Car circuit question, Land Rover antitheft device

Thread Starter

Msipos0911

Joined Jul 27, 2020
13
My Land Rover antitheft device on fritz. Key wont turn. I can pull fuse 18 and put back in and get one start as system resets. I was thinking of a way to automatically do this by connecting some relay from the car lighting fuse circuit to fuse 18 that closes fuse 18 circuit when lights go on and opens it when lights go off. Know of a DC relay that would do that? I could just hook up a toggle switch to fuse 18 but was looking for something cleaner and automatic.
 

Hymie

Joined Mar 30, 2018
1,079
This could be achieved by wiring a 12V relay coil across the ignition circuit, but rather than taking the 0V straight to the chassis – connected it via a capacitor of around 1,000µF.
Then wire the relay normally closed contacts in series with fuse 18.

In operation, when the ignition circuit is initially powered the relay will momentarily energise as the 1,000 µF capacitor charges – once charged, the relay will drop out. When the ignition is switched off, the capacitor will discharge through the ignition circuit load, ready to charge again when the ignition is switched on again.
 
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Thread Starter

Msipos0911

Joined Jul 27, 2020
13
This could be achieved by wiring a 12V relay coil across the ignition circuit, but rather than taking the 0V straight to the chassis – connected it via a capacitor of around 1,000µF.
Then wire the relay normally closed contacts in series with fuse 18.

In operation, when the ignition circuit is initially powered the relay will momentarily energise as the 1,000 µF charges – once charged, the relay will drop out. When the ignition is switched off, the capacitor will discharge through the ignition circuit load, ready to charge again when the ignition is switched on again.
So fuse 18 gets shut down after ignition on and back online when ignition shut off? Only potential issue is whether thats a problem while driving. I was looking to rig to circuit on when ignition off like interior lights.
 

Hymie

Joined Mar 30, 2018
1,079
No, the relay is only energised for around 1 second (each time the ignition is switched on), the circuit in fuse 18 is momentarily opened, as required – to reset the anti-theft device.
 

Hymie

Joined Mar 30, 2018
1,079
You could wire the relay in the cabin lighting circuit without the need for the capacitor in the 0V line. But opening the vehicle door (or any other action causing the interior light to come on) would result in the fuse 18 circuit being de-energised. This might cause problems depending whatever is powered via this fuse.

By using the capacitor/ignition circuit relay, the fuse 18 circuit is only momentarily open circuited each time the ignition is initially powered.
 

Thread Starter

Msipos0911

Joined Jul 27, 2020
13
You could wire the relay in the cabin lighting circuit without the need for the capacitor in the 0V line. But opening the vehicle door (or any other action causing the interior light to come on) would result in the fuse 18 circuit being de-energised. This might cause problems depending whatever is powered via this fuse.

By using the capacitor/ignition circuit relay, the fuse 18 circuit is only momentarily open circuited each time the ignition is initially powered.
That should be ok as it resets the security system same way as pulling fuse waiting few seconds and replacing would. Just worried one second may not be enough. How could i do this all internal to fuse box?
 

bwilliams60

Joined Nov 18, 2012
1,430
Rather than try to bypass the security system, why not get it fixed properly and probably cheaper? Is the security light on? It sounds like your keys need to be relearned or reset as the controller is not recognizing them? Any codes that you know of?
 

Thread Starter

Msipos0911

Joined Jul 27, 2020
13
Rather than try to bypass the security system, why not get it fixed properly and probably cheaper? Is the security light on? It sounds like your keys need to be relearned or reset as the controller is not recognizing them? Any codes that you know of?
Old Land Rover. Not the keys. I pull fuse 18 and replace starts once. Land rover got rid of locking steering wheel in 07 with all the problems. Used part is a grand. Looking for something automatic vs what i found on net showing attaching toggle switch to fuse 18. I would think it a simple circuit between fuse 18 and lighting circuit with relay of some sort.
 

Hymie

Joined Mar 30, 2018
1,079
You could pull fuse 18 for around 1 second to see if the anti-theft device was reset.

If a longer time is required, you could increase the value of the 1,000µF, maybe using a super-capacitor of 10,000 µF (16V).

You will need to trace fuse 18 wiring and break into it, wiring the circuit via the normally closed relay contacts.
 

Thread Starter

Msipos0911

Joined Jul 27, 2020
13
You could pull fuse 18 for around 1 second to see if the anti-theft device was reset.

If a longer time is required, you could increase the value of the 1,000µF, maybe using a super-capacitor of 10,000 µF (16V).

You will need to trace fuse 18 wiring and break into it, wiring the circuit via the normally closed relay contacts.
Nothing i could do just in the fuse box area? Its in the glove box so plenty of room.
 

Hymie

Joined Mar 30, 2018
1,079
You could get hold of a spare low current fuse (that fits in the fuse holder) and see whether it would be a simple matter to modify it – securely connecting a wire to each blade, bringing them out to the relay.

You could then blow the low current fuse and wire in the normally closed relay contacts. Having bypassed the fuse, you would need to add a fuse of the same rating (as fuse 18) in the wiring to the relay contacts.

You would also need to pick up the +ignition voltage and the chassis to wire to the relay coil and capacitor.
 

Thread Starter

Msipos0911

Joined Jul 27, 2020
13
You could get hold of a spare low current fuse (that fits in the fuse holder) and see whether it would be a simple matter to modify it – securely connecting a wire to each blade, bringing them out to the relay.

You could then blow the low current fuse and wire in the normally closed relay contacts. Having bypassed the fuse, you would need to add a fuse of the same rating (as fuse 18) in the wiring to the relay contacts.

You would also need to pick up the +ignition voltage and the chassis to wire to the relay coil and capacitor.
So i would have to test if while car running pulling fuse 18 and replacing doesnt impact something. Antitheft may shut down car. If so i would need to go to lights scenario where circuit broken with cabin lights on...presumably only when car off. I could do the fuse box wiring all in glove box using line from light fuse to relay to fuse 18 slot with inline fuse right?
 

Hymie

Joined Mar 30, 2018
1,079
If pulling fuse 18 causes no problems at all – then the simplest solution would be to wire the relay coil in the cabin light circuit. If the door was opened or the interior lights switched on then no problem would arise.

But if power to the fuse 18 circuit needs to be maintained – then the relay coil/capacitor solution is the way to go – providing a momentary loss of power to the fuse 18 circuit each time the ignition is powered.
 

Thread Starter

Msipos0911

Joined Jul 27, 2020
13
If pulling fuse 18 causes no problems at all – then the simplest solution would be to wire the relay coil in the cabin light circuit. If the door was opened or the interior lights switched on then no problem would arise.

But if power to the fuse 18 circuit needs to be maintained – then the relay coil/capacitor solution is the way to go – providing a momentary loss of power to the fuse 18 circuit each time the ignition is powered.
I will try starting the car and pulling fuse 18
 

Thread Starter

Msipos0911

Joined Jul 27, 2020
13
Sometimes not too much..
What year/model is it? I'm not all too sure what your problem is. There are many things that can cause no start. What does fuse #18 go too?
05 land rover hse. Google key wont turn fuse 18. When u put key in sensor tells wheel to unlock. Mine is unlicked so i suspect burnt motor that controls pin in steering column or controller. Since controller doesnt send back wheel unlocked key wont turn. Fuse 18 is immobiluzer in steering column. Pulling it and resetting reboots system allowing one key turn. Land river got rid of the mess in 07.
 

narkeleptk

Joined Mar 11, 2019
545
Oh, I see. Yes its common the motors go out on all types of makes/models with electric wheel locks. You are very lucky it failed in unlock, else its a pita to remove.

Personally I would just replace the motor or use a emulator both are cheap. Much better solution then what you been discussing in the thread.
 
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