Lotus Elan and Lotus Elan Plus 2 Forums

My files were created in Photoshop, not some CAD program.
It seems that the maximum file size to upload is 2MB.
Even a scaled down PDF file is 3MB.
PM me if you want me to email you a larger file.


Thanks,
Eric

Eric,

Thank you, have sent you a PM.

billwill and h20hamelan,

Thanks for your helpful suggestions. I can open the image and save it on my iPad and once there can expand it but it loses sufficient definition to be illegible beyond a certain point. Eric has kindly offered to e mail me a copy. I currently have the entire drive train out of my car as taking the opportunity to do a number of long aspirational jobs once I needed to replace the clutch release bearing. One of the jobs is an engine bay tidy, including the rather messy wiring hence my interest.

I know that this doesn't help you much at this point, but anyone else wanting to replicate a diagram or create a new diagram, I would suggest using software made for this purpose. I use Scheme-it, a free to use, on line electronics program from DigiKey. https://www.smartdraw.com/wiring-diagram/

If I had found Smart Draw before I started, I would have used it instead. It's not free but the ease to create automotive diagrams makes it worth the monthly cost, at least it would for me. https://www.smartdraw.com/wiring-diagram/

Being able to export diagrams as a PDF is most useful. Here's an in progress example from Scheme-it.

Eric,

I had a look at your mark 2 diagram. All looks good, though the hazard wiring is still missing.

Andy.

I have added the missing wiring to the hazard lighting circuit and cleaned up the connection from the dizzy to the coil.
Sorry for all the versions. It is a work in progress, as they say.

Cheers,
Eric

As Monty Python would say: "And now for something completely different".

Here is a different style of diagram which some may find easier to look at and think through. Not concerned about where items are located in the car, just how one thing connects to another.

Have a look at this and let me know what you think of this.

Thanks,
Eric

Much better for me at least, because you can follow (usually) what is happening.

Though personally I would show what the inside connections of the various switches are to be able to "follow the electrons".

And you left out the actual starter motor.


Wiring diagrams which try to follow the layout of the actual wiring loom are unnecessary (ideal for the bloke actually building a loom on pegs on a board) but difficult to read for anyone else.. All you really need to know are where the ends of the cable are and (usually) what colour(s) are the cable.

~~~~~~

Later: Oh I see that you meant that your starter motor has been replaced by one with a built on solenoid.

I don't understand your Horn circuit, you show only one earth and that is through the horn button, so the HEAVY horn current would seem to go through the horn button, making the relay just a nuisance instead of a help.

Hello Bill,

Thanks for catching the problem with the horn circuit. I went back to my reference book ( Classic British Car Electrical Systems by Rick Astley) and found the correct circuit layout for the horns. They suggest running a separate wire from the fuse to energize the coil of the relay with the push switch on the other end of the coil.
The power comes through the horns and enters the relay then exits to ground. Check out the modification to my diagram. I also realized that I had forgotten to ground the two headlight relays the same way, so that is now fixed as well.

Thanks again for the input.

Eric

billwill wrote:Wiring diagrams which try to follow the layout of the actual wiring loom are unnecessary (ideal for the bloke actually building a loom on pegs on a board) but difficult to read for anyone else.. All you really need to know are where the ends of the cable are and (usually) what colour(s) are the cable.

.

Very true indeed! Many get caught up in the actual diagram that only ends in confusion. I have rewired many older cars and use two central points - a fused and unfused block - from where I take all circuits to the relevant switches and device and earth them appropriately so that each device pretty well has its own circuit such as one has in a house. OK, so I use more cable than necessary, but it is cheap and using modern thinwall cable, the loom is a mighty fraction of the size of the original. I have rewired my +2 incorporating a full EFI controller using thinwall and with the wires wrapped neatly away, one would be hard pushed to see the looms.

Sure it would be different if I were wiring up a run of several thousand cars and had to return a profit, and then yes, I would be jumping connections all over the place to save a few bucks on each car.

As for horns, outside of trucks, emergergency and specialist high end cars that used air horns, the standard Britsh car did not have a relay for the horn (what is the cost of a relay then? A shilling maybe. BMC had to make a million minis. Forget the relay and save £50k...) - 12V was fed to the horn/s on a purple wire, returned to the horn button that was earthed to the steering column when pushed. They were not fused as many a Mini owner will testufy when they removed their steering wheel for the then go fast badge of a wooden Mota Lita wheel when they let the centre wire fall into the steering column that resulted in horns blaring and panic (hands up how many were caught out with this... )

Bushwacker wrote:As Monty Python would say: "And now for something completely different".

Here is a different style of diagram which some may find easier to look at and think through. Not concerned about where items are located in the car, just how one thing connects to another.

Have a look at this and let me know what you think of this.

Thanks,
Eric

Lotus Elan wiring diagram pictoral style_022621.pdf

That is pretty good Eric. I confess to not following the earlier part of your post as conventional diagrams bore me no end, but as Billwill notes, one just needs to see where it all goes without having to trace a run all around a page. But you have gone a long way to obviate the nonsense.

I urge you to spend some more time and maybe change some of the wire colours to conform more with the convention of the day - but I appreciate that the convention did not mean much to Lotus...

I second the suggestion that you need to incorporate the switch and relay inner circuits to cater for those not using or cannot use the original switches. Another point [I am surprised most diagrams do not show] is the cable size on each circuit that is handy for someone replacing a length or even making up a new loom.

Hi Eric,

That looks good to me based on a quick skim.

One question: it looks like there is a 10A fuse to the ignition switch. I can't remember the internal wiring of the switch in the different positions (i.e. is radio off when cranking, etc.) but do you or anyone else know what the solenoid current draw is when cranking?

I have seen general references (i.e. not specific to the Elan) for it being as high as 10-15A but can't confirm this, and it could be this is for pre-engaged style starters with built in solenoids. I found one reference here https://lotusmarques.com/info/technical ... lion-guide to the Lucas solenoid being about 5A, but can't confirm.

Depending on the answer to this, how the ignition switch is wired, and whether I've read the diagram correctly you might end up with sidelights, solenoid, coil, radio(?), alternator field windings plus some other trivial stuff all through that 10A fuse, which is probably ok but maybe a bit tight if you were to end up cranking the engine for ages for example. If the wires from fuse to switch to solenoid are a decent size you can always bump the fuse size up if it pops without problem.

Cheers,

Will

A few general notes. Many of the things we are used to in modern cars are the result of economies of scale.
The desire to save pennies on the size of wires and the availability of cheap relays from China means they are frequently more complex than need be. This also allows automation of many functions which we don't care about

Having more fuses allows smaller wire throughout the car, and once you are paying for one fuseblock the incremental cost of a larger fuseblock is less than hundreds of feet of larger wire, to a large automaker

For us, we are buying wire by the spool, and are not making more than one car.

Eliminate the relays where not really needed and use a larger wire. Simplicity
The factory rocker switches have lasted in my car for more than 140k miles, so they are not a failure point in my mind
If you are using striped wire, sticking to the lucas colors is handy but a good wiring diagram such as you have is the tool you really need in the future
I wonder if an oil pressure switch is just as effective as a rollover switch, perhaps easier to implement? maybe not