w123 Trunk light no power

[martureo]

Like the title says, I've got no power to my trunk light. I'm scratching my head over this and getting a bit frustrated.

Here's what I know now.

1. Continuity from ground wire at bulb to body
2. Ground connection is good
3. Switch is good
4. Continuity between switch and power wire where entering wiring loom at trunk firewall
5. Power good at 14 pin connector 1
6. Continuity between pin 1 and red wire entering beneath rear seat bench

The other problem is that the electrical wiring diagram in the Service Manual and the Electrical Manual both have the wire coming from the 14 pin connector pin 1 to the trunk switch as a Red/Yellow/White wire. There is no other connection from that wire between the connector and the switch, and there's no red wire on the 14 pin connector.

I can trace the Red/Yellow/White wire from the trunk switch to a larger loom at the trunk firewall. I can trace the red wire from pin 1 at the connector all the way along the floor to the rear bench seat. But I've got nothing between the two.

Here's what I'm looking at.



And here's the page from the Electrical Manual



Before I go tearing out the rear seat and poking more holes in the wiring, does anyone have a clue as to what's going on?

[Marshall Welch]

I’m not an expert, but I’m curious about what the voltage of the red wire would read along the wire located within the trunk (“boot” in UK English). As you probably know, it’s not difficult to remove the rear seat.