appeared to be pretty bodged over the years. I went with a Spyder supplied loom instead, which ended up working out OK but needed a lot of modifications. Just offered as background, not a recommendation.

My understanding is the same variety of Autosparks Plus 2 looms are sold in North America by British Wiring. Their website below might help you in determining the best three looms to order as in some respects the descriptions seem a bit better. The Kelventon descriptions also help, and I assume they are also Autosparks, so thinking it is an order wherever you prefer type deal.


If I understand your question, sounds like an exact description of a few key details for your car would help a bunch. I am expecting whatever loom variants you select some modification may be required. I don’t think this will be that big a deal because all the descriptions describe them as wrapped with hopefully non-adhesive loom tape. This allows generally quite easy modification of the loom as required.

Can you describe your car in broad details a bit? Obviously some of these you already provided

  • RHD
  • 1968 Assuming this is based on registration date rather than build date? Can make a difference.
  • Only a single fuse box with two glass fuses? You may want to change this or not.
  • Full VIN (50/####) Your car can be compared to the published Robinshaw & Ross listing of rough introduction dates and serial numbers to describe the model and the key needed features.
  • Four minor gauges or six? This is probably the biggest difference maker in the dash loom selections.
  • Ammeter or “Battery Condition Meter” (voltmeter)? Two part question; what do you have now and what would you like to install? Lotus advised in the WSM to charge to a voltmeter if an alternator is installed retroactively.
  • Emergency flashers present?
  • A picture showing the light switch arrangements for the sidelights and the headlights, and perhaps a picture of the microswitches that are probably at the front of the bonnet closure (sort of like the door switches).
  • Rat tail toggle style or flat rocker switches? This is probably the second biggest detail in the dash loom portion.
  • Front fog/driving lights installed?
  • Presence or absence of the later additional auxiliary lighting (under the bonnet, boot, doors, glove box). Think this is all absent on your car by the age?
  • Presence or absence of an actual element for rear screen defrost heat and presence or absence of a dedicated dash switch. e.g. My Federal car didn’t have the element or wiring, but the switch was there.
  • A few general layout pictures of the dash to determine the various warning lights, switches, etc.

The biggest remaining difference between the looms seems to be the generator or alternator arrangements. Perhaps take a few additional pictures of the Regulator Box and the actual alternator with its wiring and someone way more knowledgeable than me can help you out.

Most more modern alternator conversions use a lightweight and compact NipponDenso based alternator kit that has the regulator inside the case. This makes the wiring way simpler. I think your setup is different, and may be either requiring the external regulator you have identified on the firewall, or the guts of the regulator have been modified. If you are comfortable and and able, a few pictures of what is presently connected to this regulator and a picture with the cover removed will assist in identifying what you have. That said, you can simply “upgrade” to the NipponDenso style arrangement in conjunction with your rewire.

As usual, sorry for the length, but without a few more details it is probably kind of hard for the Autosparks cognoscenti on here to provide a helpful answer beyond that they all generally describe the Autosparks looms as good quality but hard to identify.

As I say, I had exactly the same concerns when new to my car. When I actually gained a better understanding of a few Plus 2 wiring quirks (from excellent answers here on the forum) and had the original looms totally out of the car I found out that my original wiring (eliminating all the previous owners modifications and bodges) actually followed the Lotus WSM Federal Plus 2 exactly. Still glad I upgraded things, but I probably could have started with the correctly selected Autosparks looms if I could better answer a few identifying features. At any rate, I am sure the forum can easily help you out enough to knowledgeably discuss your specific requirements with the various suppliers.

Once you get your selected loom suite, you can pretty easily make note of what you might want to add or modify in conjunction with your rewire. Some common adders and changes include the following, and all have lots of separate threads with details. The main point is to decide on your final scope before putting your new looms into the car and installing the dash. Not a general recommendation of changes, just a shot at a list to consider or dismiss…

  • Wiring for an electric fuel pump.
  • Deleting the security switch in the glove box.
  • Changes to the ground location(s) and/or wire runs.
  • Any change from stock for the Otter Switch/Cooling Fan control.
  • Electric light pod lifts.
  • Changes to the headlight/pod/ sidelight switching if something is worn out.
  • Alternator “upgrade” or change.
  • Voltmeter.
  • Modern radio/ head unit/ speakers / etc.
  • Some USB’s or power points to charge a phone, plug in a Garmin, etc.
  • Wideband O2.
  • Electronic ignition, which might need/prefer an extra power wire.
  • Tach electronics upgrade or any required loom changes to accommodate later.
  • Whether to eliminate any of the bullet connectors in favour of more modern block connectors. Some of the guys that have Autosparks looms can better describe details, but having easily separated block connectors to allow easier removal of the dash has a lot of merit if the Autosparks wires are long enough? Has to be done in conjunction with loom installation to be able to feed the wires thru the firewall before attachment of the connectors though, so needs to be thought thru.
  • Whether to add any relays to lighten the load on various switches.
  • Any changes to the stock flasher circuits, including turn signals, emergency flashers abd on some models a flash to pass style feature.
  • Delete the firewall mounted voltage regulator completely or modify internally to suit the alternator option selected.
  • Upgrade the 10v voltage stabilizer to solid state. This is a small box attached to the tach that provides 10v stabilized supply to the fuel and electrical temperature gauge. Might need a minor local wiring change for the ground.

1969 Plus 2 Federal LHD
User avatar
Coveted Fifth Gear
Coveted Fifth Gear
Posts: 2103
Joined: 03 Sep 2007
Location: Calgary Alberta Canada

PostPost by: Ceej » Sun Jul 07, 2024 9:51 pm

From your photos it looks like the alternator may be a retrofit: the second photo shows what appears to be an inline fuse (from alternator to solenoid?) sitting on top of the voltage regulator. This is sometimes done when a dynamo has been replaced by an alternator; usually an alternator eliminates the need for the existing voltage regulator, although sometimes people retain it for originality where it can be used as a distribution block.

Going solely on the info & photos provided it looks like the car is a 2 glass fuse dynamo car that has been altered. Check to see if the voltage regulator is a 'Lucas RB106' or 'Lucas RB340'. Also, an ammeter in the dash is further evidence of this being an alternator conversion.

I have a 69 build Plus 2 Federal car. Of the 7 or 8 wiring diagrams I have, or have seen, NONE of them match my car; a 69 build Plus 2 'Didn't-quite-make-it-to-an' S. Given that your car is probably a home market car you may be able to find a diagram that closely (or maybe even exactly, if you believe in miracles) either hereabouts via a search, or in workshop manual(s).

Some months back I posted a colo(u)rized version of an early +2 wiring diagram that was initially posted by Bud English. It *might* help you by matching the instruments / devices / lights shown against what your car actually has. FWIW, the diagram says 'Elan Plus 2 RB106 Control Box Sept 67 - March 68'.

Find it here:


Please note that the diagram in the link is for a Positive Earth car (mine isn't), yet another variable for you to, um, enjoy. Differences are minor by and large and the wiring of instruments, lights et. al. would mostly be the same. I think. :-/

HTH & Cheers!
Posts: 12
Joined: 29 Mar 2023
Location: United States

PostPost by: Marcus+2 » Mon Jul 08, 2024 4:22 pm

Wow - thanks very much you two - I am really grateful!

The car has an ammeter display, so the alternator must be a conversion.

It also doesn't have hazard warning lights, extra fog lights, lights in glovebox or anything fancy like that - so that should make it easier hopefully.
I will buy a voltmeter to replace the ammeter in the dash.
They are proper chrome toggle switches rather than a rocker type.

I will definitely look at the control box to see which type it is - the car is in my garage which is not near my house, so will check this later.

Thanks again for the info - this is very valuable to me.
Posts: 13
Joined: 11 Apr 2024
Location: North Wales

PostPost by: stugilmour » Mon Jul 08, 2024 5:36 pm

Great Marcus. Glad we could help.

I also thought your alternator is a conversion. My memory is a bit foggy now, but your installed alternator looks a bit like the one that was in my car when I bought it. Mine was some kind of Delco unit, source unknown. I was never sure how it worked/interacted with the firewall mounted Lucas voltage regulator, which I completely removed from the new wiring setup.

The alternator also fouled the steering shaft in my LHD car, and the fan belt length made it difficult to install. The rewire and a new alternator kit made things way better, although I am in the process of fixing up the tensioner to make fan belt fitment a ton easier. I stupidly “modified” the tensioner when I installed the kit because I was not using the correct length belt.

If you do go for a new NipponDenso alternator kit, suggest getting a new belt that the supplier says will suit their kit. For reference, the kit commonly available in North America uses a toothed belt marked “Bando RPF 2305, 9.5 x 775 La”.

Great idea to convert to a voltmeter. This removes the main charging wire (from the alternator to the solenoid thru the ammeter) from the back of the wooden dash panel. As Ceej described it is typically replaced by a heavy gauge conductor that is inserted in protective plastic tubing and run similar to your Red wire with the fuse. Usually this wire colour would be Brown, possibly with a tracer colour; in the British wiring schema the Brown series are reserved for “Hot at all times, unfused”. Red conductors in a Lotus typically scream previous owner modification.

These listing of standard wire colours are pretty complete and great for reference …


https://www.autoelectricsupplies.co.uk/ ... rder_2.pdf


For sourcing a voltmeter, I tried a using “period correct” Smiths Battery Condition Gauge. It didn’t work well (well, worked if you tapped it sort of thing), and had a different needle pivot cover shape on the face so it looked mismatched to the other gauges. I changed the needle pivot cover (using the cover from my ammeter), but was never really happy with the results.

This new one from the currently manufactured Smiths range is a much better complement to the other gauges. Note you may have to change the gauge lighting socket though, can’t recall the details but a relatively easy change with the dash out but very difficult when in place as the glovebox is in the way.


1969 Plus 2 Federal LHD
User avatar
Coveted Fifth Gear
Coveted Fifth Gear
Posts: 2103
Joined: 03 Sep 2007
Location: Calgary Alberta Canada

Total Online:

Users browsing this forum: ken_apple and 7 guests