WIRED and TiReD.. Lotus Plus 2S130 Now with Dash Dilemnas

[mjbeanie]

Hi Everyone,

Hope you’re all safe and well. So I’ve finally started attacking my ebay purchase from two years ago. My Lotus Plus 2S appears to be an August 1971, Type 50 , ID # 0179N, Big Valve power plant, (standard compression), Federal example. (Early Plus2 S130, 4 speed per Andy Graham at the Registry.) Powerplant is original, Engine u/24-911. This was sold as a complete, but very unfinished, partial restoration project.

The car needs a lot of everything. So I thank you advance for any help, suggestions or recommendations.
I’ve decided to start with the tired electrics. (I know my limitations so I willl leave the engine and chassis work to the experts at Flying Circus British Restoration.)

-The dash is quite nice, and I’ve purchased both the engine bay loom and dash wiring loom and have spent many hours hashing thru connections using the old harness and a poster sized enlargement print of the schematic . I took out the old dash harness to help me sort this mess. It has an alternator and 3 fuseboxes in Engine Bay.

In any case I hope you all can help me. I’ve decoded a lot of stuff and made decent progress but remain stuck in a few areas. Thanks in advance for your help, suggestions and guidance.

The car is gutted inside and is a fiberglass bathtub. However the car is complete and I have most of the stuff in boxes. Anyway back to the harnesses. I’ve compiled a list and any insight is appreciated.

1. First I need some help identifying some things. Is the photo below a seat belt buzzer? Can’t see a pn. I have square flasher units on dash so I don’t think that’s it. It has one wire coming off terminal 4 on the old ignition switch.

2. Mystery toggle switch: I have two rockers for FOG and SPOT, but have no clue what this toggle does. Can’t find it on the print. Color code is purple/blue and black. My guess is it has something to do with the headlamps/headlamp relay. It does appear to be OEM, and not a mod of any sort.

3. The Coil has three wires all yellow and white that need connection. I don’t know if all three are used. The schematic is no help. There is no way to differentiate them for connection to positive or negative terminals. I have a “CVI” Current driven tach, and still am not sure what post (+ or -) on the coil provides the signal. I’ve read a lot of articles, and have completely confused myself finding an answer.

4. It also seems like the sidelamp microswitches and headlamp microswitches were never installed/connected to the old harness. These connections were taped over. I am not even sure the switches exist. Is this a common thing to bypass them? Are they really needed?

5. Also have a bear of a time wiring the hazard switch. I was considering using 036M 6271R as replacement switch from Ray D. Enterprises. Once again the wiring schematic was not a big help in this arena, as the folks at British Wiring made some wiring color substitutions of their own, that do not follow the print or the old harness wiring. The connections I have to work with are the following:

-Two green/red stripe wires
-Two green white stripe wires
-Yellow/black stripe from flasher unit

Not sure if I am missing any others

On the forum many have said “Run the dash out of the car.” Aside from basic continuity checks- are there any other methods out there to check it before install? Is there a recommendation I could follow.

Thanks all for the help. This has been a big job and quite a puzzle. Any PHOTOS are also really appreciated.

I can’t help but wonder if this thing is going to burn to the ground once I flip on the wipers…

(maybe I just won’t flip on the wipers…)

Cheers
Mike

[stugilmour]

Mike, are you using a standard wire colour table like this one?

autoelectricsupplies.co.uk/ … rder_2.pdf

Lotus does not 100% follow the standard colours, but can be a big help.

1. Not sure.
2. Purple/Blue calls up as standard colour for the heated rear screen. Not sure in your particular model though.
3. Thinking positive coil terminal. Are you saying white wires and yellow wires, or a white with yellow trace? Or perhaps all three? White/Yellow calls up for power to ballast resistor, ie key to the coil thru the ballast resistor.
4. Not sure your model, but the Federal sidelight and headlamp circuit is quirky, involving a sort of latching relay setup. Is your car equipped with a flat rocker switch that is spring loaded? ie switch sits in middle position and you press to turn on the sidelights and press other side of switch to turn off? Can help if this is what you have.
5. -Two green/red stripe wires = left hand flasher lights
   -Two green white stripe wires = right hand flasher lamps
   -Yellow/black stripe from flasher unit

Hopefully the attached will help as well. Not sure if you have them. I can make better scans of them if you do not have them already. Note they may not be your exact model though.

[mbell]

2. The latter s130 use a toggle switch for the side and head lights. One click is side lights, second is headlights.

[mjbeanie]

Thanks so very much for the detailed responses!

#1 I think its a seatbelt buzzer, but looks like an early flasher!
#2 is still a mystery toggle, I am still thinking something with headlamps. Rear screen wiring appears ok.
#3 I have quantity of 3 wires that are white with yellow striping. All identical, and of different wire lengths.
It is still an open question. Think they all go to the coil somehow, since there is nothing left in the area to connect to-lol
#4 I do have a rocker switch spring loaded that sits in the middle for sidelight actuation.
#5 Solved. Yay!

Thanks for the wiring photos and table. VERY helpful!

I would very much appreciate a scan of the first diagram. It does appear to be a match with my car.
Wondering were that document is from? I have a shop manual and parts book, -and couldn’t find it. Thanks again.

Best regards
Mike

[HCA]

The white/yellow wires - these are in the new wiring loom you have, yes?

If so, I think you need to ask the manufacturer what they intended exactly.

Generally white/yellow is used between ballast and coil, but not very often (I think it might be a later convention). However there was a mod made for cars with ballasts, that gave a full 12V to the coil whilst cranking. Used a lot on Triumphs. The cable was white/yellow.

Can you trace back where the white/yellow cables go to on your loom? It could be that the manufacture inserted three cables to account for three different positions where the coil could be installed. I do not know, just thinking how I would do it. Ask the manufacturer.

[RichardHawkins]

Mike,

My car is an S4 Elan, not a plus 2. There is a man in Britain called Brian Buckland who has written a large book on the two seat car. In the electrical section he advises that having done wiring work before you risk burning your car to the ground you fit a small fuse between the battery and the main cable. Then you can test all circuits and if there is a fault the worst that happens is this small fuse will fail.

I am still struggling with wiring of my car and will follow this advice. I also hope to check everything works before finally screwing the dash into place.

Hope this helps,

Richard Hawkins

[stugilmour]

Regarding the white/yellow ignition wire set(s), note the coil power may go through a ballast resistor setup and through the burglar alarm switch (AE on the connection diagram). Up to you, but a lot of folks eliminate the burglar alarm feature during rewiring. Might be a separate topic to sort out details?

The connection diagrams were in my aftermarket parts book in a section called service notes. The particular +2S drawing is also thrown in at the end of section M electrical equipment, but again my manual is aftermarket. Anyway, it was a usable diagram fir my Plus 2 Federal (four small gauge setup) for the switches, but not the gauges. The Plus 2 has a lot of variants, and therefore your replacement loom might need a few changes or puzzling to get right.

Given you have the flat intermittent rocker switch for the sidelights and presumably the vacuum pull switch for the headlights, I will dig up a few older threads that might help/apply. The vacuum switch should have two micro switches attached; this replaces the original setup that had micro switches that were worked by the movement of the pods. It sounds like a previous owner may have changed things a bit, and not sure how your new loom will be set up. A suggestion might be to add a new post directly to the end of one of the older threads to bring it forward and ask any detailed questions?

Just a quick aside. Don’t be surprised if Jeff moves this thread from the Plus 2 section to the electrical section to keep the info in one place. Generally repair & service threads go in he detailed sections, and general banter in the Plus 2 section. Not a big deal.

HTH

[stugilmour]

Here is a hopefully better scan of the connection diagram

Unfortunately the search function is down right now. I will try to find the sidelight threads later.

Stu
Connection Diagram.pdf (609 KB)

[mjbeanie]

Thanks very much Stu. This is very helpful!!

Also was wondering specifically what amp fuse to put inline with the positive power lead when I ring out the dashboard, perhaps a low 2-5 amps?

I am almost ready to integrate into the car-
“Shocking positively shocking…” (007-Goldfinger)

[mjbeanie]

Appreciate the guidance on forum topic posting. It is also appreciated.

[stugilmour]

This thread has some very good photos of the Plus 2 vacuum switch and microswitch setup

viewtopic.php?t=15992&p=80164

This thread references a bit on how the circuit works, and links I think to a thread with more information

viewtopic.php?f=38&t=30081&start=

viewtopic.php?f=38&t=30081&start=

This one has some more pictures and discussion

viewtopic.php?f=38&t=40543

This thread was the hardest to find but may be the best photo library of the vacuum switch

viewtopic.php?f=38&t=30012&start=

Hoping this all helps. The operation of the circuit is described in the WSM. I did up a wiring diagram in PowerPoint that attempts to describe the latching relay and two micro switches attached to to vacuum switch. In addition another poster did up a more schematic type diagram that you may find easier. I can find those threads as well if they are not included in the above links.

Seems to me you have three broad things to consider

How was my car wired originally and what has the previous owner possibly changed.

How is my new loom designed and how does it differ from above.

Considering the above, how do I want to configure the wiring in my new car

The Plus 2 headlight and sidelight circuit is particularly strange as originally it used micro switches in the pods, then moved micro switches to the vacuum switch, and then apparently changed to a more conventional switch with settings for side lights and head lights. Kind of a select the version you like deal maybe?

HTH

PS. I eventually used the Google search technique where you type in your search terms followed by “site:lotuselan.net/forums” as the forum search is not working for me. The other search method is to click on the photo gallery and slowly type in a search term and the available pictures will filter down by thread topic.

[stugilmour]

Plus one for Goldfinger Mike. “No Mr Bond, I expect you to die”

Yes, just a small inline fuse like 2 to 5 amps for testing. It is basically placed inline on the main Brown Hot at All Times - Unfused that supplies power to the whole loom. You can’t really function test the charging system or the starter out of the car, but everything else works with the dash out and the loom stretched out on the floor. I was amazed how many mistakes I had to correct.

HTH

[HCA]

A good idea fusing the main feed, and if you do this sort of thing regularly, or have problematic devices to check or want to find a problematic device - invest a small bit in a 12V auto circuit breaker. Tape it into a small plastic box with quality insulated croc clips and it will pay for itself in no time!

[stugilmour]

Agree with the above. I opted for protecting the loom with a 50 or 60 amp fusible link. I think I saw this strategy on my 80’s BMW.