I have a device I can put inline with interior lights that will hold them on for an additional 10 seconds then fade slowly to off. Or if they are on and ignition is turned they fade without delay.

Lovely look

But I noticed on my 560 SEL that with the front doors open, only the fronts come on. Same for back. Which I think is normal. Is it? If

it is I can only wire up the front or back with what I have. Or I need to tie them up so when any door is open they all come on.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

I don't have a W126, mine is a W201..but should be the same.

The front & rear dome lights are on separate circuits. My model year did not have a 15sec delay like the later year models.

I used a feature from my aftermarket alarm to turn on the front & rear dome lights, when the alarm is turned off & doors unlocked.
The lights stay on for 1minute & turn off...enough time for me to walk to the car & get in. The lights would turn off immediately as soon as I turn on the ignition, even if the 1minute is not up yet. Also I used two diodes to isolate the front & rear circuits, to keep them separate like before.

Hmm, ok. I may have to try the diode thing.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

Front and rear entry and dome lights are activated only by the front or rear doors, respectably. This is purposeful: Someone getting into the back of the car doesn't dazzle the driver. The front dome light should have a delay when the ignition is not on. I think it's around 6 seconds?

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Yup. There is a delay but when parking in a dark garage its not very useful. And I have this little gizmo on hand anyway, so I may as well install it. Or at least try to figure out how to. I will start with the fronts only for now.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

Personally, I would not go messing with it....lol...if your interior lights work fine...leave them as is.

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1990 560 SEL- "Goldielocks"
1984 300SD TurboDiesel- "Ole' Blue"

I would be tempted to re-wire things a bit so that both dome lights come on when a front door is opened... Perhaps make it selectable with an additional dome light switch.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

That's exactly why I did it. I converted to high intensity leds as well, I unarm the car with remote from a distance & the whole area inside/outside is well lit.

The isolation diodes will keep the front & rear circuits separate. I.E.
1) open front door(s) - only front dome light comes on.
2) open rear door(s) - only rear dome light comes on.
3) unarm alarm - both front & rear dome light comes on for 1 minute.

Thats just it, they are on my list of "MB is an idiot" when it comes to this car. They are on for far to short a time.

I love this car, but for a 91 it sure is lacking in luxury features and updates. Then again, its a 1979 design!

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car