Thread: Which wire should I tap???

Ok, so I am going to wire a kill switch up to my AC switch today.. (I mean I'm gonna use it as one) for anti - theft.

Originally I was goning to wire it to the fuel pump, but the ECU would be much more convenient cause of the location (less wires to run across the inside of dash). Not a big deal really, but I'm just wondering if anyone has any good advice here. This is part of the ECU pinout with the most important stuff on it. I was debating wiring it to the power transistor, but now a friend pointed out if someone tries to start it then it'll still get tons of fuel in the engine which would be stupid. Fuel pump still might be best? What do you think?

i dont even see the AC switch on that wiring diagram, pull the switch out and see how many wires are on it, dependin on how many wires you can find the two and check for continuity, open and closed to figure out what wires to use, then just ground one side, and run the other wire to the clutch switch in a series, then you will have two switches to start the car

i did this

Clutch switch is a good plan, never crossed my mind lol. The AC switch is on that diagram, but lower down. My original intention was to simply clip all the AC switch wires since I don't have AC, and just use it as a normal switch.

On a side note, having two switches won't matter if they are both triggered by the same switch

Ok looks like I am just gonna use fuel pump.. pretty straightforward and I can tap the wire under the carpet instead of having to deal with the mess of fuse box wiring and ECU harness. For reference, here's the fuel pump diagram and the wire color codes too.

Ok just a final note, I went ahead and wired the fuel pump wire to the AC switch (though I am slightly nervous still as I am not 100% sure it can handle that much current) but as of now it seems to be working fine.

A better option would have been to use the fuel pump relay wire instead as it carries much less current. (More of a PITA to track down, however).

well that inst true, the will both have to be triggered to work, if you have your clutch switch wired in with another switch, im not so good at explainin things but im gonna do my best, factory uses a wire out of the steering wheel for a ground for the horn the ground activates the relay for the horn to go, like i said you will have to wire it in series, so wire out of the steering wheel will go to the ground side of your clutch switch, so you push the horn buttom you have ground, instead of a chassis ground you have ground by switch, then you push the clutch in and it closes that switch, so then you have ground to activate the starter relay witch sends signal to turn the motor over

so two switches will have to be activated to start the car, you push the clutch nothing, then you push the horn buttom and you have ground

so with the horn button not pushed and the clutch not pushed you have two open switches, with only one pushed you have one closed switch and one open switch so you get no grounding for the starter relay, but once you push both you will get a signal for the realy to activate

if this doesnt make sense i can make a figure after work

I like the horn to start ,good idea,but then it honks every time you go to start it?

No haha it makes perfect sense, I just thought before that you meant to ground the clutch sensor through the same switch as the fuel pump connection so as to activate both at once when pushing the switch .

The problem with the horn is that you can only use it for something like a clutch as it's not a toggle switch. But you can start the car without the clutch sensor by rolling it, so it isn't foolproof as an anti theft method (hence the reason I went with the fuel cutoff instead).

Fuel cutoff is foolproof until someone actually realizes there's a switch, unlike a clutch cut which can be got around by a roll start (which isn't too hard outside of a parellel parking spot).

Now I just have to hope the smaller guage of the AC switch doesn't mean I'm going to lose fuel pressure or melt the switch!!! Time will tell. For future reference, anyone planning on a pump cutoff, you should put your switch on the pump relay wire isntead of the pump power wire, so as to avoid worrying about this . It's more of a PITA but I'd do it that way if I did it again I think..

ah i gotcha on this, so this fools can basically push start the car, i never thought about that

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