weird sound + brighter and dimmer light!?!?

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New Member
Jun 8, 2003
W202 C280, E46 320i
hi guys!!
recently my 1994 C280 has a kinda weird thing...
i found that the interior light system of my car goes dimmer then back to brighter then dimmer... again and again and once this happen, i can hear some "electric motor" sound from the trunk. somewhere around the rear right hand side. once the sound on, the light will be dimmer but once it turns off, the light will be normal "brighter".
other strange thing is that... this situation is not always happen. but i can tell when it will happen!!!!
i can sure that it's NOT the CD changer's problem.
can someone share your idea about that???
Stand outside the the trunk of the car with the car unlocked.

Press the unlock on your remote. Is that the wirring sound you hear?

The interior light dims when either a the pre-set time passes or the car is locked.

It sounds like perhaps you have either a faulty door/boot pin switch or perhaps a central locking fault to diagnose.
Thanks for reply!!!!

i'll try to check it out.

let me say it a bit more in detail...

the doors are unlock.
i stand outside the trunk and the trunk lid is open.
the light inside the trunk and so does the interior light go dimmer. (feels like "not enough battery") when the weird sound happen.
then the sound stop and the brightness of the lights back to normal.
2 seconds later, this happens again and again and again...

but sometimes it's OK!!!! no such a thing!!!
really needs someone help!!!
It does sound like the comfort module is operating when it shouldn't be and drawing current.

You may have a leaking vacuum pipe somewhere causing the module to over-run.
i'm sorry!!
would U mind to tell me what is "comfort module" ?
Originally posted by aroppi
i'm sorry!!
would U mind to tell me what is "comfort module" ?

I'm sure Dieselman will expand, but I I think it is just the control unit that looks after the interior lighting and dimming etc. Nothing more than that.
OIC!! thanks!!!

would it be possible to find the source of leaking?

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