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KiwiNCFC

Member Since: 14 Jul 2019
Location: East anglia
Posts: 47

300tdi Alarm and Horn sounding when reconnecting battery?

Hi guys,

Hoping someone can help, so my starter motor was constantly on after I started my landy the other day and after I turned it off there was still a racket coming from the engine so I quickly disconnected the battery and it stopped. When I reconnected again it arced so I left it disconnected and ordered a new starter motor.

A week later and the new starter fitted today and I reconnected the battery. Whilst tightening the battery connections (20 seconds or so) the horn started blaring then the alarm started going! I kept clicking my fob buttons but it didn't stop so I disconnected the battery again. Now everytime I connect the battery, horn and alarm just constantly sound! It's very irritating as I live on a quiet cul de sac and I can't really investigate further unless I somehow find the alarm and disconnect wires from the horn so I can fault find!

I'm a bit confused as I never use my fob button to set the alarm and only press it for the immobiliser and I have a spider bypass fitted years ago so I was very surprised when I started hearing an alarm as I though the spider disables that!

Could I ask for advice?

My battery is likely low in voltage 10-11v as it was draining it when the starter motor was stuck on so if the 'system' sees low voltage does it cause weird alarm issues like this? I've now stuck it on charge for a few hours and I will try to reconnect tomorrow morning to avoid annoying the neighbours!

I also thought about maybe it's because I was in my defender with the car doors/bonnet closed and the sensors detected me in there? If I'm honest I'm not quite sure how the immobiliser/alarm works re doors open/bonnet etc. I'd love someone to explain how it works, even though I thought I had a spider bypass fitted!

Thanks in advance!![/url]

25th Jan 2025 5:13pm

Mining Subsidence Stu

Member Since: 06 Mar 2024
Location: Cornwall
Posts: 29

1991 Defender 90 200 Tdi HT Caledonian Blue

It's a nightmare. Mine was playing silly

and I wired it out and the problem was the alarm. Take the 10A fuse out on the right top and it will shut that thing up. Mine would blow the 5A fuse below and did all sorts of funny things. I put a 7.5A fuse in and it worked, but it was always a matter of when it was going to cause problems.

I got rid of the truck and got a 200 as a replacement. I'd google how you find the OBD port and switch the alarm function off, per foreign trucks with no key fob.

It's a mystery

Mine would not crank occasionally.

3rd Feb 2025 6:28pm

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