DIY Car Immobiliser system ???

Connect a wire from the earthy side of your coil, through a switch, to an earth point on the car. Hide the switch, or use a key-switch you can get from Halfords.

Make sure you use the earthy side of the coil, when you close the switch it supresses the spark. Don't attempt this with electronic ignition circuits. That's what I use to do with my old ford, it worked for me YMMV

A better bet is to discourage the thieves from even trying with a large steering wheel lock, the disc type is best. cheap immobilisers are on ebay, but thieves of old cars won't be put off by that, this was proved to me a few months ago, the car was still there but wrecked around the steering column. I have never had an attempted theft on any of my vehicles with steering locks on, but at least four on vehicles without.

mrcheerful

I'd heard that at least on older cars you could remove the rotating head bit (don't know the technical name) of the distributor and so stop the car from starting. Comments?

Are there any other bits of the engine you could do this on? Clearly this isn't particularly convenient but may be useful if you'll be away for a week or two. Suppose it wouldn't stop damage from attempted theft.

Rob

My preferred antitheft technique is something like this:

Stomp on brake pedal, flick switch, all 4 wheels locked rather positively!

Simple methods: Petrol with carb - break switched +12v feed to anti-dieseling /stop solenoid on carb Diesel (mechanical pump) - break +12v feed to stop solenoid on pump Petrol/diesel with electric fuel pump - Break feed to fuel pump will probably splutter to a halt pretty rapidly. Older cars without stop solenoids/fuel pumps - muck around with the coil as described elsewhere in this thread. Petrol with single point injection - break connection to FI solenoid.

More sneaky: Petrol/Diesel with ECU - break connections between crank/TDC/engine speed sensor and ECU. Engine gets cranked, ECU cannot detect that the engine is turning, and so doesn't inject any fuel - car is immobilised. This isn't guaranteed to work - it might force the engine into "limp home" mode.

/john

The message from Rob Campbell contains these words:

Rotor arm. I'm not sure a '93 Astra has one.

He's already done that - he's got an Astra Saloon :-)

The message from "John Kenyon" contains these words:

Fun with older ignition systems is to switch out the capacitor. Engine usually starts - but won't run properly at all.

LOL :-)

Though it does in fact pose the problem that thieves know how easy it is to nick an Astra so will give it a go anyway ... Fitting a hidden switch/immobiliser isnt going to stop em breaking the doorlocks or smashing a window to have a go at starting it. A more visible deterrent would be a much better option.. Ie a steering/gearlever lock etc ..

A slightly bloodstained card on the dashboard with an appointment time written on it for the local communicable disease clinic can deter the wary too .. (well at least those who can read) :-)

Not in my trousers ( snipped-for-privacy@ddress.is.invalid) gurgled happily, sounding much like they were saying :

I'd have thought it preferable to *encourage* 'em to nick it...

Indeed. All you're going to have is a wrecked, useless car parked outside instead of there being no car.

Same outcome, just you get the hassle/expense of disposing of it.

How about splicing the starter motor wire to a hidden switch .

They would get the ignition and no power to the starter .

I reckon most neds would be too lazy to push it - assuming there was more than one .

Any chance of getting my hands on a rough sketch/drawing ??? Am pretty much of a novice when it comes to car maintenance, but am an aspiring young lad :)

If getting a sketch won't be possible, would appreciate it if you can point out which one would be the earthy side of the Ignition Coil Cable? (I presume the Ignition Coil Cable is the connector between the Distributor [where leads from all the spark plugs are brought in] and the point X [don't know what this is ... but thats where the other end of the Ignition Coil Cable goes])

Regards

Yes I'd agree with you but for that you are looking at spending around 80 quid.

Regards

Have a look here

In the fist diagram, the earthy side is where the switch circuits connects to on the primary coil. Do not touch the secondary which is the thick cable going to the distributor.

If you pull the earthy side of the coil to earth, it can't generate a spark when its switched. You can probably tell which is which with an AVO or a tourch bulb. The one that lights up when you connect the bulb between the car body and terminal is the live side (engine and ignition off for this)

The high currents would probably burn the switch out. The current is of the order of 100Amps

Martin (martin snipped-for-privacy@btinternet.com) gurgled happily, sounding much like they were saying :

The switching current between leading from key to solenoid isn't anywhere near that - switching the big wire from battery to starter would just be silly.

You would need to use REALLY thick wire anyway as you would need it to go round an adjacent fence post too to stop them pushing it away when they realise that the ignition comes on but the starter doesnt turn. :-)

true. SOR neglected to say which wire, I was assuming he meant the actual starter motor wire (as he said), not the solenoid switch

the point is that the car is likely to be left alone , the steering lock will easily transfer to your next vehicle too. eigthy quid is b all compared to the cost of a broken window, smashed ign switch and cowlings, which is the minimum a thief will do before discovering that there is an immobiliser.