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Steff
Trainee


Joined: 16 Jan 2015
Posts: 91



PostPosted: Thu May 10, 2018 9:20 am    Post subject: horn sounding on its own Reply with quote

Hi All,

While at work on Monday I got a call from reception saying that my alarm was going off.

I went out and all was silent, no indicator flashing so just unlocked, locked and went back to my desk.

No one at work would no it was mine (daily driver is a company volvo) except for one engineering colleague (who also happens to have a 930 turbo in his garage awaiting restoration) so I messaged him.

He said it didn't sound like a normal alarm sound, more like the horn sounding intermittently over a short period and then sounding continuously for a while before going silent.

Since having the car I have always felt the horn is a bit sensitive, being easy to make it sound unintentionally.

I looked at the fuse with the intention of just removing it for now to ensure it didn't happen again and found the fuse wire broken. I put the spare fuse in and couldn't make the horn sound.

It had an MOT a few weeks ago so can only assume it worked then.

So, whats happened? is there some sort of dodgy connection causing the horn to sound randomly and then the continuous sounding has caused the fuse to blow? if so, I'm guessing I just need a new horn unit, any suggestions for the dodgy connection?

many thanks
Steff
 
  
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alex yates
Brands Hatch
Brands Hatch


Joined: 06 Mar 2014
Posts: 14468
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Thu May 10, 2018 9:49 am    Post subject: Reply with quote

Your alarm also has a separate horn. Maybe it was that going off.
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2000 Manual 996 C4 Arctic Silver Convertible


 
  
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wasz
Magny-Cours


Joined: 28 Dec 2012
Posts: 2639


1999 Porsche 996 Carrera 2

PostPosted: Thu May 10, 2018 10:09 am    Post subject: Reply with quote

common problem with the 4 spoke wheel fitted to early 996

https://rennlist.com/forums/996-forum/485918-horn-problem.html

https://www.renntech.org/forums/topic/1728-horn-problem/?tab=comments#comment-11274

check these bushes and the horn relay and fuse

try hooking the horn directly to 12v to see if its blown, they do rust away

the alarm is a siren rather than horn, well my my99 is anyway
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alex yates
Brands Hatch
Brands Hatch


Joined: 06 Mar 2014
Posts: 14468
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Thu May 10, 2018 10:14 am    Post subject: Reply with quote

The alarm has a siren and a horn. Alarm your car with the boot or centre glovebox open and you'll hear it beep.
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Steff
Trainee


Joined: 16 Jan 2015
Posts: 91



PostPosted: Thu May 10, 2018 12:53 pm    Post subject: Reply with quote

ok cool. thanks both
 
  
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IanG1
Trainee


Joined: 08 Jan 2016
Posts: 98



PostPosted: Thu May 10, 2018 5:22 pm    Post subject: Reply with quote

It's the steering wheel, mine started doing the same while stood on the tipec area at last week's Donington Historic. Also does it under hard braking.
 
  
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stucart
Montreal


Joined: 24 Apr 2013
Posts: 501
Location: staffordshire 07 997 C4S


PostPosted: Thu May 10, 2018 6:56 pm    Post subject: Reply with quote

I had a similar fault but on my 997, horn went off on its own in the middle of the night! When got to it it had stopped? After that the horn wouldn’t work at all, took it OPC and initially it baffled them, they replaced both horns and that cured it. Hope that might be of some use perhaps.
ps. The car only had one horn working prior to this, that had been picked up at its last service but I hadn’t got around to booking it it as it was sorned over winter, the lone horn worked till it went off on its own then the above.
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deMort
Zolder


Joined: 21 Mar 2015
Posts: 5520
Location: Brighton


PostPosted: Thu May 10, 2018 7:46 pm    Post subject: Reply with quote

Do me a favour .. check under the passenger seat ... make sure theres no water bottles or that its wet under there .. if all good then perhaps the horn . steering wheel contact.

My reason ..

The alarm horn beeps and will do in an alarm trigger which fits the description .. the siren should go off but didnt hence im wondering water ingress to the alarm control unit .

It has a horn and a siren for the UK only markets .. horn is fitted to the o/s of the battery and on the brake servo bracket ... its for the CAT rateing at the time .
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Steff
Trainee


Joined: 16 Jan 2015
Posts: 91



PostPosted: Fri May 11, 2018 10:43 am    Post subject: Reply with quote

Thanks all,

Will check for water ingress but pretty sure its ok and having now read up on the contacts/steering wheel issue it sounds very likely that's it.
 
  
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searider
Silverstone


Joined: 07 Feb 2013
Posts: 140
Location: Southampton


PostPosted: Fri Jul 27, 2018 9:43 am    Post subject: Reply with quote

Right chaps,

I had this problem. Call from work to say that the horn had been going off all on its own and then stopped.

I did the washer repair on the airbag frame last night and replaced the frame, which had blown.

Still no horn.

The instrument displays dim a little when I press the steering wheel - so there's a load being taken somewhere.

Where does the horn relay live - that's my next thing to check.

Cheers
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deMort
Zolder


Joined: 21 Mar 2015
Posts: 5520
Location: Brighton


PostPosted: Fri Jul 27, 2018 7:01 pm    Post subject: Reply with quote

I guessed at a 2002 model and the wiring diagrams are below.

Relay board is o/s/f and above the fuse board .

GP2 .. or any GP on a wiring diagram is an earth point with the number as the location .. an earth basically .

Brown wire.
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easttorks964cab
Silverstone


Joined: 02 Jun 2008
Posts: 149
Location: East Yorks


PostPosted: Sat Jul 28, 2018 2:57 pm    Post subject: Reply with quote

may I throw my two-penneth in? I had a similar problem with mine. The horn would sound under braking and also if you put any slight pressure on the horn. This was much worse in hot weather. It turned out to be the airbag bracket. This has a couple of rubber bushes on it, that you are pressing against when you push the horn. These become worn and, in hot weather, soft, so there is less resistance against the horn.

Its is a cheap part and quick fix. Its worth considering.

hope this either helps the OP, or someone else with similar problems.
 
  
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Thomp1983
Silverstone


Joined: 26 Oct 2017
Posts: 139



PostPosted: Sat Jul 28, 2018 7:37 pm    Post subject: Reply with quote

If it's the black standard 4 spoke wheel you've got I've got a known working one under the bed you can have including airbag
 
  
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searider
Silverstone


Joined: 07 Feb 2013
Posts: 140
Location: Southampton


PostPosted: Sat Jul 28, 2018 9:27 pm    Post subject: Reply with quote

deMort wrote:
I guessed at a 2002 model and the wiring diagrams are below.

Relay board is o/s/f and above the fuse board .

GP2 .. or any GP on a wiring diagram is an earth point with the number as the location .. an earth basically .

Brown wire.


Thanks, mines a 1998, I’ll have a look.
I assume that if I can hear the relay clicking it’s ok?
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searider
Silverstone


Joined: 07 Feb 2013
Posts: 140
Location: Southampton


PostPosted: Sun Jul 29, 2018 11:59 am    Post subject: Reply with quote

Thomp1983 wrote:
If it's the black standard 4 spoke wheel you've got I've got a known working one under the bed you can have including airbag


PM sent re wheel.
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deMort
Zolder


Joined: 21 Mar 2015
Posts: 5520
Location: Brighton


PostPosted: Tue Jul 31, 2018 7:39 pm    Post subject: Reply with quote

searider wrote:
deMort wrote:
I guessed at a 2002 model and the wiring diagrams are below.

Relay board is o/s/f and above the fuse board .

GP2 .. or any GP on a wiring diagram is an earth point with the number as the location .. an earth basically .

Brown wire.


Thanks, mines a 1998, I’ll have a look.
I assume that if I can hear the relay clicking it’s ok?


Erm .. no .

It may click but if the contacts inside the relay are burnt it wont make the connection between 30 and 87 .

You should have 12 volts on term 86 with the earth on 85 only there with the horn pressed .

term 30 will be 12 volts with term 87 being the output to the horn .. if you bridge term 30 and 87 with a bit of wire then the horn should work ..
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searider
Silverstone


Joined: 07 Feb 2013
Posts: 140
Location: Southampton


PostPosted: Tue Nov 13, 2018 2:36 pm    Post subject: Reply with quote

deMort wrote:
searider wrote:
deMort wrote:
I guessed at a 2002 model and the wiring diagrams are below.

Relay board is o/s/f and above the fuse board .

GP2 .. or any GP on a wiring diagram is an earth point with the number as the location .. an earth basically .

Brown wire.


Thanks, mines a 1998, I’ll have a look.
I assume that if I can hear the relay clicking it’s ok?


Erm .. no .

It may click but if the contacts inside the relay are burnt it wont make the connection between 30 and 87 .

You should have 12 volts on term 86 with the earth on 85 only there with the horn pressed .

term 30 will be 12 volts with term 87 being the output to the horn .. if you bridge term 30 and 87 with a bit of wire then the horn should work ..


Thanks all,

To close this out I changed the relay which made no difference.
Two new horns and the problem is sorted.

Duncan
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