R129 Dead battery

[Agent Orange]

Hi

New to the forum and hit a problem with the SL320 R129 1999. Can anyone offer some advice?

Looks like the CTEK charge was inadvertently switched off as the battery is now dead and the alarm was pathetically chirping. Car is in my garage with door open to stop alarm.

Unfortunately the boot is shut and I'm unable to open, guessing insufficient power. Thankfully the charger is permanently connected to the battery so whilst I cannot get to the battery in the boot the charger is outside.

If I leave the doors open to prevent alarm going off am I good to charge the battery in situ ?

Thanks

 

[RichardF]

You can open the boot with the key, they're all manual. Yes you can charge in situ, as long as you have enough power in the battery fro the Ctek to recognise it's connected.

 

[ivan1983]

Details on how to open the boot are in this thread, it will probably feel quite stiff as it has probably never been used!
http://www.mbclub.co.uk/forums/electronics/205494-r129-electrics.html

 

[Agent Orange]

Thanks guys appreciate it. Never knew about position 3 on the boot lock!

 

[David404]

I've had good results with Ctek chargers recharging well depleted leisure batteries back to 100% charge. Just leave on charge for a day or two.

 

[Fintail66]

Details on how to open the boot are in this thread, it will probably feel quite stiff as it has probably never been used!
http://www.mbclub.co.uk/forums/electronics/205494-r129-electrics.html

Dear Ivan,

we disconnected the battery before changing the alternator on my 1994 SL320. Although I had left the trunk unlocked it is now not opening and we cannot reconnect the battery which is otherwise brand new, and fully charged. I do not think this can be opened manually by turning the key anti-clockwise. We have tried external current via the fud=se box but this only gives a very low current not enough to activate the central locking. The doors and central stowage compartments are all un locked. Any suggestions please.

 

[whitenemesis]

If the boot has a mechanical lock it can be opened with the key.
If the lock hasn't been used for a time it could be seized and need a release agent before the key will work.
Some model require a rather non-intuitive twisting sequence to unlock. Do you have a handbook for the car?

 

[Fintail66]

If the boot has a mechanical lock it can be opened with the key.
If the lock hasn't been used for a time it could be seized and need a release agent before the key will work.
Some model require a rather non-intuitive twisting sequence to unlock. Do you have a handbook for the car?

Thanks, , but I think it has a Hydraulic lock and the Owner's Manual (page 40) only gives the 4 positions: 1)Neutral, 2)anticlockwise to unlock, 3) clockwise to lock, and 4) further clockwise to leave the trunk locked when leaving with valet. not a sequence for un locking. I have however since been able to unlock. I connected the live wire from a heavy duty battery starter to the positive of fuse number 8, and negative to a car body earth. Then turned the ignition on to acc 2 position, and this activated the vacuum central locking.

 

[whitenemesis]

2)anticlockwise to unlock,

not a sequence for un locking.

So what's that then?

 

[Fintail66]

So what's that then?

Those are just the key positions of the boot opener. With my battery disconnected they had no impact on boot push button no matter what sequence I moved the key. Those positions only work if the battery is connected and has electrical power for activating the vacuum central locking. For the boot opener to function as a mechanical push button I think it needs active vaccum pressure.

 

[whitenemesis]

Not the most sensible of systems!
Surely a purely mechanical fallback should be available?

 

[Doodle]

Those are just the key positions of the boot opener. With my battery disconnected they had no impact on boot push button no matter what sequence I moved the key. Those positions only work if the battery is connected and has electrical power for activating the vacuum central locking. For the boot opener to function as a mechanical push button I think it needs active vaccum pressure.

The vacuum only works on the central locking solenoid, which moves the locking mechanism on the back of the barrel. The key will directly override that via the lock barrel, and there is a mechnical rod between boot lock mechanism and key barrel/button for opening.

The fact that the system worked normally once unlocked by the vacuum solenoid suggests the key you are using in the barrel is, or has been cut from, the valet key. This only works in door locks and ignition, not the boot.

 

[Fintail66]

The vacuum only works on the central locking solenoid, which moves the locking mechanism on the back of the barrel. The key will directly override that via the lock barrel, and there is a mechnical rod between boot lock mechanism and key barrel/button for opening.

The fact that the system worked normally once unlocked by the vacuum solenoid suggests the key you are using in the barrel is, or has been cut from, the valet key. This only works in door locks and ignition, not the boot.

These are the original twin master keys that came with the car. I think the post 1994 cars have no mechanical override over the vacuum central locking. I would assume the mechanical override exists in the C- class and E-class and even the SLK, but NOT in this SL!!

 

[Doodle]

double post

 

[Doodle]

I think the post 1994 cars...

Mine is registered early 1995.

 

[Y15HAL]

Mine is a 96 and can be opened with the key.