Interference loud static car won’t start

[Jaysubi53]

Good afternoon so I bought a Mercedes C63 w204 about a week ago I went out to the shops in it today and I heard a static noise from my speakers it got louder and then was making weird and random noises (a bit like when you put your phone near a speaker and call someone).

I decided whilst I’m stood still traffic to turn the engine off but it wouldn’t let me fully switch off and pull out the key and then it wouldn’t let me restart.
I put my hazards on put it in neutral and rolled it off of the road.
Some how o managed to get the key out then restart the car I quickly turned around and drove 15 minutes home. On the way home same issue noise from the speakers and even when I turn the car totally off and remove the key it continues.

Gutted as I’ve only had the car a week and everything seemed to be going well :-(

I’ve put a diagnostic reading device in and there’s no codes flagging up at all.

Sat in my car now stood still and the speakers make some random static kinda noise I very 10 minutes or so.

Anyone has this fault before?

I’m thinking maybe a wiring issue loose connection or something.

 

[John N]

Good afternoon so I bought a Mercedes C63 w204 about a week ago I went out to the shops in it today and I heard a static noise from my speakers it got louder and then was making weird and random noises (a bit like when you put your phone near a speaker and call someone).

I decided whilst I’m stood still traffic to turn the engine off but it wouldn’t let me fully switch off and pull out the key and then it wouldn’t let me restart.
I put my hazards on put it in neutral and rolled it off of the road.
Some how o managed to get the key out then restart the car I quickly turned around and drove 15 minutes home. On the way home same issue noise from the speakers and even when I turn the car totally off and remove the key it continues.

Gutted as I’ve only had the car a week and everything seemed to be going well :-(

I’ve put a diagnostic reading device in and there’s no codes flagging up at all.

Sat in my car now stood still and the speakers make some random static kinda noise I very 10 minutes or so.

Anyone has this fault before?

I’m thinking maybe a wiring issue loose connection or something.

I apologise that I can't help with your problem, but the details are very like the opening scenes intro to a UFO Film!

 

[Stratman]

Check the engine block to chassis connections. I don't know where they are on a C63, but they're undoubtedly subjected to constant flexing and perhaps spray. On other MBs they have been known to fray and the connection itself can become high resistance at either or both ends.

 

[Jaysubi53]

Check the engine block to chassis connections. I don't know where they are on a C63, but they're undoubtedly subjected to constant flexing and perhaps spray. On other MBs they have been known to fray and the connection itself can become high resistance at either or both ends.

Thanks for the reply.

Not a clue where to start on checking block and chassis connections but at a guess if say they were under the car?

I disconnected the battery for 5 minutes took the audio and radio fuses out then went on a 60 mile trip with no dramas on the way back I reconnected the fuses half hoping the problem would reappear but nothing! Cars working as it should like it should.

I do think it could be a loose connection or something but no idea where or how to investigate this further.

Thanks

 

[Stratman]

A mahoosive V8 may be different to my little four-pot diesel, but mine is in the general vicinity of the bellhousing/rear of the engine. They electrically connect the chassis (hence battery negative) to the engine and ancillaries and have a surprisingly hard life. They're constantly being flexed by engine movement and once a connection develops a tiny bit of excess resistance, the starter motor current which flows through it can cause localised heating leading to corrosion, oxidisation and poor contact, which will exacerbate the problem.

Of course it may have nothing to do with this but once you discover where it is it's an easy check.

 

[StMarks]

Perhaps get the alternator checked out.? ( Iirc Halfords / Kwick fit type places will often do so FOC on the grounds that they can discover a faulty unit and sell you a replacement)

 

[Jaysubi53]

Ok so I put both fuse’s back in turned the engine off then back on and the problem came back even just opening the a door with the key out of the ignition causes a static noise from the speakers. I take out fuse 26 in the engine compartment and it stops so at least I can drive without the interference just no stereo.

Thanks for the advice I may have to pop to Halfords or Kwik fit see if they can help.

Thanks

 

[clk320x]

I decided whilst I’m stood still traffic to turn the engine off but it wouldn’t let me fully switch off and pull out the key and then it wouldn’t let me restart.

You most likely didn’t put it into park; easy to forget when trying a quick restart in traffic.

 

[Jaysubi53]

You most likely didn’t put it into park; easy to forget when trying a quick restart in traffic.

Your right, I didn’t! I left it in drive tried to turn the key and nothing happened tried to take the key out but it wouldn’t let me so put it into Neutral rolled it to the kirb and then park and it worked I was definitely flapping at the time thinking the worst that makes me feel a bit better.

Thanks for your reply

 

[StMarks]

Ok so I put both fuse’s back in turned the engine off then back on and the problem came back even just opening the a door with the key out of the ignition causes a static noise from the speakers. I take out fuse 26 in the engine compartment and it stops so at least I can drive without the interference just no stereo.

So, you've located the source then Jaysubi53. Congrat's.!
What does the 20 amp fuse number 26 control on your C63 ?

 

[Diesel Benz]

Seems to be the head unit fuse. Odd that a misbehaving head unit can cause all that trouble. Perhaps confusing the CAN or could the car have some after market stuff connected to the same fuse.

 

[Petrol Pete]

Could this be the 'classic' duff alarm sender fault ?

I know I say this a lot on here

Distraught MBUK forum member ..." I have a conrod sticking out of the side of the engine block ! what should I do ?? Please help.

Petrol Pete ... "Have you tried unplugging the alarm sender..? "

But it a known electrical weak point and is sooo easy to eliminate from any electrical fault finding . Always worth doing before spending the big bucks in my opinion.

 

[Jaysubi53]

So, you've located the source then Jaysubi53. Congrat's.!
What does the 20 amp fuse number 26 control on your C63 ?

It’s for the command radio system so just to clear things up a bit there were no issues with starting the car basically I turned the engine off with the Drive still selected then tried to turn back on with it still selected this is why it didn’t start.

I’ve had fuse 26 out now and there’s no problems at all other than I can’t listen to any Audi.

What do you think I should do next? Id like to take it to a garage but have a feeling it won’t be cheap but also at the same time I’ve no clue where to start myself.

I’m going to try and re insert the fuse with the engine already running and see if it changes anything

 

[Jaysubi53]

Could this be the 'classic' duff alarm sender fault ?

I know I say this a lot on here

Distraught MBUK forum member ..." I have a conrod sticking out of the side of the engine block ! what should I do ?? Please help.

Petrol Pete ... "Have you tried unplugging the alarm sender..? "

But it a known electrical weak point and is sooo easy to eliminate from any electrical fault finding . Always worth doing before spending the big bucks in my opinion.

So with fuse 26 in and the engine off no lights on the dash etc I open the door the dash lights up then then the speakers make like a static pop noise quick pop then 10 seconds later another pop. That’s with no key in just opening the door for the dash to light up.

I’ll have a look at the alarm sender is it a fuse by any chance?

Thanks for your reply.

 

[Jaysubi53]

Managed to get a video just now.

So I started the car up with no fuse 26 in drive 10 minutes stopped kept the car running then re inserted fuse 26 and began to play some music straight away I noticed that the rear speakers in the parcel shelf sounded a bit tiny not enough to switch music off it was still listenable but I could here static.

Another 10 minute drive I pull up turn the music low and then switch the engine off take the key out dash light goes out after 15 seconds or so I hear static.

So this is the video now I open the door and close the door no key in and the dash lights up then you hear static at the beginning which is like a quick pop then you here the interference after about 15 seconds towards the end of the video.

I just wrote all that but can’t attach a video from my phone I’ll post this and attempt on my laptop

 

[Montreal300]

Has any aftermarket equipment been added to the car?

 

[Jaysubi53]

Managed to get a video just now.

So I started the car up with no fuse 26 in drive 10 minutes stopped kept the car running then re inserted fuse 26 and began to play some music straight away I noticed that the rear speakers in the parcel shelf sounded a bit tiny not enough to switch music off it was still listenable but I could here static.

Another 10 minute drive I pull up turn the music low and then switch the engine off take the key out dash light goes out after 15 seconds or so I hear static.

So this is the video now I open the door and close the door no key in and the dash lights up then you hear static at the beginning which is like a quick pop then you here the interference after about 15 seconds towards the end of the video.

I just wrote all that but can’t attach a video from my phone I’ll post this and attempt on my laptop

Has any aftermarket equipment been added to the car?

No nothing everything is standard

 

[Petrol Pete]

So with fuse 26 in and the engine off no lights on the dash etc I open the door the dash lights up then then the speakers make like a static pop noise quick pop then 10 seconds later another pop. That’s with no key in just opening the door for the dash to light up.

I’ll have a look at the alarm sender is it a fuse by any chance?

Thanks for your reply.

No fuse .

Even if you take the batteries out of the car the alarm sender will still make it's noise , it contains it's batteries inside it . That is the problem when they go wrong , they feed this voltage back into the car causing all sorts of weird and (not so) wonderful faults.

It's unlikely to be this at fault (I hope it is as it's an easy fix) and it's so easy to eliminate from the fault finding process unplugging it is a 'no brainer' in my opinion.

 

[Jaysubi53]

No fuse .

Even if you take the batteries out of the car the alarm sender will still make it's noise , it contains it's batteries inside it . That is the problem when they go wrong , they feed this voltage back into the car causing all sorts of weird and (not so) wonderful faults.

It's unlikely to be this at fault (I hope it is as it's an easy fix) and it's so easy to eliminate from the fault finding process unplugging it is a 'no brainer' in my opinion.

So where do I find this Alarm sender?

 

[Petrol Pete]

On RHD drive cars it's usually behind the front wheel arch liner passenger side. It can be accessed without taking the wheel off , but easier if the wheel is off.

Mercedes C Class (W203) Alarm Problems - Mercedes Gen-In

If your Mercedes C Class alarm starts to behave strangely with random false alarms sounding, indicators flashing without any alarm sound or even chirping whilst you are driving, then the number one cause for these issues is the siren module.

www.mercedes.gen.in