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Disconnect Switch used for Anti Theft

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Disclaimer: I'm not an electrician.

My crazy brain was thinking about using a 175amp disconnect switch on the starter cable between the solenoid and starter as a way to prevent starting the car. I don't want to use it on the battery cable as most do, because I'd have to reset the stereo each time the switch was used. Would a switch on the battery cable interfere or reduce the amps to the starter, or some such thing? Heeeelp Mr Wizard, I don't want to be an electrician...594479bf6bbad_disconnectswitch.jpg.3b2bf8ccf63dc01c7e64f00545277ce8.jpg

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I would think the battery would have to be in the trunk or have a lockable hood, ecspecially if a standard. If they have access to the battery, all they need is a jumper wire to the coil from the battery and a screw driver. 

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If I remember correctly the blue remote wire on the stereo is the constant power feed to keep memory.   You could run that to the battery and then put the switch in the battery cable.  I thought majority if these switches were used to eliminate trickle drain.  

10 hours ago, Caseyrhe said:

I would think the battery would have to be in the trunk or have a lockable hood, ecspecially if a standard. If they have access to the battery, all they need is a jumper wire to the coil from the battery and a screw driver. 

Memory fuzzy on this also, doesn't the key have to be switched on for the solenoid trick work? Yes I think the starter will turn but there won't be fire to the coil with key off? 

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Placing a switch in any line will increase resistance and somewhat disrupt the flow of current. What you suggest is the sledgehammer approach. That's a really really big amp switch, and requires really big wires (cables).

What I have always done is connect a small switch with small gauge wires across the points. If the points don't open and close the coil doesn't work and the engine doesn't fire. If you don't have stock points I would have to see your circuit to tell you how to disable it. The switch only has to handle around 8 amps with a stock coil. Starter motors reportedly pull 60-200 amps, thus the huge switch you suggest. The caveat here is not to leave the key in the run or start position with your "alarm switch" on, as this puts voltage across the coil. It won't kill anything but it heats the coil up. This isn't an inconvenience since the car doesn't start with the switch on anyway, and its natural to turn the key to off. The wires can be easily hidden as can the switch. I remember that in one vehicle I rigged-up the switch to close when the cigarette lighter was pushed in. I don't smoke so I didn't mind that the lighter didn't operate normally. There are lots of creative ways to hide the switch, but I won't tell you mine ;)

 

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6 hours ago, Mach1 Driver said:

What you suggest is the sledgehammer approach. 

You figured me out pretty quickly.

I do have the original points ignition, and an electric fuel pump cutoff switch. The coil/points cutoff switch looks a bunch easier and the best way to go. I know we can't 100% thief proof our cars, but being president of the Department of Redundancy Dept, I gotta try. Thanks to all for the info.

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I know you guys are joking about the gas tank but a fuel cutoff can be an effective anti-theft device. Same as the fuel switch on a motorcycle, you can cut off fuel to the carburetor. A would-be thief steals the car, gets a mile or two down the road, and the carburetor bowls go empty and the car stalls. A stalled classic car in the middle of the road is very conspicuous, especially if it was just reported stolen..

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An electric fuel pump cutoff works best if you have EFI. I had an electric cutoff valve with a standard pump on a carburated car (my first car actually) and that works OK, but as previously stated, the thief can drive a surprising distance on a fuel bowl of gas. I built a home brew alarm that activated a bell, the flashers, and killed the ignition and gas. I built a keypad into the dash to arm and disarm it. This was on a 64 Cheby which sat in a parking lot at work in east LA. At the time they were very popular among Latino's. There were 5 attempts to steal it. One time someone crawled under and took the power steering hoses off !! It had a shaker switch and they still managed somehow. 

As suggested, redundant systems are best. Another method I use locks the auto floor shift in park. Pushing the button on the handle activates a switch that operates a solenoid that pulls the stop out and allows normal shifting. A second switch contact in the kill switch disables the solenoid when open. Of course you need a console to hide all the goodies. If you can deprive them of spark, fuel and lock it in park, they have to tow it away. I intend to add a GPS tracker of some sort. Just because I'm paranoid doesn't mean they aren't out to steal it. My experiences with my first car proved that. The two best places to steal a car are at the shopping mall, and a movie theater. Keep your babies safe.

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The Z-Lok hood lock mechanically locks the hood from opening and kills the coil. I havn't been on their website in a while but they did have a video of installing the unit on a early year Camaro. There are  a number of way to keep the car from being driven off but none of those will stop a tow truck. Depends on how badly the thief wants your car.   Dave R.

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4 hours ago, Dave R. said:

The Z-Lok hood lock mechanically locks the hood from opening and kills the coil. I havn't been on their website in a while but they did have a video of installing the unit on a early year Camaro. There are  a number of way to keep the car from being driven off but none of those will stop a tow truck. Depends on how badly the thief wants your car.   Dave R.

Watched the video on this one before and there was a lot of cringeworthy drilling on the car to put it in, IMO.

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On 6/17/2017 at 9:40 AM, Mach1 Driver said:

Placing a switch in any line will increase resistance and somewhat disrupt the flow of current. What you suggest is the sledgehammer approach. That's a really really big amp switch, and requires really big wires (cables).

What I have always done is connect a small switch with small gauge wires across the points. If the points don't open and close the coil doesn't work and the engine doesn't fire. If you don't have stock points I would have to see your circuit to tell you how to disable it. The switch only has to handle around 8 amps with a stock coil. Starter motors reportedly pull 60-200 amps, thus the huge switch you suggest. The caveat here is not to leave the key in the run or start position with your "alarm switch" on, as this puts voltage across the coil. It won't kill anything but it heats the coil up. This isn't an inconvenience since the car doesn't start with the switch on anyway, and its natural to turn the key to off. The wires can be easily hidden as can the switch. I remember that in one vehicle I rigged-up the switch to close when the cigarette lighter was pushed in. I don't smoke so I didn't mind that the lighter didn't operate normally. There are lots of creative ways to hide the switch, but I won't tell you mine ;)

 

Good stuff...   I have used the "Cigarette Lighter Switch" on a couple of vehicles.   I have also used a small switch attached to where if you pulled the parking brake release out just a little, you could start the car...    I have found over the years that any unique hidden switch keeps unintended people from being able to start a car...    The possibilities are endless...   How about a switch hidden to be closed only when the upper A/C vent is in a certain position???    I LOVE outsmarting the crooks!!!

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If the crooks are as dumb as I am, I could just leave the tranny in reverse. At first I was worried that I wired it wrong, or had a bad ignition switch. But now I go straight to the shifter :(

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So maybe this a dumb idea but when my neutral safety switch went out the car wouldn't start.  What if you wire the kill switch into that circuit?  At least for the AT guys.  Is there a similar switch on the clutch pedal to make sure it is engaged prior to starting?  Thoughts?  Then you wouldn't have the resistance on the way to the distributor. 

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3 hours ago, MN69Grande said:

So maybe this a dumb idea but when my neutral safety switch went out the car wouldn't start.  What if you wire the kill switch into that circuit?  At least for the AT guys.  Is there a similar switch on the clutch pedal to make sure it is engaged prior to starting?  Thoughts?  Then you wouldn't have the resistance on the way to the distributor. 

I like this, if it's feasible. C'mon all you engineers, let's finger this out!

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I wouldn't make it a motion that is necessary to normally start the car- I think most crooks would try the obvious, like clutch or transmission lever.

mwye0627 has some great ideas. A guy on VFM had an interesting method: he put a magnetic reed switch behind the metal dash and activated it with a magnet on the other side in the passenger compartment when he wanted to drive. That ran a relay with a normally closed contact that was put in the circuit as I showed above. You could position it behind the dash anywhere and it would be darn near impossible for a crook to figure out. The only reason I haven't tried that is because I would worry about the metal of the dash getting magnetized and holding the switch closed all the time. I would put it somewhere on plastic like around the steering wheel, or the gauge cluster, or the console.

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On ‎6‎/‎20‎/‎2017 at 2:13 PM, RPM said:

If the crooks are as dumb as I am, I could just leave the tranny in reverse. At first I was worried that I wired it wrong, or had a bad ignition switch. But now I go straight to the shifter :(

I did this not long after I got the car back on the road. Called my old timer car buddy to drive across town to pick us up because the car wouldn't start. When he got there, he shoved it in park and started it right up. Felt like a dumb ass.

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A little bit off topic but the hood latch mechanism from an early '70 Ford pickup is an almost exact copy of the '69/70 Mustang  except that it has a cable release instead of the under the front of the hood manual latch.  It is an exact bolt in to the Mustang's, the only difference is the safety release lever is a little different as I recall. Just pull the truck's latch and remote cable, bolt in the latch and route the cable thru the firewall and mount under the dash next to the parking brake and you have a secure hood. A coil/fuel pump disconnect is a good (and easy) safety backup. I had a coil disconnect switch under my dash of my car but I did something a little different. I purchased a flashing 12v red led light (like they use on alarm systems) and mounted it into my dash. I purchased a Dual Mode Dual Throw (DMDT) switch which allowed me to either switch on the coil when I drove the car and when I wanted to secure it I would toggle the switch which would kill the coil and at the same time turn on the flashing led. I did not have an alarm on the car but the flashing red light would be a deterrent to a possible theft.

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On 6/17/2017 at 8:09 PM, 69RavenConv said:

I know you guys are joking about the gas tank but a fuel cutoff can be an effective anti-theft device. Same as the fuel switch on a motorcycle, you can cut off fuel to the carburetor. A would-be thief steals the car, gets a mile or two down the road, and the carburetor bowls go empty and the car stalls. A stalled classic car in the middle of the road is very conspicuous, especially if it was just reported stolen..

Some number of years ago I saw a security system that allowed the car to be driven a few feet then disabled it. The logic was that in California (I think) a car was only vandalized if a thief broke in and couldn't start the car so the insurance had to pay out less. By actually moving the car, most likely into a traffic lane where it would be very obvious, the car was considered stolen and insurance paid out more.

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