02 Defender TD5 - Volumetric Sensor

Past couple days I have had a minor issue with my alarm on my Fender, started when I got home on Sunday.

If I press lock on the fob, I get a mis-lock error. Horn beeps twice, no hazards come on. However the engine is immobilised and the alarm is armed and goes off if I try to start it without unlocking it, same if I try and lift the bonnet. Though it does not go off if I open any of the doors and my interior light stays on unless I manually switch it off.

Plugged in me Nanocom, no errors on the main screen but under the alarm error codes I got 'Volumetric sensor open' took a couple of tries to clear it. When cleared the interior light went off, try to lock with the fob. Same thing, horn beeps, no hazards, interior light back on.

To add none of the door sensors are connected, some of them arnt even there.

Any ideas? Turned the horn noise off with the Nanocome so I at least I can arm the alarm in peace.

Sounds like you may have a door switch wire shorted to chassis somewhere. Put the light switch onto the normal (door controlled) position so that the light comes on. If you leave it like this for something like 10 / 15 minutes then the light should go out if the timer circuit is working properly irrespective if you have any door switches fitted. The timer is designed to stop the battery going flat if you leave a door open. If it does turn off then you have eliminated the timer circuit and it is probably down to a shorted switch wire. Are you sure none of the disconnected door switch connectors. are touching the chassis inside the bulkhead pillars or rear door area?

Can't be certain but I will have a look. The ones from the rear have been removed and the ends taped up. Ill check the door ones.

I have always had issues with the interior light, the switch is so stiff sometimes you can't even move it! It also flickers like mad sometimes. Need to replace it..

Kwakerman said:

Sounds like you may have a door switch wire shorted to chassis somewhere. Put the light switch onto the normal (door controlled) position so that the light comes on. If you leave it like this for something like 10 / 15 minutes then the light should go out if the timer circuit is working properly irrespective if you have any door switches fitted. The timer is designed to stop the battery going flat if you leave a door open. If it does turn off then you have eliminated the timer circuit and it is probably down to a shorted switch wire. Are you sure none of the disconnected door switch connectors. are touching the chassis inside the bulkhead pillars or rear door area?

Click to expand...

So I have gone through and can't for the life of me find any of the cables! My 90 never came with the button things attached, so im guessing the cables are lost somewhere inside the depths of the landy....

Despite much fiddling and research I can't seem to turn off the door buttons with the Nanocom, which is upsetting.

Last port of call is to remove the alarm unit (going to do this anyway to solder on a relay so I can have central locking off the fob) and remove the wires from the source. Anyone know if this will have any adverse affects on the alarm system as whole? Depending on how it goes I may even replace/reinstall them, at least on the front doors.

Just seems totally random. 3 years and it has been 100% spot on, took me doors off, fitted central locking (never touch any LR systems in the process) and since then I keep getting the miss lock situation. Since then twice it has worked correctly... Good news however is the bonnet sensor does work! Popped it and the alarm went crazy so thats a plus...

I just feel slightly on edge leaving my 90 anywhere with 1 less layer of security, so much so I barely park out any more.

Slight update - I believe I have found the cause of the mis-lock situation. It appears to be coming from the passenger side door, I must have disturbed something when I took the door off and ran the central locking wiring. Not pinpointed the issue but I can get the alarm fully set if I slam the passenger door