I'm almost embarrassed to ask this...
 

How do you open the back when the battery is dead or disconnected?

I disconnected the battery do work on the car, but could not figure out how to open the trunk again to re-connect the battery. :rolleyes:

You can't. Fold the back seat down and crawl in, re-connect the battery. Solved.

Yep, foolishly there is no mechanical override. Wave of the future!

Thank you guys, I was really feeling dumb...

It's not you, its them.

There are manual releases for both the lift gate and the tail gate - they are mentioned in the owners manual.

http://i68.tinypic.com/3166trb.jpg

http://i63.tinypic.com/97jmz5.jpg

You can also apply power at the B+ under the hood that's easier than crawling through the car.

Ditto...you can either do the manual unlock procedure outlined in the owners manual for the tail gate & lift gate...or connect a battery charger or jumper cables (using a donor vehicle) to the terminals in the engine bay. This should provide enough power to either use the tailgate release button on the lower dash or your remote fob trunk release button. And just in case you're not familiar with them...see the info below (also from the owners manual).


I recommend using the "special nut" located on the left fender for negative ground because you actually want this to work...using something else may not be truly grounded thus powering the tailgate won't work with power only to the B+ engine bay terminal. :)

This is great info, I've done this very same thing myself and once, while working on the engine heard the "thud" of the rear door when my wife thought she was being 'helpful'. :D

Thank you !!

I was going to ask next, what if the electrical part od the release latch failed...
But I got my answer before... Thanks !!

Definitely use the special nut. I didn't see mine until the 4th time I needed it (bad battery that tested good).

Oh yes this is a good way to do it.

I'm in this situation (on purpose) on my 2001 3.0i. In the middle of a head gasket (or more) repair, I have disconnected the battery in the back.

I found that hooking up either a battery charger, or a battery and charger in parallel to the B+ under the hood DID NOT WORK to let me open the rear hatch.

I really expected it to work, so when it did not, my son crawled in to do the manual release. And then I tied a string from the release thing to the driver's door seatbelt, so now I can just open the driver's door with the key, and then pull on the string to open the back.

I really don't know why the electrical method did not work, but it definitely did not work for me. With a weak battery, I have had it work. But with the battery disconnected, it did not. EDIT - also, yes, I used the "special nut."

What did you ground to? Did you attach the negative cable to the "special nut" on the left fender?

There is a real risk in applying power to the jump terminals when the battery is disconnected.

Where is the battery positive terminal? :dunno:

If you only disconnected the negative terminal, then there is no real chance of a problem. :thumbup:

If you have completely removed the battery or only removed the positive terminal, where is it sitting? If it is touching the chassis or the negative lead, Bad Things (tm) will happen if you apply a high current source to the jump terminals.... :yikes:

It’s not that hard to crawl in from the back seat. You’d have to do that for manual release anyway...

- If you don't want to crawl in, then use a spare battery or another car and jump the terminals under the hood.

I'm almost embarrassed to ask this...
 

B+ goes through the BST. If that is blown you won't be able to power anything from the B+/B- under the hood but you CAN power from the cig lighter port or the B+ on the trailer power connector (brilliant place to apply a battery tender)

SAGE advice from oldskewel and wpoll. Ensure no closed circuit before attaching a 1100A battery you will weld/melt anything in the path of conduction.

When in doubt check with Ω meter before you apply a high current source. If you're positive the battery terminals aren't shorted it's fair game to apply 12V across the jump terminals.

I'm curious why that didn't work when it didn't. I'm pretty sure the battery terminals shorts between high and low current sides so I would suspect unless BST blown this method should work.

(I have had cases where buttons didn't do as expected eg. Couldn't open door from exterior latch but the trunk button on the dash worked so that could have just been a computer hiccup..

One more food for thought since sometimes the battery is dead and a person is stuck outside the car.

B+ is directly attached to the starter solinoid under the car. I've heard of people jumping the car from there to get in if their key cylinder is hosed and they only get in with the key fob but the trailer power is much more elegant you just need to be careful with current lest you blow the fuse. (Eg use a charger set to 2a for example)

Just to make sure I'm clear here - that's what I did when my electrical opening failed. To answer + clarify, related to my experience (and it's still in this state, so I can go and test anything anyone wants):

- battery is in place in the back, with the negative terminal disconnected
- my first attempt was to attach my battery charger to the B+ port and the special nut in the engine bay. That did not work, but since I realized my battery charger may be a little too smart here to just apply 12V when there is no battery in the loop, I then ...
- connected a spare battery to the engine bay jump ports, and attached the battery charger to that spare battery to make sure it was at 12+V
- in this state, the key fob was completely non-op. And the hatch release button inside the truck did not work either.

On the other hand, with a battery that is low-voltage but still connected in the back, attaching a charger at the engine bay jump ports has been successful in making everything work.

I don't know what the answer is, and my "problem" might not apply to other E53's, but I'd at least recommend this as a warning to not count on it to work.

And basically one conclusion is that there is a difference between a dead battery that is still connected vs. a disconnected battery (at the negative terminal, if that matters).

Great feedback because as one would expect it "has to work" one diode to protect us from ourselves and no go.

Thanks for the additional info...it does paint a clearer picture.


It also makes me go back to what andrewwyn mentioned earlier about the BST (battery safety terminal). The engine bay components (starter/alternator/B+ terminal/etc) are connected to the rest of the vehicles electrical system through a postive B+ cable that runs back to the BST at the battery and the high amp fuses/rear fuses/glovebox fuses.



If the BST has failed or somehow become disconnected...trying to power from the engine bay won't work because none of the fuse boxes will receive power. If the BST is intact, even when the positive battery cable is removed from the car's battery...power is still being supplied to the high amp fuses, rear fuses, and glovebox fuses.

Good follow-up on the BST. It's still very curious the B+ jumper wouldn't run the tailgate, it would seem a fuse would have to be blown for that to be the case.