It amazes me that designers don't anticipate this sort of thing. A flat battery is hardly unusual so you would like to think they've made provision for this scenario. Most of my recent modern cars have had remote jump lead terminals in the engine bay, your SL may have something you've not spotted?
Alas I cannot open the bonnet either. Internal release, and the doors are locked too. The soft-top is up, so there is a little scope for using a wire to open a door pull.
The lockup doesn't have electricity, so the scope for trickle charging is low
I'm thinking a spare battery, connected to an inverter, connected to a trickle charger - but that operation will have to wait.
Is there not a concealed keyhole in the handle? It's like MB almost wanted to punish owners for allowing the battery to go flat 😳
Post by grumpynorthener on Dec 1, 2023 22:14:16 GMT
Talking to my local garage owner Mark yesterday who does my testing along with anything on the moderns for me - He has a R129 SL300 along with a nice XJ 40 - apparently the one thing that you must not do with R129 is jump start it as this cooks the roof module leading to further tales of woe - You should be ok to connect a power source in order to operate the locking and get into the boot but then remove / recharge / replace the battery - don't attempt to jump start the car from another external source for the above reasons
I found some time over the holidays to take a look at the Mercedes.
Just about enough room in the lock-up to get a trolley jack in and get it up in the air.
With it in the air, I could clearly see the alternator. So, I was able to connect the battery charger. But the lockup has no power, so I bought this useful little box which provides mains power from a built in battery.
After about 10 mins, I was able to operate the central locking and undo the boot where the battery lives. I removed the battery and took it home for a proper charge. Hmmm not good.......
But I took it back to the lockup and started up the car to see what the damage might be. Window control ECU - probably screwed as the drivers window went down, and now won't come back up. Hood control ECU - probably screwed as the catches in the header rail don't attempt to release. I've released them manually, so I know they aren't siezed.
So it looks like I'll be following in toomanyprojects footsteps to get the electrics sorted. But it will wait until the spring, no enthusiasm for it any more.
It is faintly ridiculous that a car can grenade itself so thoroughly with something as simple as a flat battery. Mercedes SL500 - consider your copybook blotted
Post by toomanyprojects on Jan 2, 2024 11:55:38 GMT
I feel your pain... suffice to say, been there done that.
The windows and roof ECU are all one unit, so you may find that with a fresh battery that rectifies itself through the reset procedure - does the hood button show as permanently red?
The hardtop light isn't permanently on, so maybe there is hope.
I guess I'm wasting my time doing any further diagnostics until fitting a fresh battery.
What worries me, with the engine running, the passenger side window goes up and down, but the drivers doesn't - it went down, but now won't come back up.
The hardtop light isn't permanently on, so maybe there is hope.
I guess I'm wasting my time doing any further diagnostics until fitting a fresh battery.
What worries me, with the engine running, the passenger side window goes up and down, but the drivers doesn't - it went down, but now won't come back up.
Ok so that's good news, if it was red then that's a whole new can of worms.
Yup, fresh battery and then try resetting things - just press and hold the window switches (both) and go all the way down and hold for 10 secs, then all the way up and hold for 10 secs, may be worth doing a couple of times. It may also be worth checking the earth straps, as that also contributed to some of the issues I experienced.
Alas in the cold light of day, only now I'm noticing the spelling mistakes in the advert, hopefully I've found most of them now.
But more importantly, had a wonderful 40 mile drive around the Hampshire lanes last night. Very enjoyable. ...and my god it is fast when it wants to be
