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Light cluster - Bulb identification

G

Gebbly

Member
Hersham, Surrey
[caveat: I am working on the assumption that the Z4M and Z4 share the same rear light cluster. If this is wrong please let me know and I will try and get the posting moved to the M section of the forum]

For a wiring project I am working on with my Z4MC I am trying to figure out what each of the wires from the car into the rear light fitting are. I have established which wire is negative/ground. I have a DC power supply and an open ended connector block so I can provide power to each of the wires into the light fitting individually and watch which light comes on in the cluster. Each wire into the light fitting, when given power, is turning on a different section of the light cluster. Using the cars controls and trial and error I can figure out what some but not all of the bulbs in the light cluster are.

Given the sketch of the rear left light cluster below you can see I have identified some but not all of the light cluster sections. Could someone tell me what sections labelled B and D are please? I am guessing one should be the rear fog light? I have tried the "rear fog light" button in the cabin but dont see any noticeable difference in the cluster.

rearLeftLightCluster.jpg
 
I’m sure B would be fog light on lhd vehicles.
On RHD is should be fog iirc.
Easy to check go and still all your light on a press fog lights
 
Thanks for the responses. My Z4MC is a RHD in case that effects things. Looking at the wiring there are 6 wires in the connector going into the light fitting. One of those is gnd/-ve so there are only 5 wires available to provide a positive signal to bulbs (and 6 sections of the light fitting). I have used my DC power supply to send power to each wire in turn and found which wire powers on which bulb. So I now have a map of car controls to bulbs and also wires of the connector to bulbs.

Findings:
I have added to my diagram the connector that goes into the light fitting. It is drawn looking down on the right hand side connector as you look into the boot. The wires on the connector have been numbered and so have the light fitting segments.

I can now see that none of the wires gives power to segment D so I think [ref]markplant[/ref] is correct that D is purely a reflector, thanks.
Segment B on the right hand side light fitting lights up when I turn on the rear fog light from the dashboard. So [ref]j3nks79[/ref] was correct there, thank you.
However, with the fogs turned on, segment B on the left hand side light cluster does not come on. Should a Z4MC have a rear fog light on both sides? If so I need to figure out if I have a wiring or bulb problem.

rearLightWiring.jpg
 
j3nks79 said:
No only has fog light on one side.
Click to expand...
Brilliant, thanks [ref]j3nks79[/ref], that means the wiring is all working as intended. I can continue with my project :)
 
Scooba_Steve said:
But they will both illuminate for the brake force display.
Click to expand...
Thanks for the extra tip [ref]Scooba_Steve[/ref].

I havent checked yet but I'm wondering if there is a bulb in the fog segment in the left hand light fitting even though it doesnt come on. It would be fairly simple to run cable from the right hand fog wire over to the left and then have 2 rear fog lights. Or does anyone know any reasons not to do this? Are there any regulations regarding a second rear fog light?
 
Gebbly said:
Scooba_Steve said:
But they will both illuminate for the brake force display.
Click to expand...
Thanks for the extra tip [ref]Scooba_Steve[/ref].

I havent checked yet but I'm wondering if there is a bulb in the fog segment in the left hand light fitting even though it doesnt come on. It would be fairly simple to run cable from the right hand fog wire over to the left and then have 2 rear fog lights. Or does anyone know any reasons not to do this? Are there any regulations regarding a second rear fog light?
Click to expand...

There will be a bulb there already. It will be much easier to just code both bulbs to come on. If you do that I would suggest changing the brake force display to flashing, though I only managed to to get my third to do it rather than all 3.
 
Scooba_Steve said:
much easier to just code both bulbs to come on
Click to expand...
Oh thats a clever idea. I hadnt even considered coding as a possibility. Now I need to read up and coding and see what is possible. Thanks [ref]Scooba_Steve[/ref] :thumbsup:
 
Gebbly said:
Scooba_Steve said:
much easier to just code both bulbs to come on
Click to expand...
Oh thats a clever idea. I hadnt even considered coding as a possibility. Now I need to read up and coding and see what is possible. Thanks [ref]Scooba_Steve[/ref] :thumbsup:
Click to expand...
You’re welcome. Carly might be easier to use for trial and error but there might not be the option to do it. NCS is better for specific and custom options but a lot more difficult to figure out.
Ideally I wanted flashing BFD on all three brake lights without fogs as I think flashing gets the attention but fogs coming on isn’t going to tell the average joe I am braking hard. But I gave up trying as I could only get the third brake light to flash, though that’s good enough for me.

So it should defo be possible to enable both fogs, I just can’t say exactly how.
 
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