w220 350 electrical problem

[bonchester]

No problem with using jump leads if you do it right.
made the same mistake on my w124 moons ago and it was the OVP, but the problems were everywhere.
The W220 was however the start to electronic everything in mercs.

doesnt help the op but is as

What we're the problems? I just don't know how to go about this. Is there a fuse behind the trim where the battery is? Is there a fuse underneath the carpet in passenger footwell? What does anyone suggest what I should do to try to resolve this? Any suggestions would be welcomed.

 

[mattkh]

Is this a true sequence of events :-
Your wife is in the car, the drivers door is open, the bonnet is open, the interior light is on and very dim, the ignition key is in your pocket, you connect the black jump lead to the +ve terminal of the battery, then you connect the red jump lead to the -ve terminal, then you sit in the car and put the key in the ignition.
What happened next..?

 

[mioba]

To be fair OP. I would take the car to a merc indy or even your dealership and pay for the lesson learned and explain them the series of events what happened. I ask about an OVP as this may well have popped causing your woes.

 

[bonchester]

Bonnet open,boot open,drivers door open,no-one in the car,key in ignition. Attached jump leads correctly to the car,then to attach leads to the other car stupidly connected positive to negative terminal on donor car. Almost immediately realised my mistake,it was very dark,wet blowing like hell,disconnected said lead and connected them correctly. Car wouldn't start. Checking all the fuse found 2 40 amp ones ,under the rear seat,blown. I replaced them and the car started. Then I realised that certain functions were not working. Took it to my indy who diagnosed right sam. Got the correct part number from mercedes and bought one. I photographed the position of all fuses relays,connections etc and replaced the old sam. It did not alter anything. Checked all fuses,relays with a multimeter ,all was well. As I said before I am OK with spanners but this stuff is beyond me. I thought the sam was plug and play but I have been told by a gentleman in a previous answer that it should be coded. So what doesn't work -- seat adjustment/heating, folding mirrors,drivers windows,horn ,command, ac,drivers side light indicators, airmatic. That's about it. Are there any other fuses under carpets? Has this model got an ovp? Any thoughts would be extremely welcome . Thanks.

 

[mattkh]

Thanks.
On the windscreen what are the 6 numbers after WDB------?

 

[peterws1957]

Bonnet open,boot open,drivers door open,no-one in the car,key in ignition. Attached jump leads correctly to the car,then to attach leads to the other car stupidly connected positive to negative terminal on donor car. Almost immediately realised my mistake,it was very dark,wet blowing like hell,disconnected said lead and connected them correctly. Car wouldn't start. Checking all the fuse found 2 40 amp ones ,under the rear seat,blown. I replaced them and the car started. Then I realised that certain functions were not working. Took it to my indy who diagnosed right sam. Got the correct part number from mercedes and bought one. I photographed the position of all fuses relays,connections etc and replaced the old sam. It did not alter anything. Checked all fuses,relays with a multimeter ,all was well. As I said before I am OK with spanners but this stuff is beyond me. I thought the sam was plug and play but I have been told by a gentleman in a previous answer that it should be coded. So what doesn't work -- seat adjustment/heating, folding mirrors,drivers windows,horn ,command, ac,drivers side light indicators, airmatic. That's about it. Are there any other fuses under carpets? Has this model got an ovp? Any thoughts would be extremely welcome . Thanks.

First thing I would do is look on the website Fuse Box Info to check whether you have covered all the fuses and see if there is anything which links all the failed components you describe. The sam you replaced does not encompass all those components. If no clue there, I'd be contacting a few auto electricians and explaining what you did, what you have replaced, and what are the symptoms you still have and see what kind of response you get. You never know it could be one relay that needs replacing.

Alternatively get back to your indie and have another STAR diagnostic. Only as a very last resort and at the end of my tether would I be taking this to an MB dealer - an eye watering bill would ensue and possibly a "sorry sir we could not trace the fault" to go with it. Hope you get it sorted - so much hassle for a moments inattention. I did it once on one of my elderly cars - not one single fuse or relay blew.

 

[bonchester]

Thanks.
On the windscreen what are the 6 numbers after WDB------?

2200672a368172

 

[bonchester]

Ideas of where to purchase a new sam if it becomes necessary?

 

[Botus]

I think this thread is unraveling... lets start at the beginning,

this model was the first electronically super complicated model Merc ever did. It has lots of computer modules linked up in a very early iteration of can bus electronics

experience tell us when it misbehaves, it does so in multiple unfathomable weird and wonderful ways that even great experts using dealer diagnostic kit find mindbogglingly frustrating

sometimes even after every ECU module has been swapped out and coded to each location multiple times you still can't get anything to make sense from one day to the next in the workshop

and then often after months fighting silly simple little fault codes that won't go away across multiple modules (resulting in various functions / features being a little random in operation), its been discovered even cars that are "like new" have had unknown puddles under the carpet making the can bus go mental

usually its connections under the carpets that look perfectly good but somehow causes low resistance due to the damp, these can cause just enough conductivity issues on the early can bus system it never sends the right signals round the car and it behaves like a computer virus on a network (where you are just chasing your tale and getting nowhere). Half the time its the can bus and corrosion, and the other the tech thinking about one quick idea comes back to the car to try an idea and forgets the power supply to keep the volts up. And we end up with many hours wasted with a module "offline" due to low voltage whilst testing a replacement

on this car likely all points above, plus a volt spike connecting back to front. So to save workshop time.

1) ensure the battery is tip top.
2) remove the carpets and dry out the whole interior even if you think its bone dry
3) remake every multiplug, wiring connection and earth point on the whole car (and liberally get ACF50 on anything electrical)
4) open up all the SAMs and look for signs they've blow their brains out and or had a bath
5) replace all fusible links and remove test and remake every fuse location around the whole car (and use ACF50 before refitting them)
6) then with a 14v power supply and dealer kit try and get the car to wake up and behave...
7) maybe have known good SAMs at hand to swap out and code to the unique set up of your car before trying point 6 again when it doesn't help
8) when happy check the alternator output meets spec (I guess this could come earlier - but this is not the driver of diagnostic fault codes or toys not functioning)

 

[bonchester]

Just fills me with dread! Think I will scrap it if after having someone else xentry the car. Its just not worth the cost.

 

[mattkh]

Just fills me with dread! Think I will scrap it if after having someone else xentry the car. Its just not worth the cost.

Pressing the reset button is employed widely in electronics.
How do you feel about disconnecting the negative terminal of the car battery, waiting half an hour, and then reconnecting, and test.

 

[bonchester]

That's not a problem as a new fault has raised its ugly head this afternoon - the car is not charging the battery now! I don't even think I could drive it to the dealership due to suspension is now very low and as the dealer is about 30 miles away the battery wouldn't last.

 

[Paul Garrett]

That's not a problem as a new fault has raised its ugly head this afternoon - the car is not charging the battery now! I don't even think I could drive it to the dealership due to suspension is now very low and as the dealer is about 30 miles away the battery wouldn't last.

OMG! i wish i could help you as this is driving you nuts!! When it comes to car electrics i stay well away as im a complete dunce on those matters

 

[bonchester]

Yes it is. I am the same - useless! Almost ready to scrap it

 

[mattkh]

Almost ready to scrap it

Don't scrap it, its not a diesel engine.
I reckon the charging light is a blessing in disguise. Charging could very well be the original problem, which is why you had to use the jump leads.
Disconnect the battery and put it on charge for 24 hrs.
Also check the wires at the back of the alternator.

 

[bonchester]

I have an auto electrician coming to have a look at the "thing" let's see before I strike the match! I can't drive it now because the suspension has lowered and of course the charging problem.

 

[mioba]

was your car last serviced at MB, if so you will have mobilo

 

[bonchester]

I do about 2k miles a year in it and do my own servicing ,oil filters,brakes etc all else is done at my local garage so no mb service in the 3 years I have had it.

 

[Botus]

connecting any car back to front has always blown the brains out of the rectifier pack (diodes in the alternator), on most Mercs these are a replaceable item for not much money

the fact is started was a miracle after what you did, if body wise and mechanically its like new (especially if you replaced all 4 suspension struts - as these don't last 10 years on the w220), then worth the fight. but if a bid of a dog >70k miles its done u a big favour

 

[bonchester]

connecting any car back to front has always blown the brains out of the rectifier pack (diodes in the alternator), on most Mercs these are a replaceable item for not much money

the fact is started was a miracle after what you did, if body wise and mechanically its like new (especially if you replaced all 4 suspension struts - as these don't last 10 years on the w220), then worth the fight. but if a bid of a dog >70k miles its done u a big favour

It's a very sound car with 125k miles. Will look at the alternator and thanks for your input.