Boot won't open - A4 Saloon 2008

[mattwales]

Hello all - first post - first Audi!

Bought a second hand 2008 A4 Saloon a few weeks ago. Recently the boot has stopped opening. It would occasionally open once in the morning by chance, then wouldn't open the rest of the day. Now it's shut shut shut, no budging.

I used to use the 'hold the centre button on fob' method of auto-popping the boot open. I have tried the button on the drivers door, i've tried unlocking car then using the microswitch handle on the boot itself, but nothing is opening it. I don't know if the lock is jammed, or the mechanism to open it has failed - I understand these are all in one unit.

I've read about a 'valet mode' - my model doesn't have this as far as I'm aware - nothing in the glovebox anyway...

I've clambered into the boot after pulling the back seats down and found the emergency release - that didn't really budge it either before the plastic bit dislodged anyway... While in the boot I was pressing buttons on the remote I couldn't hear any clicking / whirring / noise from the boot latch at all.

This topic comes up a lot for the earlier A4's but not seen any solutions for this for the B8 model...

My question I guess is - should I replace the boot lock mechanism? (Provided I can force the "emergency release" to open) Or does this sound more like a control module fail? A Software issue?

Many thanks in advance for any help - I'd really like to use my big boot! (Main reason from upgrading the Golf!)

-Matt

Edit: When trying to activate the auto-boot-popping while clambered into the boot physically - I hear 4 clicks from what sounds like a control module in the O/S rear cubby hole bit. I think one is the electronic brake ecu, but it's the other one thats clicking I think - or it could be one of the relays in there... But anyway - I can confirm that the "signal" to open the boot is getting as far as that box/relay!

Edit 2: Finally got the manual release to work. The car "knows" when the boot is open because the boot light comes on and off as it should. Still no noise from the mechanism itself, but a definite four-click whenever the boot is closed / attempted to open from a control unit somewhere. So I'm pretty confident now that it's the boot mechanism. I've left the inner lining off for now and will browse the 'bay for a suitable replacement!

[Zenerdiode]

Hello Matt, you've waited a short while between joining and making your first post! :)
I was going to suggest the emergency release, but you've already found it. The four clicks are not directly trying to activate the tailgate, they are in fact the car 'waking up' and can be heard if flick the handbrake switch or something after it has been left a while. If you have any access to a fault code scanner (like VCDS) there would probably be a fault code stored.

it is most likely the lock solenoid, but remember it could be anything from a blown fuse, popped solenoid, wiring break, wiring short, the control module NFG (not functioning good :p) etc.

[mattwales]

Good evening Zenrdiode! Many thanks for your reply. Yes my join date and first post date have a ridiculously long time between them! I think the first time I registered was for a friends Skoda issue which never got resolved... Then I had a Golf for a bit, and now I'm in an Audi I feel I can be welcomed with open arms!

Thanks for the detailed technical info regarding the 4-click wake up. This is good to know. I'm pretty "technical" and these bits of info are quite interesting to me. Enjoy learning the inner workings of things!

I have a cheapy code reader, nothing stored on that, but have recently ordered a Ross-Tech "proper" cable now that I have a decent car worth coding.

When I took the inner lining off the other day mainly to get the boot-lock code, I sprayed a bit of WD40 in the mech and used the manual release a few times to get it lubricated. It's now opening every time - possibly as yesterday and today have been slightly warmer temperatures perhaps - or maybe the WD40 has done the trick. Either way I have another boot lock on it's way. I can rule out fuse / wiring I think as it's currently working every time. So either an ECU fail (NFG) - or the mechanism itself. Here's hoping it's the mech!

Anyway, thanks again for the reply, I'm looking forward to giving it a good clean (hopefully tomorrow if the Mrs doesn't demand too much of my time..!) and introducing myself more formally on these forums that I'm sure I'll be browsing much more in the future!

Regards,
Matt

[Boy]

Welcome.

Glad to gather that you have made progress with this fault.
One of the clicking noises you may have heard when crouched in the boot pressing buttons on your remote could have been the fuel cap lock solenoid which is,
as you would imagine, on the off-side just inside the fuel flap area!
Typically those fail, so it may not have been making any noise!

[mattwales]

Evening all,

So a bit of an update. Boot seemed to be opening absolutely fine after some WD40 lubed it up. But as I'd already bought a new (second hand) lock, I fitted it anyway. (It looked a LOT newer than the one currently on mine). Got it all changed over and the inner lining back onto the boot. All working great.

Also my VCDS cable arrived so have enabled the usual Needle Sweep, Graphic Parking display, mirror tilt on reverse, alarm chirps and looking at the coding required to do an LED rear light conversion!

Thanks all for your replies!

[Boy]

Good. Glad also to earn that you are now set to diagnose any further problems.