I am planning on putting in a simple switch as an anti theft device… any suggestions where to wire it in to?
I had one of these on my old Mini Cooper. Didn’t stop the scum taking it for a spin and leaving it on blocks in Bristol.
But assuming you know that thieves are quite often nowhere near as stupid as they appear…personally I would break one of: the ignition feed to the ECU, any of the feeds to/from the CAS or coilpack, or maybe the fuel pump relay. Certain things will throw up an engine fault code if you forget to switch it off before trying to start it though.
I put one of these in once, in the coil feed line (not the best I know if I did it again it would be the fuel pump relay feed line) but I used a 7mm Jack plug and socket. That way I had a removeable ‘key’ to immobilise the vehicle.
A simple bridge wire soldered inside the male end completed the circuit 
I would say one thing…I got my mini back, minus its wheels, so it wasn’t all bad. My brother had an old Escort Mexico that had a great immobiliser, and the thieves got so annoyed at not being able to drive it away that they torched it instead. Not such a good investment for him. Ya takes yer chances I guess…
thanks guys, will i get any error codes if I put a switch in the fuel pump reley wire?
I’m not positive (if it did it would depend on what model we’re talking about) but I don’t think so. Certainly not if it’s a mk1.
I would be much more inclined to use a physical deterrent rather than than a sophisticated electrical one. It is obvious, even to the sort of person we would all like to break our feet kicking them. Car theives usually go elswhere when they see something painted bright yellow on the steering wheel. This whould save you from modifying the electrics in any way. These days starting a car without the key is very difficult, hence why these people break into your house first to steal the key. I always use a heavy duty steering wheel lock on my car when it is parked.
Regards Geoff Peace.
My main security will be a removed steering wheel! 
On that subject of torching things, did anyone else notice the front page of the free Metro paper during the riot season. It featured a red mk1 on fire which made me very sad indeed. then a few pages in, a much smaller picture of a white mk1 also very much on fire. Im still trying to recover, just too much to bear
even after all this time.
Thanks
all. I have fitted a switch into the fuel pump relay wiring, all seems to
be working fine. I will also be using a steering wheel lock, and a simple
alarm.<o:p></o:p>
There has been a spate of older cars going missing from my local
area in the last few months… first a K reg Honda Civic, and then a
1970’s Triumph 2000 of all things… Older stuff is easy to steal in comparison
to the new cars!<o:p></o:p>
I did have a removable steering wheel on my Caterham, but it
was a pain to carry around!<o:p></o:p>