How to find a particular wire(illumination)?

**ghostdunks** · 03-30-2007

This may be a really basic question but I can't figure it out. I've chucked this same question onto benzworld and slkworld in the hope that someone with some technical ability can help me

I'm putting a new radio headunit into my Australian 2005 SLK280, and I've got an adapter for the stock Mercedes wiring harness to ISO, so I can plug it pretty much straight in. The harness itself is missing 2 wires, the IGNITION and the ILLUMINATION. From what I understand, this is because these signals are in the CAN-BUS, and they wouldn't come in a stock standard harness to ISO converter, and I'll need a CAN-BUS device to interpret these signals and convert. I have found such a device from Dietz but the item itself was prohibitively expensive so I thought, stuff that, I'll just wire it up myself, which is where my problem comes in. The IGNITION is not a problem as I can either tap into the cigarette lighter socket and get the power there, OR do as noregret4life suggested, and use a Add-a-circuit on the CIG fuse in the engine compartment and run a separate switched IGNITION wire back. I'll probably go for the Add-a-circuit route as this means I don't have to cut or tap into any stock wires.

The ILLUMINATION is a bit tougher, so I'm asking for advice. I'm thinking the easiest place to get this is to tap into the headlights wire and I was looking at the lighting fascia(the one where you select lights off, lights auto, lights on, foglights, etc..). I've already tapped into the power wire for my piecha module as this was the recommended way for a RHD install of the piecha, so I've seen the wiring loom. Now the question would be, how do I find the right wire to tap??

When going through the 46 page on the install of the Piecha module, someone suggested a way to find the right wire for power(which I was thinking of trying to use while finding the headlights wire). This way was to stick a pin into a possible wire, and then use a voltmeter/multimeter to probe the pin to see how much voltage was flowing through it. Is this the right/only way to figure out what wires do what without actually stripping the wire?

DansSlk · 03-30-2007

The light switch does not directly connect to the headlamps/taillamps those signals travel on CANBUS to the Front and Rear SAM's you would need to tap one of the wires to the lights themselves

DansSlk · 03-30-2007

Had another idea if you have the comfort lighting on the car you could wire it up to the footwell lights since they will operate on the dim setting all the time when the ignition is on and the light sensor says its dark/you have the lights on.

**ghostdunks** · 04-02-2007

thanks for the headsup on the lightswitch being on the CANBUS.

someone on benzworld mentioned that the illumination wire is available on the cigarette lighter, which I guess makes sense since I would assume that it would light up when the headlamps go on.. Then i realised of course that my car didn't come with the cigarette lighter in the dash(came with the bigger slide out tray instead of ashtray and cig lighter) :P Not sure if they'll have a loose wire hanging around somewhere in the dash waiting to be connected.

I do have the 12v outlet at the side of the passenger footwell, and not sure if that'll have the illumination wire in there since its not part of the dash(and doesn't need to light up)..although I do remember when I took the console apart to check the radio connections, I remember seeing 3 wires leading to that outlet. Assuming that one would be power and the other ground, I can only assume the other wire HAS to be illumination..

**ghostdunks** · 04-02-2007

have a slightly unrelated question here Dan(or whoever else).. as part of taking apart the dash using some documents, some of the steps mention putting the shifter in D or neutral or whatever.. Usually when I'm working on the car, I park it, put it in park, and turn ignition off, and take key out. Once its in Park, how do I put the shifter into another mode(say D) when the car is not turned on?

DansSlk · 04-02-2007

Quote:

Originally Posted by ghostdunks

thanks for the headsup on the lightswitch being on the CANBUS.

someone on benzworld mentioned that the illumination wire is available on the cigarette lighter, which I guess makes sense since I would assume that it would light up when the headlamps go on.. Then i realised of course that my car didn't come with the cigarette lighter in the dash(came with the bigger slide out tray instead of ashtray and cig lighter) :P Not sure if they'll have a loose wire hanging around somewhere in the dash waiting to be connected.

I do have the 12v outlet at the side of the passenger footwell, and not sure if that'll have the illumination wire in there since its not part of the dash(and doesn't need to light up)..although I do remember when I took the console apart to check the radio connections, I remember seeing 3 wires leading to that outlet. Assuming that one would be power and the other ground, I can only assume the other wire HAS to be illumination..

The 12 volt socket does not light up its on the same circuit as the diagnostic socket so the 3 wires are actually 2 split power in, power out and gnd.

The ciggy lighter does light but if you don't have it then the wire harness might terminate way back behind the dash out of access if its installed at all.

As far as i can see you have the footwell lights, the headlamps/taillamps or you can use the lights in one of the storage compartments.

DansSlk · 04-02-2007

Quote:

Originally Posted by ghostdunks

have a slightly unrelated question here Dan(or whoever else).. as part of taking apart the dash using some documents, some of the steps mention putting the shifter in D or neutral or whatever.. Usually when I'm working on the car, I park it, put it in park, and turn ignition off, and take key out. Once its in Park, how do I put the shifter into another mode(say D) when the car is not turned on?

Never put the shifter into D when working on the car put it into N with the E-Brake on.

To move the shifter you need they CAN-C to be online so the key needs to be in position 2 and then you move it like normal but don't move it about too much or you will find yourself not being about to put it back into park and the engine refusing to start.

**ghostdunks** · 04-03-2007

Quote:

Originally Posted by DansSlk

The 12 volt socket does not light up its on the same circuit as the diagnostic socket so the 3 wires are actually 2 split power in, power out and gnd.

The ciggy lighter does light but if you don't have it then the wire harness might terminate way back behind the dash out of access if its installed at all.

As far as i can see you have the footwell lights, the headlamps/taillamps or you can use the lights in one of the storage compartments.

Actually, scratch that 3 wires memory, I saw another thread where someone else had a picture of the wires going into the 12V socket

http://www.slkworld.com/general-modi...ccess-acc.html

Actually looks like theres 4 wires going into it...however like Dan just mentioned, its probably 2 power in and 2 power out maybe? When I get the car back, I'll test them to see.. I'm not expecting any of them to be illumination, but can hope

Yeah, I reckon the wire harness for the ciggy lighter is probably hidden away somewhere if I even have it..

Seeing as you mention other possible places to get illumination, I was thinking about somewhere else on the main console..maybe connected to the climate control switches? I remember them lighting up when headlights are turned on, but I'm not sure.

DansSlk · 04-03-2007

The thing is most of the systems only have basic connections - 12V, GND, CAN +, CAN - and direct connections to the sub systems they operate.

So the climate control unit gets a signal from CAN BUS saying the light level has dropped below X amount / The lights have been activated manually it then says OK gotta fire up the LED's.

It works that way to keep the amount of wires needed down since we are talking about miles and miles of wire in total installed in the car's and that carries some serious weight.

I did think of one place the shifter unit position display lights up and it has 3 wires connected to it.

A white/yellow for connection to the transmission controller to set the mode, a brown wire that goes to ground and a blue wire that gets a 12V signal from the Driver SAM when the lights are on you could tap that wire if you needed.

Would that be OK?

**ghostdunks** · 04-04-2007

you really are a bundle of useful info, Dan

ok, scratch the climate control...but thumbs up on the shifter unit! That one looks like the one to tap then, sounds exactly like what I need...soon as I get the car back from the shop(in shop for varioroof issues), I'll pop that part out and have a looksee..if I can't find the harness for the cig lighter anywhere close, I'll just tap that blue wire. I've got to take the shifter unit out anyway, in order to get to the radio so thats not a big problem.

Thanks again for the advice, I'll give it a shot and report back.

**ghostdunks** · 05-07-2007

When I took the car apart, I had a look at the 12 volt socket anyway. As the middle wire was exactly the same colour(blue with a white strip) as the illumination one on the "shifter unit position display" that you recommended, I got my multimeter out and just checked out that wire. I measured just below 6v when illumination was on...so, similar to switched 12v power, but only half and when illumination's on? What could this be for? The other wires on that harness were ground, and a 12v switched power, so whats a 6v illumination wire for?

While I had the multimeter out, I checked out the illumination one on the shifter unit position display, and that one worked out fine..12v when illumination was on, so that was the one I tapped. Still interested in what that 6v wire's for though just out of curiosity

DansSlk · 05-07-2007

I honestly have no idea i cant trace it from anywhere it does not originate in the illumination lines coming from the SAM and it's not connected to any control unit so i am at a loss with it.

Not sure why it reads 6V everything i can think of just uses battery voltage

**Zeiser50** · 05-07-2007

Sometimes, the power is pulsed (square wave signal) in order to check if the bulb is burnt or not. As the pulse ratio is 50%, a voltmeter indicates 6v (and not 12v).
Don't know if it can helps.

DansSlk · 05-07-2007

The odd thing here is that the 12V socket does not have any form of illumination.

Only thing i can think of is it was originally planned and a wire was added to the harness for it then for whatever reason they decided no light in there and could not be bothered to remove the wire since its only pennies to leave it in and a **** load of money to remove it from the designs

**Zeiser50** · 05-07-2007

The bulb forecasted during the design has been probably killed by the "MB cost killer". ....

DansSlk · 05-07-2007

Exactly mate exactly.

Bet the price of the bulb is still on the MSRP tho

**ghostdunks** · 05-08-2007

hahahaa

I thought that maybe they use the same wiring harness to hook up both the cigarette lighter and the 12v socket on the side, and the socket on the side doesn't have the light, so it just doesn't use the wire, but if you got the ashtray package with the lighter, it would use the same connector and would then use the wire? Just theorizing.

**Zeiser50** · 05-08-2007

Less connectors model, harness is cheaper ...

Maybe also, on right side driving cars, the 12v socket goes on the left side. In this case, the connector used for cigarette lighter is used for the socket and the connector of the socket is used for the cigarette lighter ?

DansSlk · 05-08-2007

In the US the 12V socket and the Ciggy Lighter are on the same circuit but the illumination ring is different they split into a harness all of there own back behind the dash and then run to the Driver SAM.

In all other variants of the cars the 12V and Ciggy are on different fuses altogether running completely separate of each other and again the illumination ring is all on its own so it makes less sense in these cars to wire up for the sake of it there must have been a reason for it as some point that has probably since been deleted in the US cars it would make more sense to share a common harness.

I think a lot of it is that these cars share just about everything from the W211 so in some places there are dis-used connectors and wires leading to nowhere a good place to see this is the Central Gateway and the Rear SAM just take a look at them and see how many of the connections are not in use and you get a good idea of all the odds and end's in the SLK.

03-30-2007	#1 (permalink)
ghostdunks Elite SLK World Member Join Date: Feb 2007 Location: Melbourne, Australia Vehicle: SLK280 Posts: 211 Country: Thanks: 6 Thanked 4 Times in 3 Posts	How to find a particular wire(illumination)? This may be a really basic question but I can't figure it out. I've chucked this same question onto benzworld and slkworld in the hope that someone with some technical ability can help me I'm putting a new radio headunit into my Australian 2005 SLK280, and I've got an adapter for the stock Mercedes wiring harness to ISO, so I can plug it pretty much straight in. The harness itself is missing 2 wires, the IGNITION and the ILLUMINATION. From what I understand, this is because these signals are in the CAN-BUS, and they wouldn't come in a stock standard harness to ISO converter, and I'll need a CAN-BUS device to interpret these signals and convert. I have found such a device from Dietz but the item itself was prohibitively expensive so I thought, stuff that, I'll just wire it up myself, which is where my problem comes in. The IGNITION is not a problem as I can either tap into the cigarette lighter socket and get the power there, OR do as noregret4life suggested, and use a Add-a-circuit on the CIG fuse in the engine compartment and run a separate switched IGNITION wire back. I'll probably go for the Add-a-circuit route as this means I don't have to cut or tap into any stock wires. The ILLUMINATION is a bit tougher, so I'm asking for advice. I'm thinking the easiest place to get this is to tap into the headlights wire and I was looking at the lighting fascia(the one where you select lights off, lights auto, lights on, foglights, etc..). I've already tapped into the power wire for my piecha module as this was the recommended way for a RHD install of the piecha, so I've seen the wiring loom. Now the question would be, how do I find the right wire to tap?? When going through the 46 page on the install of the Piecha module, someone suggested a way to find the right wire for power(which I was thinking of trying to use while finding the headlights wire). This way was to stick a pin into a possible wire, and then use a voltmeter/multimeter to probe the pin to see how much voltage was flowing through it. Is this the right/only way to figure out what wires do what without actually stripping the wire?

03-30-2007	#2 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,752 Country: Thanks: 96 Thanked 221 Times in 173 Posts	The light switch does not directly connect to the headlamps/taillamps those signals travel on CANBUS to the Front and Rear SAM's you would need to tap one of the wires to the lights themselves __________________ One thing you will learn with German cars - If it's simple it ain't happening.

03-30-2007	#3 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,752 Country: Thanks: 96 Thanked 221 Times in 173 Posts	Had another idea if you have the comfort lighting on the car you could wire it up to the footwell lights since they will operate on the dim setting all the time when the ignition is on and the light sensor says its dark/you have the lights on. __________________ One thing you will learn with German cars - If it's simple it ain't happening.

04-03-2007	#9 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,752 Country: Thanks: 96 Thanked 221 Times in 173 Posts	The thing is most of the systems only have basic connections - 12V, GND, CAN +, CAN - and direct connections to the sub systems they operate. So the climate control unit gets a signal from CAN BUS saying the light level has dropped below X amount / The lights have been activated manually it then says OK gotta fire up the LED's. It works that way to keep the amount of wires needed down since we are talking about miles and miles of wire in total installed in the car's and that carries some serious weight. I did think of one place the shifter unit position display lights up and it has 3 wires connected to it. A white/yellow for connection to the transmission controller to set the mode, a brown wire that goes to ground and a blue wire that gets a 12V signal from the Driver SAM when the lights are on you could tap that wire if you needed. Would that be OK? __________________ One thing you will learn with German cars - If it's simple it ain't happening.

05-07-2007	#12 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,752 Country: Thanks: 96 Thanked 221 Times in 173 Posts	I honestly have no idea i cant trace it from anywhere it does not originate in the illumination lines coming from the SAM and it's not connected to any control unit so i am at a loss with it. Not sure why it reads 6V everything i can think of just uses battery voltage __________________ One thing you will learn with German cars - If it's simple it ain't happening.

04-02-2007	#4 (permalink)
ghostdunks Elite SLK World Member Join Date: Feb 2007 Location: Melbourne, Australia Vehicle: SLK280 Posts: 211 Country: Thanks: 6 Thanked 4 Times in 3 Posts	thanks for the headsup on the lightswitch being on the CANBUS. someone on benzworld mentioned that the illumination wire is available on the cigarette lighter, which I guess makes sense since I would assume that it would light up when the headlamps go on.. Then i realised of course that my car didn't come with the cigarette lighter in the dash(came with the bigger slide out tray instead of ashtray and cig lighter) :P Not sure if they'll have a loose wire hanging around somewhere in the dash waiting to be connected. I do have the 12v outlet at the side of the passenger footwell, and not sure if that'll have the illumination wire in there since its not part of the dash(and doesn't need to light up)..although I do remember when I took the console apart to check the radio connections, I remember seeing 3 wires leading to that outlet. Assuming that one would be power and the other ground, I can only assume the other wire HAS to be illumination..

04-02-2007	#5 (permalink)
ghostdunks Elite SLK World Member Join Date: Feb 2007 Location: Melbourne, Australia Vehicle: SLK280 Posts: 211 Country: Thanks: 6 Thanked 4 Times in 3 Posts	have a slightly unrelated question here Dan(or whoever else).. as part of taking apart the dash using some documents, some of the steps mention putting the shifter in D or neutral or whatever.. Usually when I'm working on the car, I park it, put it in park, and turn ignition off, and take key out. Once its in Park, how do I put the shifter into another mode(say D) when the car is not turned on?

04-04-2007	#10 (permalink)
ghostdunks Elite SLK World Member Join Date: Feb 2007 Location: Melbourne, Australia Vehicle: SLK280 Posts: 211 Country: Thanks: 6 Thanked 4 Times in 3 Posts	you really are a bundle of useful info, Dan ok, scratch the climate control...but thumbs up on the shifter unit! That one looks like the one to tap then, sounds exactly like what I need...soon as I get the car back from the shop(in shop for varioroof issues), I'll pop that part out and have a looksee..if I can't find the harness for the cig lighter anywhere close, I'll just tap that blue wire. I've got to take the shifter unit out anyway, in order to get to the radio so thats not a big problem. Thanks again for the advice, I'll give it a shot and report back.

05-07-2007	#11 (permalink)
ghostdunks Elite SLK World Member Join Date: Feb 2007 Location: Melbourne, Australia Vehicle: SLK280 Posts: 211 Country: Thanks: 6 Thanked 4 Times in 3 Posts	When I took the car apart, I had a look at the 12 volt socket anyway. As the middle wire was exactly the same colour(blue with a white strip) as the illumination one on the "shifter unit position display" that you recommended, I got my multimeter out and just checked out that wire. I measured just below 6v when illumination was on...so, similar to switched 12v power, but only half and when illumination's on? What could this be for? The other wires on that harness were ground, and a 12v switched power, so whats a 6v illumination wire for? While I had the multimeter out, I checked out the illumination one on the shifter unit position display, and that one worked out fine..12v when illumination was on, so that was the one I tapped. Still interested in what that 6v wire's for though just out of curiosity

05-07-2007	#13 (permalink)
Zeiser50 Elite SLK World Member Join Date: Mar 2007 Location: Paris Vehicle: SLK 55 AMG Other Toys: Bike : '84 Z1300-6 Posts: 506 Country: Thanks: 6 Thanked 18 Times in 14 Posts	Sometimes, the power is pulsed (square wave signal) in order to check if the bulb is burnt or not. As the pulse ratio is 50%, a voltmeter indicates 6v (and not 12v). Don't know if it can helps. __________________ To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts. ------Michel------ -SLK 55 AMG 2005-

05-07-2007	#14 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,752 Country: Thanks: 96 Thanked 221 Times in 173 Posts	The odd thing here is that the 12V socket does not have any form of illumination. Only thing i can think of is it was originally planned and a wire was added to the harness for it then for whatever reason they decided no light in there and could not be bothered to remove the wire since its only pennies to leave it in and a **** load of money to remove it from the designs __________________ One thing you will learn with German cars - If it's simple it ain't happening.

05-07-2007	#15 (permalink)
Zeiser50 Elite SLK World Member Join Date: Mar 2007 Location: Paris Vehicle: SLK 55 AMG Other Toys: Bike : '84 Z1300-6 Posts: 506 Country: Thanks: 6 Thanked 18 Times in 14 Posts	The bulb forecasted during the design has been probably killed by the "MB cost killer". .... __________________ To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts. ------Michel------ -SLK 55 AMG 2005-

05-07-2007	#16 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,752 Country: Thanks: 96 Thanked 221 Times in 173 Posts	Exactly mate exactly. Bet the price of the bulb is still on the MSRP tho __________________ One thing you will learn with German cars - If it's simple it ain't happening.

05-08-2007	#17 (permalink)
ghostdunks Elite SLK World Member Join Date: Feb 2007 Location: Melbourne, Australia Vehicle: SLK280 Posts: 211 Country: Thanks: 6 Thanked 4 Times in 3 Posts	hahahaa I thought that maybe they use the same wiring harness to hook up both the cigarette lighter and the 12v socket on the side, and the socket on the side doesn't have the light, so it just doesn't use the wire, but if you got the ashtray package with the lighter, it would use the same connector and would then use the wire? Just theorizing.

05-08-2007	#18 (permalink)
Zeiser50 Elite SLK World Member Join Date: Mar 2007 Location: Paris Vehicle: SLK 55 AMG Other Toys: Bike : '84 Z1300-6 Posts: 506 Country: Thanks: 6 Thanked 18 Times in 14 Posts	Less connectors model, harness is cheaper ... Maybe also, on right side driving cars, the 12v socket goes on the left side. In this case, the connector used for cigarette lighter is used for the socket and the connector of the socket is used for the cigarette lighter ? __________________ To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts. ------Michel------ -SLK 55 AMG 2005-

05-08-2007	#19 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,752 Country: Thanks: 96 Thanked 221 Times in 173 Posts	In the US the 12V socket and the Ciggy Lighter are on the same circuit but the illumination ring is different they split into a harness all of there own back behind the dash and then run to the Driver SAM. In all other variants of the cars the 12V and Ciggy are on different fuses altogether running completely separate of each other and again the illumination ring is all on its own so it makes less sense in these cars to wire up for the sake of it there must have been a reason for it as some point that has probably since been deleted in the US cars it would make more sense to share a common harness. I think a lot of it is that these cars share just about everything from the W211 so in some places there are dis-used connectors and wires leading to nowhere a good place to see this is the Central Gateway and the Rear SAM just take a look at them and see how many of the connections are not in use and you get a good idea of all the odds and end's in the SLK. __________________ One thing you will learn with German cars - If it's simple it ain't happening.