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My manual trunk lock with the key does not work (95 420S) and my battery has died over an extended period of not being used.
I tried supplying power through the cigarette lighter with a 12V battery pack but it did not work for the trunk release button (the SRS light came on but no other electronics activated).
Where under the hood would be safe to apply a booster/charger? Figured the alternator but not even sure where it is on that vehicle.
Can you get to the trunk via the back seat?
I just need to access the trunk so I can swap out or charge the battery.
My manual trunk lock with the key does not work (95 420S) and my battery has died over an extended period of not being used.
I tried supplying power through the cigarette lighter with a 12V battery pack but it did not work for the trunk release button (the SRS light came on but no other electronics activated).
Where under the hood would be safe to apply a booster/charger? Figured the alternator but not even sure where it is on that vehicle.
Can you get to the trunk via the back seat?
I just need to access the trunk so I can swap out or charge the battery.
Any ideas appreciated.
Viking87
you are asking yourself exactly the right questions!
The trunk battery is supplied by a thick gauge red cable.
Does your chassis feature JUMPER POSTS ?
Show us a picture of your engine bay particularly on both sides.
Empty flat battery acts as a heavy SHORT-CIRCUIT. It may not charge at all.
Don't jump start your car engine now to fry your Alternator. Need charged up battery first.
Knew not to start it because when I acquired the vehicle the speedometer had failed from boosting. I was able to diagnose and repair the guilty red 10 amp fuse thanks to this site. I have two batteries (one I saved form my 560SEC) so will swap it once I gain trunk access.
Will take some pictures in the morning light and add to this thread. Have never notice jumper posts in the engine bay but haven't really looked for them either. Engine has a huge plastic cover that needs to be removed before you can see anything.
Try hooking a battery booster in the passenger floor area. There should be some red wires under a panel under the floor mat. Ground to anything metal like the seat rails. Connecting the battery booster is only to try to get power to get the trunk opened. Dont try and start the car or even put the key in the ignition.
I dont have the S420 so just getting my info from searching around.
I believe i have the correct Operators manual. It says the trunk can be manually opened with the key. For jump starting it says jump right off the battery. So it should be possible to open the trunk with a dead battery.
For the passenger compartment it houses the X4/10 terminal block 30/30U. When i look at the wiring diagrams this looks like a good place to jump in to since it leads to the + battery. From the photo above it looks like theres some tabs at the top of the panel, try pulling them towards you. Or look for a few bolts/screws.
Tim
Wow! Thanks for the detailed instructions. Have saved and will print them for reference.
Cali
Thanks for confirming. I will try to enlist the help of my neighbor to actually undertake any of this. Have to remove some snow so can get proper access through passenger door. It did look like tabs at the top of that metal plate.
Was raining out today so will wait for better weather. Might solve the snow problem without my intervention. Will report back if successful or require further assistance.
The manual lock on the truck has something jammed in it (the key won't go all the way in). Might try to resolve that is order to gain access first.
I just want to power up the system enough to pop the trunk with the button on the dash. I have a good battery that is currently being used in another vehicle that I will install before I try to start it.
I dont have the S420 so just getting my info from searching around.
I believe i have the correct Operators manual. It says the trunk can be manually opened with the key. For jump starting it says jump right off the battery. So it should be possible to open the trunk with a dead battery.
For the passenger compartment it houses the X4/10 terminal block 30/30U. When i look at the wiring diagrams this looks like a good place to jump in to since it leads to the + battery. From the photo above it looks like theres some tabs at the top of the panel, try pulling them towards you. Or look for a few bolts/screws.
I could be totally wrong.
Sorry for the delay. Weather has been poor and first nice day to take a closer look.
Metal plate removed with two nuts at the base (10 mm of course).
The big red arrow (last picture) seems to have a battery cable connected to it. There (with the red positive) and seat rail (with black)? Any where closer than seat rail for ground?
My neighbor is away so will try this on my own if someone can verify.
I think that large wire goes back to the battery. To double check take your multimeter set to continuity and test it to the two locations with the green arrows. If it beeps then connect your positive to the large nut/wire.
I just cant see if there is a bushing or something under that large wire nut separating it from the red wires. They look all connected on the metal bar underneath.
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