kill switch

[eastona]

I had two windows smashed on my morris recently by mindless yobs. I also had an attempted theft of my MG around the same time. They would have got the MG through hotwiring the car, but fortunately it is pig to start (unlike the Morris ) and I don't think they used the choke.

Which brings me to my point. The morris has no steering lock and is pretty vulnerable, so I thought of fitting a cut out in the low tension circuit. Maybe a discreet switch next to the reversing light switch and using a relay to avoid having to run the actual LT cables all the way back to the cabin. I also thought of maybe an earth cut out switch. It wouldn't deter someone with time and a bit of nouse. Not sure I want to go to the hassle of removing the rotor arm every time I leave it, but habe thought of removing the brake master cylinder

I guess other than a pukka alarm nothing will help. Any thoughts or what have others done?

Andrew

[8009STEVE]

I have fitted a hidden switch which cuts the supply to the fuel pump. Tha car starts and runs for about 400 yards, then it runs out of fuel. The switch I used is a panel light switch, which is very small and hard to find.

[Rob_Jennings]

Two good solutions I have heard of is a hidden switch to:

kill the feed to the pump, so that it might start, but not run for long on the fuel in the carb

or

kill the feed to the coil, so they can crank all they want but its not going to start or run

both these have the advantage of not making the car look dead (such as a full isolation switch) which may prompt them to investigate, and a full isolation switch is very obvious

[alex_holden]

On my old moggy I fitted a hidden keyswitch under the dash which shorted the LT terminal on the distributor to the body. That had the effect that when the key switch was on, the points were permanently shorted to earth and the ignition wouldn't fire. So there was only one extra wire going to the engine (not as obvious to spot as a switch/relay spliced into the middle of an existing wire), and to bypass the immobiliser you needed to cut the wire rather than shorting the switch like you would normally do. One slight drawback: I did occasionally forget to turn the switch off and then wondered why I couldn't get the #@$!!# to start

[dp]

Just a thought but if fitting a switch to the fuel pump or to short the ignition, it isn't that hard to add another hidden switch or two to the circuit. It soon becomes habitual to switch them as part of the fire up procedure and slows down things much more for would-be thieves

[bmcecosse]

They thief could easily bypass the ignition cut out if they can't get it started. The beauty of the fuel pump cut-out is that the car appears to start and run ok - then conks out after about 50 yds - the thief will then be in an 'exposed' situation and will hopefully run off rather than start investigating why the car has ground to a halt.

[eastona]

Apart from now having glass in every window I discovered something new today. While poking around the car looking for somewhere to hide a sneak switch I found I already had a sneaky switch under the dash. Stripped out the glove compartment, fiddled around and found......a switch I never knew I had to turn the dash lights off not quite as cool as I first thought...but...if I permanently wire the dash lights on (I'm not too worried about being able to disable them) can I use that as a kill switch. Surely if I didn't know I had it (despite owning the car for nearly a year then it's pretty discreet?!

Andrew

[bmcecosse]

There has just been a long thread on here about this switch!! It's only designed for the wee dash lights - the fuel pump takes a fair current as it 'ticks' - that switch may not be man enough. Most just use a toggle switch and hide it somewhere not too obvious.

[eastona]

Must've missed that one .

You're right, it's a tiny tiny switch that probably only just copes with the lights.


Andrew
(reverting to plan A)

[NZJLY]

The other option (and I have been looking for the correct relay) is one where you have a push button switch that needs to be pushed to start the car, but once the circuit is running the relay keeps the circuit going. I think it is called a switching relay.
Once stopped the relay resets and so to start it you need to push the button again.
This makes it part of the startup. Else we tend to leave the kill switch turned off, as we become complacent.

I found the idea on another forum, but as yet I haven’t found a sparky that understands what I am talking about . I do live in hope though

[Alec]

Hello NZJLY,

that is very easy to do but requires a two or more pole relay.
The circuit must use the ignition feed, take an ignition fed supply, (white if you want it unfused, green if you want it fused) to the normally open contact on your push switch, then from the push switch to the coil of the relay, the other coil terminal is then connected to earth. With the ignition on, pushing the push button will bring the relay in. Now to retain that you need to connect one normally open pole of the relay across the push button. Now when you push the push button the relay retains itself via one pole, switch off the ignition and it will de-energise. Now all you have to do is use the other pole to interrupt the coil circuit.

Alec

[8009STEVE]

There has just been a long thread on here about this switch!! It's only designed for the wee dash lights - the fuel pump takes a fair current as it 'ticks' - that switch may not be man enough

I have ben using this switch for 3 years now

[alex_holden]

Alec, you don't need a double pole relay to do that. Simply put a SPST relay in the supply to the thing you want to isolate (coil or fuel pump) with a momentary action push switch in parallel with it, and power the relay coil from the output of the circuit. Pushing the button energises the coil, and the relay closes and keeps itself energised after you let go of the button. I would be a little worried about the possibility of it delatching when you don't want it to in a noisy car electrical environment though. Also the push switch needs to be capable of handling the current used by the thing the circuit is powering.

[Alec]

Hello Alex,

yes that will work but it is untidy from an electrical point of view,
My other car runs with a relay energised 100% of running time with no problems, by the way.

Alec

[alex_holden]

In what way is it untidy? It does the same thing with fewer parts. The only advantage I can see of a second pair of contacts is you can get away with a lower-specced push switch. The risk is that it could unlatch itself if the supply dips enough due to eg. operating the starter motor while the battery is low.

[Alec]

Hello Alex,

In industrial electrical circuits it is normal to segregate control and load, which is why i said it is untidy. The cost differenec between a sp and dp is negligible.

As I said my car has a relay energised all the time, and is essentila to the running of the car, (fuel pump) and it does not unlatch even while cranking. Hold in voltage requirement is much lower than pull in voltage.

Alec