Hi Guys

have a 1994 SWB Defender 300TDi

Thinking of using a hidden switch to act as a simple electrical immobiliser

Any thoughts/advice on the most sensible electric circuit to 'interrupt'?

Had thought of starter solonoid, but would not prevent bump starting if someone were feeling strong!

Cheers

Many thanks

A possible

Was thinking more along the lines if using an unused existing switch (heated rear window) to interrupt a circuit

Any other ideas?

The only "engine electrics" that relate to starting/running to my knowledge on early 300TDis are starter and stop solenoids (plus obviously oil pressure & water temp sensors).....so I'd hazard a guess that the best way of doing it would be a battery isolator. Could obviously change the crank position of the keyswitch to an unused switch as you say, just make sure you use a relay!

depends if its fly by wire or a good old solonoid and cable?

why ??? you can get a Thatcham cat 2 Imobiliser supplied and fitted for less than £100. so why arse about with switches, a thief will feel around for a switch or switch the others on if he is trying to nick it.
For less than £100 you can get the real deal thats why so many defenders are stolen NOT ENOUGH PROPER SECURTIY DEVICES FITTED.

Thanks guys

Good food for thought

Was also looking into a Cobra Immobiliser as a less 'heath robinson' approach!

I've got a hidden switch in the feed to the stop solenoid. While it won't stop someone picking up the Landy and taking it away on the back of a lorry, it'll slow down/stop the casual thief. Most of the time my Landy is outside my bedroom window, so if I hear someone turning the engine over and over, I've got plenty of time to get dressed, have a cup of tea, and then go and introduce myself.

Good man!

For my TD5, I plan to use an old technique I used a few years ago.

All you will need is a normally open reed switch. My plan is to cut the wire between the ECM under the driver seat and the Crankshaft Position Sensor, then I'll solder in my reed switch. The reed switch will be concealed somewhere and the engine will only start once a magnet is placed strategically in the correct position, to close the switch. Although this will not prevent it being towed away or lifted, there aint no-one who is gonna start it without a magnet.

My original technique from years ago was to use the reed switch (discreetly tucked in the corner of windscreen) which would control a relay which in turn powered an alarm and immobiliser. You could not get into the vehicle without a magnet or all hell would break loose in a cacophony of sound, but even if you were brass necked enough to brave the racket, the engine would never go without having used the magnet anyway.

The simple addition of a mercury tilt switch would help to protect it from being loaded onto a flat-bed, but I never went that far - maybe with the Landy though.

Clanforbes said:

For my TD5, I plan to use an old technique I used a few years ago.

All you will need is a normally open reed switch. My plan is to cut the wire between the ECM under the driver seat and the Crankshaft Position Sensor, then I'll solder in my reed switch. The reed switch will be concealed somewhere and the engine will only start once a magnet is placed strategically in the correct position, to close the switch. Although this will not prevent it being towed away or lifted, there aint no-one who is gonna start it without a magnet.

My original technique from years ago was to use the reed switch (discreetly tucked in the corner of windscreen) which would control a relay which in turn powered an alarm and immobiliser. You could not get into the vehicle without a magnet or all hell would break loose in a cacophony of sound, but even if you were brass necked enough to brave the racket, the engine would never go without having used the magnet anyway.

The simple addition of a mercury tilt switch would help to protect it from being loaded onto a flat-bed, but I never went that far - maybe with the Landy though.

Click to expand...

I was going to do something similar to your reed switch idea on the Escort, but was concerned about signal noise - did you not have this issue? Suppose it'd be exacerbated in my plan due to planning on using relays, but a strong magnet would probably affect it slightly I would have thought?

My cheapskate behaviour continues - I fitted a flashing red LED to my dash as a pretend alarm.

instantsquid said:

My cheapskate behaviour continues - I fitted a flashing red LED to my dash as a pretend alarm.

Click to expand...

Yeah, I have one of them too. The ends off an old analogue tv aerial plug when stuck to a small plastic box also looks very much like a motion sensor if located in full view and in an obvious place. Stick a wee led in the box so it flashes and looks like it's doing something. Even one of those kids headbands with different coloured LED's then it really looks the part. Have one "sensor" pointing one way and another one on the side pointing at 90° so it looks like it's "scanning" the whole interior.

TheKeymeister said:

I was going to do something similar to your reed switch idea on the Escort, but was concerned about signal noise - did you not have this issue? Suppose it'd be exacerbated in my plan due to planning on using relays, but a strong magnet would probably affect it slightly I would have thought?

Click to expand...

Funnily enough, it was on an Escort (my works van) that I'd done this. In that case I did use a relay (or two if I remember correctly, coz I had it doing all sorts of things.) I don't really think the signal will be too badly affected by the magnet (you don't need a dirty great big strong one for a reed switch, I'd need to check, but I think even the magnetic strip stuff they use to hold fridge doors closed is sufficient, though maybe not through thick glass) as long as you either use screened wire if extending the original cable or don't extend the original too much. The way I look at it, the original is running in a loom which has all sorts of signals and power flying about and this is the only one that is screened, so obviously it needs screening but I think because it's such a small signal from the CKP sensor and if that was the case then, yes, a nice little relay (changeover or latching) to do the job would be better, using the reed switch to trip it which means the reed switch could be located anywhere. A simple brush of your hand (holding said magnet) against the bodywork or window as you approach/leave the car would look so innocent to anyone who might be watching you. Stick the reed switch in the corner of your windscreen with a small security device warning sticker to hide it from the outside and it simply looks as if you happened to put your hand out as you walked up to the car.

Just to complete the thread, took the advice and fitted a Cobra 8510 immobilser alongside a clutch claw and disklock.

Will have to do for now!

Thanks all for the replies

all you needs a bench vice a 12 bore and a piece a string. job done. and if anyone tries to get in then its just a tragic suicide

I noticed in the news the other day SAS use attack Alsations. They strap them to their backs, abseil down from the roof, blow the windows in and then throw the dogs in first. They must be mean animals. Wonder if you can get them from an ex-military hard-wear dealer.

Surely since anyone with the smallest amount of Defender knowledge will be able to bypass any immobiliser and start the car from underneath it with nothing more than a couple of lengths of wire and crocodile clips, I don't think there's much point in it.

Later models with ECUs and all perhaps, but for the old fashioned engines it's all too easy to bypass.