12v switch help

[Guesty2015]

Unknown if this is in right place but was stuck on where to put it
Im buying a eye catching car and worried about it bein nicked now it has a cat1 alarm
Im looking to fit a hidden switch to the fuel pump that need to be turned on to make the car run but the other thing im worried about is being car jacked cos im only slim built so was wanting to put a trip switch so i could wire it to the drivers door switch for the interior light so that when the car door opens it turns the switch off and kills the fuel supply

Does anybody know if such a switch exsits or it this just my mind thinking of such a switch

Cheers dave

[Doctor Volt]

And when they have thrown you out and shut the door the car will run again

Yes it can be done but not with a switch, you will need a switch and relays

If you want a diagram I will gladly knock one up and send it to you

[Doctor Volt]

Adding

There is a safety issue about your idea

[Doctor Volt]

Adding

Have you considered this - A car is just for getting from A to B and can easily be replaced with another car

Your life cant be replaced. If a nutcase decides to turf you out of your car to be able to steal it, that same nutcase may be capable of killing you if the car has been stopped from running

Is a car worth a life?

[Guesty2015]

No i mean when the door is opened the switch turns off and need to be turned back on via the hidden switch if you get me so like the pump will turn off they will floor the car and get about 40m and cut out then i get back in flick the hidden switch back on and drive away hopefully wont happen but its a risk i dont wana take cheers

[Doctor Volt]

Guesty2015 said:

No i mean when the door is opened the switch turns off and need to be turned back on via the hidden switch if you get me so like the pump will turn off they will floor the car and get about 40m and cut out then i get back in flick the hidden switch back on and drive away hopefully wont happen but its a risk i dont wana take cheers

No unfortunately it doesnt work like that with a fuel injected engine

Sorry I am taking it for granted that your eye catching car is fuel injected
If it is fuel injected - By switching off the fuel pump there will be no fuel pressure and the car wont move

[steveo3002]

Guesty2015 said:

No i mean when the door is opened the switch turns off and need to be turned back on via the hidden switch if you get me so like the pump will turn off they will floor the car and get about 40m and cut out then i get back in flick the hidden switch back on and drive away hopefully wont happen but its a risk i dont wana take cheers

clifford alarms used to have anti hijack feature that does what you say, bit dearer than a 12v switch though

[Doctor Volt]

What you can do is use a timer relay so that when it is triggered the car can still be driven until that set time is reached and then the fuel or ignition will be cut

[Guesty2015]

steveo3002 said:

clifford alarms used to have anti hijack feature that does what you say, bit dearer than a 12v switch though

Ive seen them been quoted 680 fitted :-0 but the car already has a cat one alarm so id just be paying for this function realy

[JordanTurbo]

Guesty2015 said:

.....it has a cat1 alarm......

A Cat 1 alarm already has dual immobilisation, normally on the ignition and fuel circuits.

Also most Cat 1 alarms have an "anti-hijack" feature which locks the car when driven (normally timed after engine start), meaning you won't get dragged out of the car in the first place. See if you can switch it on?

Chances are your idea with the switch would back fire. What do you think the knife wielding nutter is going to do once the car he just tried to steal doesn't start? Congratulate you on your efforts? I think not.

[Guesty2015]

Doctor Volt said:

What you can do is use a timer relay so that when it is triggered the car can still be driven until that set time is reached and then the fuel or ignition will be cut

Do you mean like a turbo time how it keeps your engine running for so long ?

[Guesty2015]

JordanTurbo said:

A Cat 1 alarm already has dual immobilisation, normally on the ignition and fuel circuits.

Also most Cat 1 alarms have an "anti-hijack" feature which locks the car when driven (normally timed after engine start), meaning you won't get dragged out of the car in the first place.

Chances are your idea with the switch would back fire. What do you think the knife wielding nutter is going to do once the car he just tried to steal doesn't start? Congratulate you on your efforts? I think not.

Thats why i was hoping the car would run for so long and ive been told that the standard alarms are easy bipassed

[Spare tyre]

On an old car I had, I got a spare switch from the breakers and just wired the ignition in line with it

It was a spare fog light switch if I remember right

Looked on and worked well

[JordanTurbo]

Guesty2015 said:

Thats why i was hoping the car would run for so long and ive been told that the standard alarms are easy bipassed

Anyone who is going to bypass a Cat 1 alarm (where the control module and relays are properly mounted/hidden) is going to have no problem spotting a switch that you have to leave accessible enough to flick every time you want to start the car.

[Doctor Volt]

Guesty2015 said:

Do you mean like a turbo time how it keeps your engine running for so long ?

JordanTurbo mentioned about the switch being found easy and I agree

There is a way to get round the switch being found problem

Bearing in mind that when someone steals a car they will not stay with that car for long if it cuts out a minute or so after they have stolen it - The switch can be well hidden under a flap cut out in the carpet under a seat or some place else like that.
The other option is to use a genuine switch that is fitted in the dashboard alongside other genuine switches.
You can even wire up 2 x switches

So going on the switch side of it problem is not so much of a problem with a bit of thought on your part - the job can be done with relays

[Doctor Volt]

Sleep time for me now
I will check back here in the morning

[JordanTurbo]

OP, what car is it? We may be able to give you some more options.

[Claudia Skies]

Another fun thing you can do with your hidden switch involves the horn. You will need a "double pole, double throw" switch. You wire the two sides as follows,

• "Starting" position feed from ignition switch to starter motor relay is interrupted
• "Ignition on" feed from ignition switch is connected directly to the horn.

So unless you reach and flick the switch when you get in the car any attempt to start it will fail and the horn will be sounding constantly. Job done.

[anonymous-user]

Remember that on a modern car, simply removing the power from something will almost certainly result in a raft of error codes and enough warning lights to provide a dam good impression of a rave!


If you're serious, i suggest an cheap pay-as-you go sim card mobile, and an ardunio or similar. If you get jacked, and survive, just send text to car saying "OFF NOW" and it'll shut down. I can't imagine the thieves will stick around with it trying to work out what's wrong (extra points for making fuel guages/range meter show zero so they think it has run out of fuel! ;-)

[anonymous-user]

Switch on the pupm was a great idea in the days of carbs, back in the 70's I parked my MG in a Multi story in london, got back to find it in the middle of the road in the car park and not in a parking spot, it had started on the fuel in the carb run far enough for it to be in an inconvienient place and stopped, they run of and left it rather than stay in the middle of a busy place, today with FI then if they can get around an impobiliser they can get around a hidden switch.