Cigar lighter wiring

[John Larkin]

I am puzzled by the wiring for the cigar lighter in my S3SE Elan. I have summarised the Lotus wiring diagram in the attached sketch. The cigar lighter is shown as having three cables connected to it --- an earth connection, a connection to the panel lamp, and a connection to the fuseboard. A supply to the horn is taken off from that same fuseboard connection. A white/purple cable is connected to the other side of that fuse, and this connects to terminal 4 on the ignition switch. That white/purple cable is much smaller in size than the purple cable connecting the cigar lighter and the fuseboard.

Position 4 on the ignition switch is the auxillary position, and is also connected to the radio when fitted.

If the cigar lighter receives power from terminal 4 on the ignition switch this would mean that it would not work unless the key was in that position, and neither would the horn. So I suspect that the purple cable is delivering a power supply to the fuseboard, and from there on to the horn (unfused) and also (fused) to terminal 4 of the ignition switch. If this is correct then how does the power supply get TO the cigar lighter? Is it from the panel lamp connection?

My car is being re-wired right now and the wiring is not complete, so I can't check.

John Larkin.

[alan71]

In the 'aux' position only 4 is live, in the 'ignition on' position both 2 and 4 are live.
The numbers are confusing, they go 4, 2, 3 - aux, ign, start.

Alan.

[stugilmour]

John, might be helpful you look over one of the standardized Lucas wire colour diagrams a bit to be sure of the function of the various wire colours. Just in process of re-wiring my Plus 2; the specifics of your car might be slightly different, or things could have been changed around by a previous owner, but generally I found the Lotus wiring on my car to follow pretty closely to the standard. Anyway, found it best to get the wire colours over to standard in most cases; this might be what you are doing with your re-wire already?

Haven't looked specifically at the diagram for your model, so following are just general comments that I hope help. Here is a link to one of the colour diagrams I mean, there are several others available with a google search of "Lucas wire colour". I thought there was one of these on Lotuselan.net, but I can't find the exact link right now.

http://www.mgexperience.net/article/lucas-colours.html

A white/purple cable is connected to the other side of that fuse, and this connects to terminal 4 on the ignition switch. That white/purple cable is much smaller in size than the purple cable connecting the cigar lighter and the fuseboard.

I am not sure of this one; make sure you have it traced correctly. Generally the supply side of the fuse will be:
- Brown or Brown/White for the "hot at all times" fuse (purple output wires) and
- White for the hot in run/start/accessory fuse (green output wires)

As it is potentially a non-standard wire colour, a bit suspicious of what it does. Looking at the standard colour chart, begs question "do you have an electric fuel pump added to your car?"

So I suspect that the purple cable is delivering a power supply to the fuseboard, and from there on to the horn (unfused) and also (fused) to terminal 4 of the ignition switch. If this is correct then how does the power supply get TO the cigar lighter?

I think you have it back to front in your thinking on this one. Purple is standard colour for "Hot at all times, fused". It is essentially the fused power supply to the devises such as horn, cigar lighter, etc. that run even without the key inserted. It takes the power from the fuse to the devise.

Is it from the panel lamp connection?

No. The panel light circuit is completely separate. The Red/White wire is for the lamp within the cigar lighter housing, and is controlled by the panel light and side light switches. These circuits are supplied separately at the relevant switches by Purple, "Hot at all time, fused".

HTH

[John Larkin]

Alan, I did not know that terminals 2 and 4 were live with the key in the ignition position --- it makes sense. Thanks!

Stu, I am re-wiring the car. I am using new looms from Susan Miller, and the colours correspond with the Lotus wiring diagram. My sketch is taken from the Lotus service manual and is also the way that I have wired up behind the dashboard. From what Alan said about power being supplied to the white/purple wire from the ignition switch it seems that this is the power supply for the cigar lighter, but I cannot understand why the cable out to the fuseboard is smaller than the cable bringing power back in to the cigar lighter --- it looks to be about half the capacity, but is about the same length. This difference in cable size is in the original Lotus loom as well as my new loom.

Anybody know what current a cigar lighter pulls?

[paddy]

Anybody know what current a cigar lighter pulls?

It's quite high, and the wiring should be rated for 15-20 amps. Other than the lighter itself, anyone can plug anything they like into it.

http://en.wikipedia.org/wiki/Cigar_lighter_receptacle

Paddy

[stugilmour]

Sorry John, I do not have the Elan Plus 0 service manual available. I will take a look in my Brooklands book to see if I can see the White/Purple you are referring to. Not trying to confuse the issue, which may be model specific.

Quick edit...

Yes John, I see the wire you mean in the S3 diagram in the Brooklands book. Agree this must be the power supply to your fuse, although this set-up is different than my car. If you are uncomfortable with the wire size, I would definitely up-size it, but it appears to only operate the horn and the cigar lighter. I guess they figured these are intermittent use at best, so not as big an issue with wire size?

What escapes me with the set-up though is that it appears the fuse is only hot with the key in the run, start, or accessory position, rather than hot at all times. i.e. the horn and cigar lighter won't work with the key on the off position. The purple fuse in the Plus 2 runs a bunch of other stuff, hence my confusion.

Man, that is one diabolical diagram to read, even with a magnifying glass!

Cheers & good luck with the re-wire.