W124 Estate Interior Lights

[MB250TD]

I would be grateful for advice. Car is a W124 250TD 1989. Interior light fault has recently developed. The rear interior lights now stay on after rear doors and tail gate are closed. The lights have to be turned off manually using the rocker dash switch to the central position. I usually have it in the down position, such that interior lights come on when rear doors or tailgate are opened. The contact push switches on the rear door pillars briefly dim the lights when manually pushed in, suggesting these are Ok. Is the fault perhaps in the tail gate motor assembly, where I assume there must be a pressure or contact switch for the interior lights, or could a break in the wire to the tail gate near the hinge cause this problem?
Any help/suggestion greatly appreciated before I start to dissect the tail gate!
Thanks
John

 

[whitenemesis]

Centre position for the rocker switch is usually the "auto" setting i.e. the lights come on and go off when opening and closing the doors.

I'm not sure, on a car your age, but the interior lights won't come on if it's not dark, so you could have the lights set on permanently?