Yet another narcissistic load of old cobblers that no-one will ever read.

Replacing the starter button on my Lotus Elise

My car has a natty looking start button on the dashboard.  Obviously it's much easier to use than turning the ignition key one step further!  And it saves weight.  Well it must somehow 'cos that's Lotus' prime motivation for most of their design decisions, right?

(Note - see update at bottom!)

Anyway, it's a nice, racy sort of button and it lights up and everything.  Or at least it did light up until the bulb went.  Why they chose to use an incandescent bulb in these days of cheap, near-enough-everlasting LEDs is beyond me.  Actually, no it isn't.  Blown bulbs get people back to the garage where we customers can be relieved of some more of that pesky hard-earned cash.  Anyway, I didn't relish the thought of forking out for a new Lotus switch or being able to source the right bulb and replace it so I thought I'd get a different starter button with an LED from eBay:

So here, in the greatest tradition of Blue Peter-style how-tos, is how I fitted it...

An online article I found provided a wiring diagram with wire colours and also the author's comments provided me with more reason to replace the original:

The thing to note from the wiring diagram is that there are four wires on the Lotus switch but there are only three terminals on the eBay item!  However, on the lotus wiring there are two (green) wires that both go live when the ignition is on - one for the bulb and one for the switch - and we only need one so the other can be taped up.

Anyway off with the panel.  To remove the panel, undo the two screws inside the cubby hole under the panel.

To remove the existing switch you need to obviously undo the plastic nut - but you also have to remove the rectangular switch body from the cylindrical assembly by pushing in the little tab.  Only then will the assembly come out through the hole.

It turns out that the eBay switch doesn't actually fit properly in the hole - the retaining nut has a flange on it whose diameter is smaller than the hole it's pressing against - so the switch will just fall out.  Bummer.  The old switch came with an aluminium spacer though - and this provides just the adapter I need for the nut to bear against.  Except it would if the thread went far enough along the barrel of the new switch to reach past the spacer, which is too wide.  I got round this by inverting the nut so the flange was pointing outwards and the body of the nut could go inside the spacer some way and access enough thread to get a good enough purchase:

When I was preparing the terminals for the new switch, I noticed the silver bezel starting to unscrew.  A primitive instinct from my childhood took me over and I could not resist unscrewing it all the way.  I used to love taking stuff apart when I was little and was usually utterly incapable of reassembling the item before parental vengeance descended.  Anyway, my childish instincts won over against my better judgement this time and before I knew it, there were tiny springs an contacts all over the place.  With adult dexterity, resourcefulness and patience however, I was able to effect a re-assembly using a dab of silicone grease to hold springs straight while I replaced the button and bezel.  I now know what the innards look like - but it wasn't worth it.  You should definitely skip this step.

Anyway, to make the connections, I severed the old switch from its connector with scissors, leaving enough wire on both halves so I could re-connect later if it all went horribly wrong.

For some reason known only to Lotus, the wires from the connector to the switch are all black except for one red wire whereas the colours on the main wiring loom are not.  They match up as follows:

Ref. Connection Wiring Loom colour Connector colour New switch terminal (number)
A Bulb feed green red not used
B Bulb ground black black 3
C To starter via immobiliser white + red black 2
D From ignition switch green black 1

I connected the severed wires to the new switch using crimped eyelet connectors.  You can secure bare wires under the screw terminals of the new switch but I opted for a safer connection.  I was going to solder the wires into the eyelets - but in the end I couldn't be arsed so I just crimped them:

I taped the terminals up after this - just in case.

And then I tried it out.  The light came on when I turned on the ignition - yayyy!  But when I pressed the button, nothing.  I got my multimeter out and that told me the switch was fine and groovy.  And then it came to me: the immobiliser!  So I clicked that off with the alarm remote and bingo!

Here is the result:

I was not much of a fan of the original button - despite it's excitingly turned aluminium parts, it still seemed a bit plasticky.  However, I'm not 100% convinced this button is much of an improvement!  It looks a bit cheap (well, it was) and that light is very bright.  I could put an in-line resistor in to dim it a bit, I suppose.

Anyway, the jury is still out...



Turns out the 'bulb' in the original switch is an LED!  And it's blown.  Shows you what I know.

I'm going to see if I can figure out what bulb is the correct replacement.  My plan B is to dim the LED in the new button - but it may not be a simple as reducing the voltage because LEDs have a minimum forward voltage below which they just don't work.  The usual way to dim an LED is by turning it off for a short period and back on - but really fast so the eye doesn't notice. I could probably rig that sort of thing up (Arduino board?) but that's far too much trouble.  More later...


If you try any of this yourself and blow up your car, yourself or incur any other undesirable outcome as a result of this folly then it's your own daft fault for following instructions from the webpage of some idiot you've never met - and not mine!  I'm not an expert and don't profess to be.  Enjoy! :o)