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Discussion Starter #1
I am so used to just turning off the ignition and the lights going off on my other vehicles, that I miss it on the R170. I prefer to drive with lights on, even during the day, and would like to know if anyone has come up with a way to have the lights correspond to the ignition switch.
Yes I can just turn it off and on, but it would be much nicer to update the lights to a system that is more current.
I would think, that if I can isolate the main power of the light switch and relocate the connection to an ignition prompted lead, it should work.
Any suggestions?
 

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Super Moderator UK 2002 SLK320 Blue
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I'm also used to that feature on my BMW and I do miss it on the SLK. I've not seen an after-market kit to do this but I would have thought it not too hard to do if you have the right relays and the right means of re-wiring the switch.

Thoughts anyone?
 

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Premium Member 2008 SLK200
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Hi
Good day.

It is actually quite simple if you want the headlights to be ON when ignition is ON
and headlights to be OFF when ignition is OFF.

But you do must have some simple basic of electric & relays, no big deal if you don't.

Rule of thumb: Never never tap off power supply from ignition switch to power headlight or any electric devices.
It could and or would overload the ignition switch.


Get a BOSCH relay.
4 terminals type. ( no need to use 5 terminal' type)
All terminals have a number > 85, 86, 87, & 30
( 5 terminals' relay has 87a)

route (wire) a power supply from any fuse (in the fuse box) that is ON (with 12 volt supply) when ignition is ON to the terminal (86)
route a wire from the terminal 85 to the car' body for earth (-ve)

route a heavy gauge wire from the +ve terminal of the battery to terminal (30).
Must have a line fuse, as near as possible to the battery for safety reason.

route a wire from the terminal (87) to the headlight.

That's all to it.

Thank you & have a nice day
 

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Super Moderator UK 2002 SLK320 Blue
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Knowledge is a wonderful thing
It certainly is. :wink:

I may adapt Hui Sweetcheong's approach and make the lights semi-automatic with some circuitry (Arduino or similar) to sense darker conditions and switch the relay at that time. That way we'll have automatic lights rather than just lights that come on with the ignition.

Now if I could also do the same with the windscreen wipers...... :nerd::nerd::nerd:
 

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Premium Member 2008 SLK200
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It certainly is. :wink:

I may adapt Hui Sweetcheong's approach and make the lights semi-automatic with some circuitry (Arduino or similar) to sense darker conditions and switch the relay at that time. That way we'll have automatic lights rather than just lights that come on with the ignition.

Now if I could also do the same with the windscreen wipers...... :nerd::nerd::nerd:
Hi
Good day.

Good idea to incorporate a light sensor in the system to auto switch on headlight when dark.

All you need is to look for a 12 volt DC light sensor & connect it in series to the power supply of the relay. (depending on the circuitry)

There a plenty of light sensors that I know of but they are AC110 or 220 > night light that you plug onto the wall socket.
If only you can convert it to 12 volt DC.
Or maybe there are off-the-shelf 12volt DC light sensor??

Thank you & have a nice day.
 

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Premium Member 2008 SLK200
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Super Moderator UK 2002 SLK320 Blue
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Super Moderator UK 2002 SLK320 Blue
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We may have to play with the circuit to make sure it has enough hysteresis to not switch on/off/on too quickly and that should be good.

Hah! I'll add that to my list of winter projects! :nerd:
 

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Premium Member 2008 SLK200
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Hi
good day.

The link you gave is a good device.
It is also stable as it has incorporated the stability' function to prevent the light from flickering.

Also the photo cell is route able with an extension wire.


Thank you & have a nice day
 

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Super Moderator UK 2002 SLK320 Blue
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Hi

Judging by the journey today I think I may be looking at this modification sooner than the winter. Maybe next week, in fact. Lots of cross country driving through forests and woods meant i was switching my lights on and off a lot and made me think through this modification.
 

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Super Moderator UK 2002 SLK320 Blue
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What about when driving where there are streetlights far apart? Will this device cause the headlights to go off and on repeatedly?
I think two answers here:

  • There wouldn't be enough change in light to trigger that.
  • You can still turn the headlights 'on' using the switch at night.
I've two other cars that have automatic lights so I was planning to do some experiments with the circuit and an LED while letting someone else drive around to make sure the module does what it should. There is quite a detailed explanation on the web page regarding delays and adjustments so we should be good.
 

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Hi
Good day.

This is the link to the light sensor & cheap & good.

AC DC 12V 10A Auto ON OFF Photocell Street Light Photoswitch Sensor Switch MY | eBay

If I am not mistaken, this sensor can be adjustable but preferably not because it is factory adjusted.
Any tempering with the fine adjustment screw might damage it unless you know how.

Thank you & have a nice day



I'm in the United States and it says this item is not available for shipment to the US. Not sure why. I still want to do the mod.
 

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Ok so I finally got to do this auto light off conversion on my 1999 slk 230 and it turn out very easy so I took the headlight switch off ( lots of instruction on how to remove the light switch in the forum) and found two connectors the first one ( no need to remove the second one) has three wires two large one and a small wire the two wire that concern us here is the big red and the big white with red strip the big red is the constant power which when removed kills the power to all the light and the white is accessory power which I used to trigger my relay (see attached picture). I use 70 AMP 12V relay I had laying around I bought from Digi-key years ago. Now if the switch is on the light will go off once the ignition switch is off no more worrying about leaving the light on and just add daylight running lights.
 

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