I've often wondered why MB didn't put footwell lighting in the R170 SLK. A simple addition would've added a touch of class on an already classy auto. Anyhow, adding footwell lighting doesn't look to be a difficult job and there are a few people who have written up their exploits in this area on this forum, typically using a short length of 12V LED tape stuck to the top of the footwell / bottom of the dash.
So why the need for another version?
Well, I think the LED strip idea looks a little Heath Robinson if I'm honest - there are cables to hide and the glue on these tapes can sometimes weaken when it gets too warm and the LED tape will then sag or fall off - messy! Also the panels these are stuck to are removable and unless connectors have been used you will be restricted when you come to replace (for example) the cabin filter. So I looked at the project slightly differently to avoid these pitfalls and this is what I came up with:
First of all I took photographs of the underside of the dash so I could see what I was working with:
Concentrating on the passengers' side those holes would lend themselves to supporting a panel-mount LED housing if there was enough depth above - and this would mean minimum intrusion into the footwell and all cabling above that panel - a win/win for the passenger side (assuming you could find a suitable lamp).
The drivers' side looks a bit harder. There are no holes available and without removing the panel I can't see an easy way to install the lamp on this side. Further, I am loath to have anything below the panel in case it comes adrift when driving - not good for safety! I could drill a hole in the panel - but I'd have to then be sure any cables I install do not foul the steering mechanism above the panel.
Then I noticed the ventilation panel and I am now thinking if I can utilise this to house the lamp for the drivers' footwell.
Drivers - air vent.jpg
For the moment though let's concentrate on the passenger footwell. The holes in the panel measure 15mm across. And, as it happens, on eBay there are a large number of cheap 'DRL' type LEDs of various claimed powers and brightness known as 'Eagle Eye LEDs'. These fix with a bolt into a 12mm hole so they would be perfect in the panel above. The only thing I needed to add was a washer to help hold the lamp in place.
Anyhow. I purchased some lamps on eBay
to see if they were suitable. I'd already read some reviews that criticised the light output as 'too low' so I knew the 'cheap' quality of these units would make them more suitable here. Once they arrived I tested the current draw of one of them. This turned out to be around 80mA, indicating that the LED was a 1W unit. Perfect. Once lit, however, the light pattern looked poor:
But, as the lamp lens was plastic, a couple of minutes with some emery paper and the light pattern was transformed into this, which was much better!
Now the next stage is to plan how you want the lamp to work in the car. As you probably know, the dome lights turn on when the doors are opened or when the switch on the dome light is activated. On the circuit diagram below the lamps are in E15/1 and are fed from a permanent +12V on pin 4 (Red/Grey cable). They are switched on when either the Blue/Brown cable (pin 3) is taken to 0V (doors opening) or when the switch connects the lamps to ground (brown cable on pin 1).
Your choices are therefore:
- If you want the footwell lighting to come on just when the door opens then you need to connect the footwell lamps across E15/1 pins 4 and 3
- If you want the footwell lighting to come on whenever the dome lamps come on then you need to connect the footwell lamps across E15/1 pins 4 and 1
I chose the latter option reasoning that you may want footwell lighting at night without having to opening the door.
At this point we're in a position to carry out the installation (see following post). I'll include a list of what's needed in this post too.