Mystery alarm

[Alnwickist]

Background: Car not used for a week, parked on a driveway, cold weather (-2 to 0 degrees): horn started to blow continuously in the evening, no hazard lights activated. entered car using the key, inserted key in ignition, dashboard warning lamps came on but engine refused to start. Horn continued to blow and the only way to silence it was to disconnect the Battery.

Any thoughts or advice please.

Thank you

Jeremy 

[Hybrid21]

Sounds like your Battery could be flat Jeremy. Is it the original Battery ?

If so it's most likely needing replaced.

[Alnwickist]

Thank you for your prompt response Iain.

The car has covered around 45,000 miles. I bought it second-hand, so I don't know how old the Battery is. Would a 'dead' Battery cause the horn to blow continuously (i.e. not intermittently as when the alarm is triggered)?

[flash22]

20 minutes ago, Alnwickist said:

Thank you for your prompt response Iain.

The car has covered around 45,000 miles. I bought it second-hand, so I don't know how old the battery is. Would a 'dead' battery cause the horn to blow continuously (i.e. not intermittently as when the alarm is triggered)?

oh yes low voltage does strange things to electronics, Mk3 yaris will turn this headlights on with a low Battery, a cold snap with kill a weak Battery average life of a lead acid Battery is 5-6 years unless it's a Yuasa or Bosch/Varta what should last 10 years +

[Hybrid21]

Yes Jeremy, as per Bob's post 👍

[Alnwickist]

Many thanks to Iain and Bob, who were both right in their diagnoses. New Battery fitted - problem solved.