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Cannot manually turn on rear interior light on 156

818 Views 13 Replies 6 Participants Last post by  Binji
So, as the title says, when I open the doors all the lights illuminate, as they probably should, but I cannot turn them on when I'm driving for example. What could be the problem? Sometimes one of them does start working randomly...
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Discussion Starter · #3 ·
I know, but this is the problem, I cannot switch them on, nothing happens. The only time when pressing them does anything is when they're on by timer (when opening the doors for example).
 

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Discussion Starter · #5 ·
Yeah, I have to pull the headlining off (again!) anyway. It's wrong for the year and a bit tatty...
Anyway, this is what eLearn has to say:

They are switched on via a direct earth signal (permanently activated) or a signal coming from the integrated services control unit M40 .

Since the part with the integrated services control unit works I'm assuming I have to get an earth on one of the pins which should be easy enough? The wiring runs pretty close to where I was grinding the floor due to rust around one of the flaps so it is possible I've disturbed something there...
 

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Discussion Starter · #12 ·
Well, got the headlining off so I tried fixing the lights but I'm thoroughly confused now.
I measured the input with multimeter and it seems to be like this

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That would mean the switch inside the light should switch between left and right connection so that when the door is closed it would switch to the right earth and light up! But when I measured the resistance there only seems to be a connection between middle and left or nothing at all. I also removed the switch and same thing. There is never any connection between middle and right pin!

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Are all my switches bad? I would appreciate if someone with working lights or some more knowledge can help me clarify this :)
 

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Discussion Starter · #14 ·
Actually the permanent earth works fine. There is always 12V between middle and right terminal, there is just never a connection between the two in the lamp, that's why I suspect the switch inside the lamp. If the lamp was to light up with the doors open when the left terminal gets 12V that would mean the permanent earth would have to be the middle (common) terminal. Which is not... Left terminal actually becomes earth and when it deactivates it's likely an open circuit.

Position for the doors open light
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This should then be the path to light up during driving...

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If I bridge the terminals it works...

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But that would mean not one of the switches out of the five I've tested, works...
 
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