W140
1993 300SD

When I hit the switch in overhead dome light unit to turn on the rear interior lights, only the 1 center light turns on. The 2 side reading lamps do not. These 2 side reading lamps do turn on though when the rear doors are opened or the button is pressed on them.

I know for a fact these 2 reading lights should turn on when the switch is flicked, as I saw it work in another W140. I even took the switch out from a working W140, but it did not fix it.

The only fuse I found for the rear lights was in the trunk.

Anyone have insight on whether a relay is the cause or know where the wires from the 2 readings lights conect to.

hmmmm, i do not think the rear reading lights should turn on from the front. Maybe when you saw it work on another w140 the rear doors WERE open somewhat. So when the switch was flicked to "door open" mode the lights turned on.

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85 190E 2.3(SOLD)
86 230E (-->300D)
87 300D (-->300TD)
68 250S w/ a 615 and manual tranny (RIP)
87 300TD (SOLD)
95 S280 "The KRAKEN" (Turbo 2.9 602 transplant)

Thats how my W126 is also. I think its normal. But on a older W126, the reading lights were full manual only.

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

is it possible to re-wire the reading lights to come on with a rear door opening?
would separate pin switches be required ?
thanks

You're right. I had a chance to check a 1995 W140 and it works exactly like my 1993 with only the centre rear dome light iluminating when the rear doors are opened. Meanwhile the 1992 W140 I checked has all 3 lights come on.

I pulled the centre rear dome light on my 1993 and the 1992, this was the observation:
1993 2 prong connection on light
1992 3 prong connection on light

I will venture a guess the prong difference has something to do with it, but since its designed to only iluminate the centre rear dome light after 1992, there must be a reason behind it and therefore nothing is wrong with mine.

Ya, prob wire a hot from center light to each reading light. Would be easy to do that way. I think a diode would be needed in each lead to prevent each reading light from turning on the center and opposite reading light.

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