2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off!

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Mon 28 Jun 2021 10:14
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - carnut1980

Hi all, if i lock my car with the fob, the alarm WILL go off, within 5 minutes, it is the 'beep beep beep' of the horn!

Now the horn doesn't work, not when you press the steering wheel, but the horn unit itself DOES work, with infra red steering aid (fitted but removable) so passes MOT etc!

I can't help but think that the 2 issues are related?

All windows are shut, boot/bonnet are shut!

I can switch off the internal motion sensor,, but has no effect, the alarm WILL go off, unless i lock with key blade, which is kind of annoying!

The 'break glass' sensor in the boot, is intact, as is its wiring!

No lights on dash, full history, 110k miles!

Any ideas why the alarm keeps getting triggered?

cheers

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Mon 28 Jun 2021 10:44
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - Heidfirst

it could be as simple as a low 12V battery.

As you say, if you lock the car with the mechanical key it won't set the alarm.

Edited by Heidfirst on 28/06/2021 at 10:46

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Mon 28 Jun 2021 11:02
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - carnut1980

yes but, i want a solution!

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Mon 28 Jun 2021 11:30
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - elekie&a/c doctor
If an alarm goes off soon after shutting the car , that’s often an indication that the system has detected something not shut properly. Could be bonnet switch. I would assume the circuit to the horn from the original push has been modified to accommodate the disability controls . Possibly the main alarm siren is faulty. Back up battery dead ?

Edited by elekie&a/c doctor on 28/06/2021 at 11:37

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Thu 1 Jul 2021 21:01
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - carnut1980

Exactly where in the boot, is the glass break sensor? As i am happy with the 12v battery, i will try the GB sensor first, then i will check out the disc horn!

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Thu 8 Jul 2021 11:06
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - carnut1980

when you say 'back up battery in main siren is dead', do you mean the disc horn?

As the alarm is basically a 'beep beep' of the horn, but the disc horn doesn't have a back up battery!

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Thu 8 Jul 2021 12:27
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - elekie&a/c doctor
Most cars with an alarm system have a battery back up sounder as well as the regular horn. Yours may be different. I would investigate wether this model has such a system fitted .
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Fri 9 Jul 2021 12:55
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - carnut1980

Yes, apparently it also has a siren (that sounds identical to horn) PN 89040 12010

Would disconnecting or removing this part, stop the flashing of the lights, as well as the audible alarm though?

cheers

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Fri 9 Jul 2021 13:52
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - elekie&a/c doctor
Very possibly. You need to disconnect it to try it . Don’t know where it is , but likely to be hidden away somewhere behind some trim panelling.
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Mon 28 Jun 2021 18:46
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - Heidfirst

yes but, i want a solution!

How old is the 12V battery? 1 of the things that usually is a trigger for a car alarm is voltage drop - it's meant for detecting when e.g. an interior light goes on when a door opens but an ageing battery can also do it.

If it is a failing 12V battery that is the cause then the solution is obvious.

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Mon 28 Jun 2021 21:11
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - carnut1980

Battery is not the original, all electrics work fine, car starts first time, every time, and gets plenty of usage! I suspect faulty contacts for horn circuit, within the SW, and i suspect this MAY be triggering the alarm, which ALWAYS goes off, within 5 min of locking car with fob!

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Mon 28 Jun 2021 21:14
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - carnut1980

I did check 12v battery with a multimeter a week ago, was showing 12.71 V, which should be adequate, no?

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Mon 28 Jun 2021 21:16
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - madf

The 12V battery does not power the starter motor, it only powers the electronics to control the main battery.

You need firstly to check 12V battery voltage. Under 12.4V = FUBAR .First.

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Mon 28 Jun 2021 21:29
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - carnut1980

12.71V, as stated, but i will check it weekly!

Meanwhile, is removing an airbagged SW any different on a hybrid? A few screws in the rear pillars still?

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Sun 19 Sep 2021 20:49
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - carnut1980

UPDATE! PROBLEM IS SORTED! was the bonnet sensor switch that was the issue! I disconnected it, no more issues, no lights or message on dash! When i opened bonnet before, it would still remain 'flush', it wouldn't pop up a little, which is what made me suspicious of it!

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Sun 19 Sep 2021 22:49
2012 Toyota auris 1.8 hybrid! - Toyota horn doesn't work, alarm keeps going off! - Brit_in_Germany

As elekie suggested 3 months ago then.

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