It’s unlikely to survive fixed directly to the hot cat and (the Anazon alarm) is not sensitive enough to trigger when fitted to the chassis. However, strapped to the rear silencer bracket (a cooler part of the system), I found it sensitive enough to be triggered by a tap on the engine manifold cover.
Although powered by 3 small batteries, those of a more adventurous nature could easily convert this to be powered from the car battery via a 12v to 5 V converter - no need to crawl under the car to change batteries. You could also add a flashing LED to re-inforce the deterrent.
Like many of these things, you may only find out if it works when it doesn’t.
MX5 Restorer near Hastings have Alu Plates that fit under the car, see link below. I can’t seem to find a MK3 version but the 1st cat would be very difficult to remove, the one under the car I’m not so sure about.
Would there be any advantage in configuring one of these to the nearby chassis rails perhaps for extra chassis bracing?
It might not need to be solid, an X-ways long lattice could brace, block access and still be a time waster for the t-leaf while allowing MOT inspection.
I started with a similar concept but thought the tilt angle required to close the contacts seemed too high. Looks like you give the switch a pre-set offset - I didn’t think of that . How high does the sill need to be lifted to trigger the alarm?
I presume you’re expecting a jack lift at the passenger side. I’m trying to figure out how two switches might be used (most seem to be bi-directional i.e +/- x deg)
Do you use a timer to switch off the alarm to meet the noise regulations?
(in reply to Bob_M1, post 3) - Yeah, I thought I probably should. It is a genuine post with good and helpful intent, so I thought that not everyone would share my sense of humour about next doors cat vandalising my roof.
Just a nudge on the car is enough to make it tweet. Lift the car an inch or so and a continuous alarm is heard. No cut off if it happens whilst I’m out, didn’t think of that. Car is parked with the near side fairly tight to the wall. Alarm more for any attempt to fiddle at night whilst I sleep in the room above with a window open.
That just looks like you’re going to lose any extra £150 when the thieves use an angle grinder to cut a big hole in the cat guard. The only upside is when they do the dust produced is toxic.
Nice for The Mx5 restorer to try and help out though but they said it’s specifically to fend off attacks from saws rather than grinders.
You can use a fibre disc (they create no sparks) and it will massively reduce the clogging effect.
At least in the cities, these people don’t care for noise. They are the same people stealing motorcycles in broad daylight, who just causally cut 20mm links on security chains and push the bike home.
It’s an okay deterrent but like said if they want it they will get it. Come back 2 weeks later and finish of the cat guard.
Best solution is just buy a modern cat and sell your original.
It’s only really MK2 that has the precious metals, MK1 cats get stolen but they are not worth much but then some thieves are not clued up and just opportunistic.
Thanks guys, sounds like I’ll leave my MK3.5 as is and take the chance. I’ve got other upgrades in mind, I’ll get on with those.
On the cutting disk/Alu plate front, yup, all you can hope to do is deter and potentially slow them up. Why would a crook bother if they can find an easier steel.
An alarm on the other hand typically gets ignored by all but the owner if it’s a quick steel so slowing is the key in my view.
The crooks simply don’t care and if caught just get told off … ‘you naughty little crooks, don’t do it again … pretty please’
I started with a similar concept but thought the tilt angle required to close the contacts seemed too high. Looks like you give the switch a pre-set offset - I didn’t think of that 
. How high does the sill need to be lifted to trigger the alarm?
