[UPDATE]
Found and fixed...
It was the white/red wire from the glass latch broken in the usual hinge location. Interestingly it's the only one broken on that hinge. I've had to repair wires in all other hinges but not this one.
Symptom...
- Boot open alarm when pulling away
- Rear wiper not working
- Interior light stays on
- boot lights go on and off when you open but cover latches do not trigger.

Fix...
- Yet another broken wire.
- White/red in main tailgate hinge of left hand side (as you look into the car from the rear).

Standard procedure for fix. Strip tailgate plastics, disconnect both boot catch wires and left hand cluster. Remove large rubber grommet wires emerge from, remove metal guides from hinge and then with wire diagonally across the window gap you can pull the wired into the car and patch the wire through the speaker hole. As usual, disconnect the battery DO NOT close the glass latch.

Diagnostic shows as "rear window open" when you read body control module. I was a bit confused as to how it was turning the lights on and off but looking at the WDS diagrams it looks like some of the catch wiring is shared with the main tailgate and some is specific. Certainly a bit strange and glad I found it to be "just" another broken wire.

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[original post follows]
Here's a strange one... I've had the usual tailgate hinge issues over the years. But this is a new one. Anyone got any ideas?
You get a tailgate open warning alarm on the dash.
Rear wiper does not come on.
Assumption being one of the two boot access close sensor wires are broken.
But.....
Open the main tailgate.
- Cover latches pop,
- boot lights come on
- tailgate close motor whirs.(just the final close bit, I don't have auto close).

Close main tailgate.
- motor whirs
- boot lights go out.
This would suggest main tailgate switch and wires are OK.

Open the glass access window.
- Cover latches don't pop.
- boot lights come on

Close glass access
- boot lights go off.
This would suggest glass access switch and wires are OK. but a bit strange about the access cover.

However in all cases
- rear wiper does not work
- Interior lights stay on
- Alarm does not set
- Dash tells me boot is open each time I pull away.

Any thoughts of where to start? I'll probably get into all the hinge wiring again but given the lights go on and off OK I am dubious it's anything quite so simple this time.

Also can someone confirm is having either of the tailgate accesses open will stop the wiper working or is it just when the main access is open?

 

Sounds like intermittent hinge wiring.

 

I'll be following you on this one because I have "issues" with my tailgate and am at this point Inclined to replace the port hydraulic lift with a gas tube.

 

Fixed. See update to top post.

 

Thanks for posting the fix. Good job tracking it down

 

Ditto on the thanks. I've been afraid to tackle this one and you make it sound so eeeeeazzzzy.

 

I've had my tailgate apart many times. First time is a bit daunting but gets simpler after that. just remember not to close the glass tailgate window unless you are sure you can get it open again. There is a little hole you can wiggle a spring-hook in to release it but not unless you can access the side of the lock housing. The principal is the same for all 4 routes.
1. Strip the boot plastics (easy) generate some cable slack (easy)
2. Disconnect battery earth wire
3. Put a pillow in the boot so you can lay down but keep your head raised up when doing the wiring, make sure you can get comfy.
4. Take off the metal guides that take the cables around the hinge (pain but easy- my black bits are now in the bin, silver bits still used)
5. Take out the roof speaker (cover unclips, 2x screws to take the big black housing off, wiggle and jiggle to get it out and then swear at the connector a lot)
6. Take off rubber cover that goes through the roof metal-work. (next size up torx to the one you used for the speakers)
7. Gently pull the slack you have generated into the speaker hole and look at how many wires are broken.
8. Fix wires... bit of wire + solder + heat-shrink + loom tape. Loom tape is the fabric tape that you see on the standard wiring. Does a better job than insulation tape as it does not get messy. Get it on ebay.
9. Move everything enough to make sure it all works. Plug battery back in, test, disconnect battery again.
10. Put everything back together
11. Reconnect battery
12. Repeat as necessary... Takes about 90 mins start to finish once you've done it the first time.

2 additional mods I've carried out.
1. Run a wire from the glass release solenoid to the red/white boot light area and tape it up. Route it inside the tailgate plastics so if/when the glass release goes wrong (button, wire etc) you can connect that wire to the live side of the boot light bulb to pop the glass.
2. Leave off the screws that sit under the small cover that covers the wiper drive. These are the only ones you would not be able to get to if the rear glass does not open.

 

Thanks again. I'll start looking for instructional videos as well.