Having a nightmare - help please!

[bluejmc2005]

Evening all,

I have had a nightmare. I was at a wedding from 11.30 today, at 7.30 (literally as the first dance is beginning) I get frantic calls from my teenage daughters. The car - my 2010 CLS350 - is making a horrendous sound and they cant stop it. They say it started after a particularly strong rain/hail shower. Alarm I assume, but no its clear that its the horn. I talk my eldest through unlock/locking, putting ignition on, nothing stops it, neighbors out complaining- my wife and I have to live our dear friends wedding to get home. When I get home, sure enough the horn is continuously going, coming from front passenger side. Pissing down with rain so I cant make out where it is other than the general area. Nothing I do with the car stops it, aside from disconnecting the battery - which I do to stop neighbors lynching me. I check the fuse diagram, find the horn fuse and remove it (under the bonnet) reattach the battery - no horn. Marvelous, seems the rain has shorted the horn I think. But no, umpteenth error messages appear on the car, SBS,ABS and everything else. Maybe the battery was drained by the horn, causing these electrical gremlins? disconnect battery, leave it 2 minutes, reattach - no errors come up on display. start the car, and drive it for 30 mins to charge the battery - with a large emergency fete horn we happen to have in case of emergency. Come home, pull up, try to turn the car off - no - wont turn off, key will come out, display still on, car wont turn off. plug in my icarsoft and get 12 error codes P1111 unbdefined, p0111 P0135 P0130 P0030 P1102 P0102 P0100 U0101 U0155 P1102 P0102. I remove the 2nd big fuse from the back of the fuse box under the bonnet to kill the car engine, does its job. Disconnect battery. leave a few mins, reconnect battery, error codes all gone, lock car. Come here hoping a wonderful person will take pity on me and offer some suggestions or solutions. PLEASE HELP!!

Thanks,

Jason

 

[samoht]

I don't know the answer, but one thing you could clarify - is your car petrol or diesel?

A "rain/hail shower" normally involves a thunderstorm, in which very large amounts of electricity are discharged - I do wonder if a lightning strike on/near the car has fried part of an ECU or similar? Sounds like more than just a short circuit of the horn, given the other symptoms.

Good luck, hopefully someone with similar experience will come along with the answer!

 

[bluejmc2005]

Thank you for taking the time to answer, it's a diesel. My daughters say no thunderstorms or lightning as far as they can tell

 

[Martin 1]

That's a symptom of the car burning it's own engine oil, very very nasty, though if pulling a fuse stopped it, it may not be. Star diagnoses needed immediately. It may be a water issue, but you can't guess. Good luck, let us know how you get on.

 

[MrGreedy]

I've read something similar on here in the past few months about someone not being able to stop the car, so have a search on the forum using the advanced search.

I'm thinking water ingress rather than lightening.
The horn/alarm module is often behind the front passenger wheel arch liner of Mercs, and is often susceptible to getting wet and shorting and causing errors. You could try disconnecting that to see if it is as fault, or pulling the alarm fuse if it's the only item on the fuse.

My other thoughts is where are the ECUs and SAMs on your car? Have you checked they are dry?

Also, have you had condensation inside your car in the past 12 months, indicating possible blocked drains causing overflow of water into the cabin?
Usual suspects are sunroof (don't know if you have a sunroof), scuttle drains under the windscreen wipers, aircon heater box lower drain exiting somewhere around the transmission, and rear boot and light seals.

 

[MrGreedy]

That's a symptom of the car burning it's own engine oil, very very nasty, though if pulling a fuse stopped it, it may not be. Star diagnoses needed immediately. It may be a water issue, but you can't guess. Good luck, let us know how you get on.

I agree with this, but I was working on the basis that if the fuse pull stopped it, it probably isn't a runaway diesel engine burning it's own oil.
But I also 100% agree, STAR diagnosis immediately is the way forward here.
You might need to get the car trailered to a specialist as probably the safest bet.

 

[markjay]

I don't suppose the car was serviced at an MB dealer within the previous 12 months by any chance? Because if it did, you'll have Mobilo cover and they'll come out to you with STAR.

 

[markjay]

Also, check the scuttle and the drain pipes. Also drains in the doors and around the boot. Blocked drains (mud/leaves) can cause flooding of electrical components, most notably the SAMs.

 

[markjay]

And last, there may be two issues here. The horn, and the unstoppable engine, might be one. But having all the warning lights on the dash come-on after disconnecting the battery could be normal behaviour and not in itself part of the original problem.

 

[samoht]

One possibility could be that a short circuit made the ignition live (as if you put the key in the 'on' position), and the alarm saw the car being 'started' without the key authenticating, and so triggered? That could possibly explain both the horn and the unstoppable engine.

 

[bluejmc2005]

Thank you all for your replies. I stepped away from the car last night as 1 - it was dark 2 - it was torrential rain and 3 : I'd had a fair amount to drink!

Firstly, I cannot thank those ifnyf you who have replied enough. I'll be joing this site and supporting it that's for sure.

I'm trying to work on the principle that the simplist solution is usually the correct one. There were no issues with the car that I knew of prior to the heavy rain. It rains heavily, issues begin. The alarm was not triggered, just the horn. In fact when I first returned home the car seemed to be unaware there was an issue with the horn and was working quite happily save the horn. I'm yhetfore going to begin with the assumption that the horn shorted/got wet and that caused the continuous noise. I've removed the fuse for that and the horn ceased. Now, the rest of the issues perplex me; could it be that whilst removing said fuse in my haste to prevent the neighbours rioting I was not as careful as I should have been and water got inyo the fuse box under the bonnet? Possibly, whilst my wife held an umbrella as I did it I know from experience that mere drops of water can cause havoc with electrics so the first thing I'll do later this morning when the rain stops is remove each fuse from th fuse box and make sure all are dry. Battery is already disconnected as I wanted to prevent any further damage. After I've done that, I'll check all the drains (if I can find a chart of where they are in my 2010 CLS) and then I'll find the actual horn itself and see if that provides any clues. I'll update here with any success or failure.
Again thank you so much for your help and please do keep the ideas coming!

 

[MrGreedy]

As for leaks from drains, get the boot liner out and check for damp, and inside the car check all the carpets

 

[bluejmc2005]

So the drain under windscreen fuse box side was clogged with loads of muck, my working theory is that meant the rain had nowhere to go so pooled and feel in the fuse box some how

 

[bluejmc2005]

Don't see any leaks or evidence of leaks anywhere else, and the fuse box seems dry

 

[bluejmc2005]

The SAM unit it housed with the fuses under the bonnet I think? I have this morning inspected the fuse box area, I cant see any evidence of water ingress etc. I started the car this morning to no error messages, it powered down as it should, I drove it briefly (no horn) again powered down as it should. I looked at the horn, nothing obvious but seems reasonably simple to bolt on and off. Put the fuse back in for the horn, tried the horn and worked 2 our of 7 times, the other times it tried to make sound but failed. So I think the horn needs replacing. I have removed the fuse for it again and will order a replacement horn, wont drive it until that arrives. I cleared all the water escapes I can see, as I say the one above the fuse box was clogged everywhere else seemed fine no evidence of water anywhere

 

[Martin 1]

Good news so far, I'd still get Star to read off any codes.

 

[bluejmc2005]

Yep will be doing that tomorrow

 

[Martin 1]

Fingers firmly crossed.

 

[Dichtung]

Could it be water in the EIS (ignition switch)

 

[bluejmc2005]

Star showed nothing live, same codes I reported earlier as historical. No issues this morning when driving to garage, no errors etc, fingers crossed it was a temporary blip caused by rain ingress to that fuse box due to the blocked water escape