Opening boot with a flat battery

[tromppost]

The battery on my S320 was flat at the weekend and I had to call the AA to jump start it, only because with the battery being flat I can not open the boot. Is there any way round this as I do not have a spare battery to get any power to the car to open the boot.
Also the car is not getting used much only done 55 miles since Sept last year. I should get a solar powered charger but this may not work throw the cigar lighter with out the keys in the ignition.

 

[wemorgan]

Is the S320 similar to the W208 CLK in this respect?

If it is, try this thread. It worked for me. You're looking for the small black box with 'X' on the top right of the engine bay photo.

HTH.....apologies if this is a red herring.

 

[verytalldave]

Cant you open it manually using the key blade stored in the fob?

 

[tromppost]

Is the S320 similar to the W208 CLK in this respect?

If it is, try this thread. It worked for me. You're looking for the small black box with 'X' on the top right of the engine bay photo.

HTH.....apologies if this is a red herring.

Thanks but not on this model. On the 2003 I think they have one.

 

[tromppost]

Cant you open it manually using the key blade stored in the fob?

No I tried this but the boot has some sort of closing mechanism that will not release with out power.

 

[DieselE]

Cant you open it manually using the key blade stored in the fob?

As a variation on Dave's suggestion, can you use the key blade to open the driver's door? Once inside the car you could release the bonnet and then find a point where the positive feed comes through from the boot to attach a jump start lead.

 

[tromppost]

As a variation on Dave's suggestion, can you use the key blade to open the driver's door? Once inside the car you could release the bonnet and then find a point where the positive feed comes through from the boot to attach a jump start lead.

Thats way beyond my skills, the AA man did it by using a bit of wire to the starter motor (i think it was that), he also had a small mobile charger.
Its a real pain that it does not a have jump starting point in the engine bay like most other cars. Its got an other 4 or 5 weeks of not getting used then after that I think its a new battery and a good wash.

 

[Dec]

I would be very surprised if you don’t have something like this somewhere, under bonett, under a cover of some kind, see picture…Its for a W202.

Dec

 

[tromppost]

I would be very surprised if you don’t have something like this somewhere, under bonett, under a cover of some kind, see picture…Its for a W202.

Dec

Thanks I will have a look for that at the weekend.

 

[alibally]

If you are going to leave the car for any time and there is a danger of the battery going flat the get a power point fitted under the bonnet to enable you to get the boot open. Are you sure there is not a keyhole beside the boot handle? I thought there was.

 

[tromppost]

If you are going to leave the car for any time and there is a danger of the battery going flat the get a power point fitted under the bonnet to enable you to get the boot open. Are you sure there is not a keyhole beside the boot handle? I thought there was.

Thanks the key releases the boot but it will not open, its held back be some sort of mechanism.
wemorgan and Dec have pointed me towards a possible jump point under the bonnet, I will have a look at the weekend.

 

[mr. shr]

Thanks the key releases the boot but it will not open, its held back be some sort of mechanism.

Are you sure? I thought the metal key worked regardless of whether the battery had power or not.
It's quite common for the lock mechanism to cease, but if your lock is fine then I would have thought you'd be able to open the boot with the metal key?

 

[Diesel Benz]

Are you sure? I thought the metal key worked regardless of whether the battery had power or not.
It's quite common for the lock mechanism to cease, but if your lock is fine then I would have thought you'd be able to open the boot with the metal key?

I was wondering the same. The owner must take care of the mechanical key working because it may not only be the flat battery making the electrical opening system useless. One often needs to access the wires at the trunk or the fuse to operate a broken electrical system, obviously not easy if the trunk cannot be opened.

I've never had this accessory where the boot has a pair of additional locks, I wonder it the car in question had these and would that be different. I have difficulties figuring out how the mechanical key could open these additional locks. Anyone already studied this?

 

[Wezzel]

Simple.

Unscrew a number plate light cover and put 12v across the terminals. This should give you enough power to use the central locking

 

[mr. shr]

I've never had this accessory where the boot has a pair of additional locks, I wonder it the car in question had these and would that be different. I have difficulties figuring out how the mechanical key could open these additional locks. Anyone already studied this?

Ah yes, I forgot about the factory option to have an additional lock on the boot. Is that what the OP has?

 

[mr. shr]

Simple.

Unscrew a number plate light cover and put 12v across the terminals. This should give you enough power to use the central locking

Will this not just blow a fuse? (Or something more sensitive?)

 

[Diesel Benz]

Will this not just blow a fuse? (Or something more sensitive?)

Hopefully the fuse and nothing from the rear SAM. There are plenty of simpler means to charge the battery, it does not help a lot if the licence plate bulb is close to the trunk lid lock.

If this was a serious proposal, I'd like to see it explained against the wiring diagram.

 

[nigel cross]

Cant see that working. If put wrong way round it will cause problems and if the correct way round might cause a problem but wont charge battery unless lights were left on as light switch would turn off power to lights, or disconnect battery from lighting circuit

 

[Wezzel]

The number plate light trick was told to me by a very good auto electrician who does a lot of work on Mercs with dead batteries.

I've not had to use it myself but I've no reason to doubt him.

Incidentally, it's not supposed to charge the battery - just get enough power into the car's electrics to enable the central locking to function.

 

[Diesel Benz]

The number plate light trick was told to me by a very good auto electrician who does a lot of work on Mercs with dead batteries.

I've not had to use it myself but I've no reason to doubt him.

Incidentally, it's not supposed to charge the battery - just get enough power into the car's electrics to enable the central locking to function.

I'd like to keep an open mind for suggestions like that but on a W220 the licence plate bulb is driven by the rear SAM and the PSE is connected to the rear SAM via CAN bus, how can you get enough power to the PSE from the bulb via the SAM (and not charging the battery enough to raise its voltage to a decent level?

I believe it is easier to put a cell phone next to the door lock and use the key next to another phone further away while calling to the phone next to the car.

Things could be different on older cars, but there again the light switch should be pretty mechanical and keeping the licence plate bulbs completely disconnected from the rest of the car when lights are off.