I the interior light use to come on for a few seconds once I opened and closed the doors but now it only comes on when I switch it on above the mirror.
Any suggestions would be appreciated.

your swtches could all be flakey...I went through the same thing last year on my W116, they would work if you fiddles with it when doors were open...switches were like $5.00 each...cured my problem...

Try jiggling the door switch and see it they come on.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Model would help here, as many have a switch position feature that keeps the door lamps from coming on.. it is just you may have it set to this feature/setting . but I do not know for sure b/c you have not included a chassis/model .

thanks it is a 1984 300 TD chassis 123

Very Good.. you do have that feature, so I would look and see if the switch has different positions .. they usually can be felt as they click in to each setting. Try each setting and then open a door..
The feature is for those who do not want the interior lamps to come on when opening any door.

well I'd see the sense in that but it does it with all 4 doors not just one

Mine did it on all four doors as all 4 switches were equally flakey....

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

As Arthur says, there are three positions to that switch, always on, always off and on when the door opens.

Len

and if its on the right setting wiggle the switchs...........if even one comes on that way you found the problem.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

I have this same issue and I've heard that there are two relays attached to the back of the speedo cluster and this is the most prevalent problem. Does anyone know about this?