Greetings!

Hate to begin my posting here with something so mundane, but I gotta start somewhere...

Can't figure out the trunk light circuit on this vehicle. Here is what I have checked:

Fuse good (all interior lights work).
Bulbs in fixtures good.
Checked switch by removing it and jumping the terminals (no effect).
Checked power to each fixture. One hot, one not on each fixture.
I can get them to light if I drop the fixtures and ground the non-hot side to the body.

Soooooooooooo, what am I missing?!?!?!?

 

Memory. HAHAHAHA>

Turn ON the Park lights, maybe it works now, I think??????? mine did that, but its been a loooooong while, or was that the S2 Sedans, luv this age *****, NOT.

 

My guess is that the wire from the switch to ground is broken. Or the ground point where the wire attaches is dirty/loose/corroded

Cheers
DD

 

Doug correct. The boot lights need a good earth via the switch, could be the wire to the switch from the light, or from the switch to earth. On my car they are not dependent on the interior lights being on.

 

Thanks guys, 4 coffee's later and yes it was the S2 Daimler, and that fantastic mercury switch, oh boy.

 

Don't know how much different your 85 is from my 95 but here's a wiring diagram of the simple circuit. The trunk switch just completes the ground to the lights. One ground for two lights. Each light gets it own power leg from a common battery source fused, in the case of the 95 box "19" from left fuse panel , fuse 11. Hope this helps.

 

The boot lights are on Fuse #3 in the main fuse panel which is a different fuse to the interior lights. The power antenna is on the same fuse #3.

All the lighting is switched to ground. Make sure the ground connection from the boot switch is good, I would disconnect the grounds in the boot G9 in under where the boot light switch is and clean up the terminals and car body, re-install and put some body seam sealer on the connection to stop corrosion.

 

Thank you to all that took the time to respond. Upon further testing, I found the broken connection between the switch and the light (thanks for the tip).

Both trunk lights now functional!

My '85 XJS has the plunger type switch mounted in the upper left (if facing the open trunk) corner of the trunk lid opening, not the mercury type.

Now that I have that cleared up, I'm on to the next 17 or so electrical related faults I've found on this project so far...

DS

 

Just a thought: the boot light switch is notorious for not quite switching off when the boot closes, and thus draining the battery. If it is not in place, then glue a little rubber pad about 1/4 inch thick where the switch plunger contacts the boot lid. This will ensure no flat battery woes.

 

Ah yes, I had read that as well. Rubber cabinet bumper in place and verified that lights are off just before lid closes.

Thanks again for the responses!
DS

 

My car has a moulded plastic plate screwed to the boot lid where the switch contacts. If this plate is cracked or damaged the light stays on.

 

Mine appears to be tapped for just such a plate. Any idea on sourcing a replacement?

 

If you get the lights working and the plate is missing the boot lights will not switch off.

No ideas on sourcing a new one except eBay or buying a 3D printer and making a new one.