Have I bricked my CLS500? (W219)
Discussion
My MOT is due in the middle of Feb, so I booked it in nice and early (today) to work out any potential issues.
The only potential failure I can see is a number plate bulb, which I was going to replace. Go to unlock it at the weekend and it's dead to the world. Odd as it was driven over 100 miles with no issue a week ago. I have a look at the battery to see if anything has come loose or anything silly and it's rock solid.
To save any future faff I pop down to Euros and pick up a new battery and after fighting with the old one for a bit (really wasn't expecting that extra bracket) I install the new one.
Car fires right up, but I see I haven't done a great job on that positive terminal so I go ahead and give it a little tighten up with my socket wrench. There's a small spark, and the car dies. I tighten it up properly and fire the car back up. This time it's not happy the positive terminal starts smoking (I now know it was actually expelling toxic gases) the car runs a bit odd, and there's a battery protection warning on the dash so I turn it off and disconnect the terminals quickly.
I let it cool down and connect it up properly this time. New battery is dead. I assume I've knackered it. I remember I bought a battery re-conditioner a few years ago that's in a cupboard I bring the old battery into the house charge it overnight.
Old battery goes back in this morning after getting a full charge - car fires right up no complaints. Let it idle for a while I stare at the terminals to make sure it's all fine and all checks out. Go out for a little drive and that warning about battery protection comes back. I park it up and have a look at the battery and I can't see anything visually wrong.
I call out my breakdown cover and an hour later the car fires up fine but still with that warning light. The positive terminal then melts his multimeter for good measure so we shut it off disconnect the negative and his recommendation is to scrap it as I've likely short-circuited one of many ECUs and reveresed the polarity of the battery.
It's a shame though it's a great car runs perfectly has zero corrosion and it's a lovely combination of low tax and V8.
I can't get an autoelectrician to look at it until Thursday and the call-out charge is £90, so I'd like to ask for all of your collective help to save a lovely old car from the scrapheap.
What do you all reckon have I ruined it? Could there be an easy fuse or relay somewhere? The intention was always to sell it around March/April time so I don't want to get into a large investigation when it's not a long term prospect but it deserved to live on and find a happy home.
The only potential failure I can see is a number plate bulb, which I was going to replace. Go to unlock it at the weekend and it's dead to the world. Odd as it was driven over 100 miles with no issue a week ago. I have a look at the battery to see if anything has come loose or anything silly and it's rock solid.
To save any future faff I pop down to Euros and pick up a new battery and after fighting with the old one for a bit (really wasn't expecting that extra bracket) I install the new one.
Car fires right up, but I see I haven't done a great job on that positive terminal so I go ahead and give it a little tighten up with my socket wrench. There's a small spark, and the car dies. I tighten it up properly and fire the car back up. This time it's not happy the positive terminal starts smoking (I now know it was actually expelling toxic gases) the car runs a bit odd, and there's a battery protection warning on the dash so I turn it off and disconnect the terminals quickly.
I let it cool down and connect it up properly this time. New battery is dead. I assume I've knackered it. I remember I bought a battery re-conditioner a few years ago that's in a cupboard I bring the old battery into the house charge it overnight.
Old battery goes back in this morning after getting a full charge - car fires right up no complaints. Let it idle for a while I stare at the terminals to make sure it's all fine and all checks out. Go out for a little drive and that warning about battery protection comes back. I park it up and have a look at the battery and I can't see anything visually wrong.
I call out my breakdown cover and an hour later the car fires up fine but still with that warning light. The positive terminal then melts his multimeter for good measure so we shut it off disconnect the negative and his recommendation is to scrap it as I've likely short-circuited one of many ECUs and reveresed the polarity of the battery.
It's a shame though it's a great car runs perfectly has zero corrosion and it's a lovely combination of low tax and V8.
I can't get an autoelectrician to look at it until Thursday and the call-out charge is £90, so I'd like to ask for all of your collective help to save a lovely old car from the scrapheap.
What do you all reckon have I ruined it? Could there be an easy fuse or relay somewhere? The intention was always to sell it around March/April time so I don't want to get into a large investigation when it's not a long term prospect but it deserved to live on and find a happy home.
I think its certainly worth a second opinion from a pro.
The battery protection warning normally refers to low battery charge so it shuts non-essential functions down (if thats the warning it is) and I don't understand the connection between the recovery man frying his multimeter on the positive terminal and the fault as he describes.
I'd be amazed if the car worked at all if you'd kippered the ECU.
The battery protection warning normally refers to low battery charge so it shuts non-essential functions down (if thats the warning it is) and I don't understand the connection between the recovery man frying his multimeter on the positive terminal and the fault as he describes.
I'd be amazed if the car worked at all if you'd kippered the ECU.
I suspect it’ll be a reasonable repair too. Some cars do shut down non-essential electrical systems if they detect a low battery. On an older car I would suspect a fuse first of all. It does sound like the new battery was faulty. I wonder whether the plates were shorting. Either way, an ECU normally works or it doesn’t. They are often protected circuits too. There are scare stories about jump starts damaging ECUs but this sounds like a straightforward battery swap.
Raiden61 said:
Thanks Robert!
It works perfectly fine as a car, gearbox, engine steering, even the air suspension works like normal I'm just not allowed to use the heated rear window or heated seats or cigarette lighter.
Er have you replaced the starter battery (under the bonnet) or the consumer battery in the boot?It works perfectly fine as a car, gearbox, engine steering, even the air suspension works like normal I'm just not allowed to use the heated rear window or heated seats or cigarette lighter.
(I’m assuming that your car is like the SL whereby it has two batteries; the consumer battery is the one that runs your heated seats, hrw, stuff like that.)
If your car does run this system then it sounds like it’s your BMS that’s knackered. On an SL it lives somewhere in the boot and on earlier cars that have a habit of setting on fire. There are companies that rebuild them or make new ones.
I can’t give you any more info as I only know SLs but it does sound like a BMS. Check both batteries.
Mr E said:
I was going to say the same thing. There is very likely more than one battery in the car.
Yep I’ve checked and it’s the same as the SL. I’d first be checking that the consumer battery is ok and then looking at the BMS; there are plenty of people online various Merc forums who’ve had BMS failures and companies who make replacements.
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