Has jump starting my car fried the electrics?

Mikemccann

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Hi all

I have a 2000 CLK 320 Auto Convertible that suddenly wouldn't start last week. I decided it might be a flat battery so I tried jump starting it from my wifes car.

I DEFINITELY connected the jump leads red to red and black to black but after about 30 seconds the heavy duty jump leads simply melted with extreme heat near the battery in my Merc! I assume a short in the electrics somewhere in the car or a faulty battery

I want to try to connect another battery but cannot open the boot. I have tried using the switch in the center console and the master key in the boot lock (it wont go more than half way in) . I have also tried connecting another battery using the terminal near the fuses under the bonnet - but to no avail. Everything is dead!!!

So...... I cannot start the car, the battery is dead and I cannot open the boot :(

2 questions

1) Is it likely I have fried all/some of the electrics in the car ?
2) Can I open the boot without using a key?

Many thanks for your help.

Mike
 

Wighty

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Not sure if it would make a difference , but if you read your cars manual for jump starting it wil be red to red and black to cars earth point . Oh and welcome to the forum
 

turbopete

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Not sure if it would make a difference , but if you read your cars manual for jump starting it wil be red to red and black to cars earth point . Oh and welcome to the forum
makes no difference at all.
 

ernieh

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Easy things first....the lock in the boot is probably seized through lack of use, so liberally spray the key and the lock with a penetrating oil and work the key in and out until it frees off enough to turn in the lock. Hopefully, that should get the boot open.

As regards the electrics, they really need to be checked out with a multimeter, but I think there may be a large fuse in the battery circuit which has blown. Somebody else may be able to help you locate that fuse, but, clearly to melt your jump cable and possibly blow the fuse, there must have been a heavy current draw from somewhere, maybe the starter motor. Before trying to start it again, I would be checking the starter.

Let us know how it goes.

Ernie
 

Dell

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The fuse should be under a little black cover near the battery about 2” by 1” but if that had blown then it would not have melted jump leads,
Did you try to start it ? Did the starter turn ? If so and the jump leads never made a solid contact then turning starter would overheat jump leads
 
OP
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Mikemccann

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  • Thread Starter
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Thanks for your replies.

Yes, I did try and start the car whilst the jump leads were connected but the engine did not turn at all. I cannot get to the fuse near the battery as I cannot open the boot. Will try lubrication to see if that lets the key work - if not, is there any other way of opening the boot?
 

Dell

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Not sure about your car but some cars if you remove back seat then you may be able to get into boot from there .
Sorry but that’s the only suggestion I have.
 

Submariner1

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makes no difference at all.

Not what I was told by both the Main Dealer technician and Mobilo guy on a C216! For a tiny CTEK 3.6A trickle charger and jump starting ( but both said dont jump start and specifically do not use one of those booster power packs).
Because of the battery control module. :-/

But maybe his car is different :-/
 

LostKiwi

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Not what I was told by both the Main Dealer technician and Mobilo guy on a C216! For a tiny CTEK 3.6A trickle charger and jump starting ( but both said dont jump start and specifically do not use one of those booster power packs).
Because of the battery control module. :-/

But maybe his car is different :-/
CLKs have a much simpler system with no battery control module and only a single battery so as stated it makes no difference.

OP, you must have had either tiny jump leads or a huge current draw to melt your leads.
What size leads were you using?
 

Steve@Avantgarde

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There is nothing wrong with using a booster pack, as long as its a 12v one. If the car is flat, connecting a 12v 100ah booster pack is like fitting a brand new battery. So you go through the same procedure you would for that. EG: headlights on, connect jump pack, leave to stabilise for 2 mins, crank engine.

Jump leads are a whole different scenario because you are connecting from a charging battery, unregulated at around 16.5v and a spiked wave form. That is dangerous and will fry electrics.

Specifically we don't know if the op has a flat battery. Is there any mileage display on the instrument cluster? Interior lights working? If so, could it be an EIS issue or key fault? More info is key here.

Good news here is that the car is an old W208, they are fairly robust creatures. Other things that cause non starts on these are earth straps on the gearbox to body corroded.
 

EmilysDad

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Not what I was told by both the Main Dealer technician and Mobilo guy on a C216! For a tiny CTEK 3.6A trickle charger and jump starting ( but both said dont jump start and specifically do not use one of those booster power packs).
Because of the battery control module. :-/

But maybe his car is different :-/

I
There is nothing wrong with using a booster pack, as long as its a 12v one. If the car is flat, connecting a 12v 100ah booster pack is like fitting a brand new battery. So you go through the same procedure you would for that. EG: headlights on, connect jump pack, leave to stabilise for 2 mins, crank engine.

Jump leads are a whole different scenario because you are connecting from a charging battery, unregulated at around 16.5v and a spiked wave form. That is dangerous and will fry electrics.

Specifically we don't know if the op has a flat battery. Is there any mileage display on the instrument cluster? Interior lights working? If so, could it be an EIS issue or key fault? More info is key here.

Good news here is that the car is an old W208, they are fairly robust creatures. Other things that cause non starts on these are earth straps on the gearbox to body corroded.

When ever I've used jump leads, the donor car has always been switched off when connecting the leads. Start donor car, leave running a minute then try starting the dead car.
 

LostKiwi

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I


When ever I've used jump leads, the donor car has always been switched off when connecting the leads. Start donor car, leave running a minute then try starting the dead car.
I think we had instructors from the same college.....;)
 

John Laidlaw

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Green flag once fried the ECU in my Volvo V70 when they connected the leads the wrong way around from a booster pack...professionals eh?
 

splitshift

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Hi all , I have a clk convertible, same age. The wire, big red one from the battery to the starter was shorting out on the floor, as it went through. Not always and very difficult to detect. It did however attempt to melt jump leads one day !!! Check that !! As to opening the boot, I am assuming we have no power , as we needed a jump in the first place ? Battery and jump leads via the underbonnet power points and I managed to fire the centre consul mounted button. Getting in via the rear seat is possible, but not sure if it would help, mechanism all covered in plastic !! I eventually had to drill out my lock to get in when I had flattened my battery, not pretty, and expensive !! Release oil and lots of key jiggling!!! Jaguars of old, xj8 etc, I used to always check behind the rear number plate, they were prone to boot release handles seizing, off with plate, drill hole and access rods. MIGHT be worth having a look........?
Hope you get it, Scott
Ps, leave a door open when jiggling keys etc, if battery is low, no telling when the central locking might drop! I know it’s vacuum but metal things in the wrong place can trigger circuits ! And, don’t break the key . Also !!! See if you can get any powdered graphite and rub the key in it this helps keep the mechanisms smooth and rust free, rubbing with a pencil does the same, obviously when you get the key working !!
 

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When ever I've used jump leads, the donor car has always been switched off when connecting the leads. Start donor car, leave running a minute then try starting the dead car.

And what about the 16v+ surge from the car on crank? The jump leads are unregulated pushing 16v straight out of the alternator. On a modern car with 30+ ECU's on them thats highly dangerous.

Cars do not have surge protection from spike wave form charging. Thats why all of my battery support units and boosters are flat wave form.
 

LostKiwi

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And what about the 16v+ surge from the car on crank? The jump leads are unregulated pushing 16v straight out of the alternator. On a modern car with 30+ ECU's on them thats highly dangerous.

Cars do not have surge protection from spike wave form charging. Thats why all of my battery support units and boosters are flat wave form.
If you connect battery to battery whats the difference? Effectively all you have is a large capacity battery at half charge.
 

turbopete

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If you connect battery to battery whats the difference? Effectively all you have is a large capacity battery at half charge.
that's the way I have always done it. both cars off, connect leads, start donor car, start (or try to) flat battery car. my experience has always been that the car with the 'good' battery will then start to charge the 'dead' battery as its little or no different in principle to a caravan battery being charged when on the go. it is also little or no different to replacing the battery on the 'dead' car with a brand new battery and starting the car. in both cases the voltage will be around 13v when connected (give or take a volt or so) and spike to between 15 and 16 volts when the car is started. also if voltage spikes are a major concern, there are (and have been for at least 20 years) jump leads with surge protection built in available, like these

https://www.ebay.co.uk/itm/Booster-...323507&hash=item568cfccadd:g:zy4AAOSwfxJZ6rGI

or these

https://www.craigmoreonline.co.uk/d...MI68T_39mO1wIVRDPTCh04QwmcEAQYASABEgIAUvD_BwE
 
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