260zjade Posted January 7, 2007 Share Posted January 7, 2007 ok...so my 1974 260Z got stolen the other night...and the cops returned it to me hours later...unscathed...i know...lucky...but anyway...i wanted to put a kill switch in it to deter theft and stuff like that...i planned on doing it in the cigarette lighter...i was gonna run a hot lead from the battery to the lighter...and then a ground out to the starter relay...push in lighter...start car...lighter pops out and reactivates the "kill switch"...i hooked it all up...turned on the car...and then tried to turn it over...when i did...the whole wire...all the way back to the battery...fried...so mch smoke i thought there was gonna be a fire...and the car didnt start either... so there is the explanation...now whats the cause... checked to make sure the lighter was 12volt...i have a 12volt inverter that works in it all the time... checked to make sure the hot lead idea was a good one...the power that passes from the battery to the solenoid goes straight through the starter relay...so there was no error there... the only thing left that i can think of is that 1) i used to small a wire... or 2) the lighter cant displace enough electricity to keep up with the amps flowing through the wire... now i know next to nothign about electricity...but i thought when the lighter was engaged...all it was doing was linking the wires connected to it...creating a complete circuit...and mimicing the setup that was there before i tampered with it... anyone know why this would happen...or how i can fix the problem? A friend suggested that the lighter wasnt 12 volt and that i would need a resistor on the battery side of the lighter...and a capacitor on the relay side...to make the circuit work...so i am thouroughly confused... anyone help? Quote Link to comment Share on other sites More sharing options...
z-hag Posted January 7, 2007 Share Posted January 7, 2007 my fuel cut-off switch in my slikky was under th e dash, to the left of the steering column.,.,.. Quote Link to comment Share on other sites More sharing options...
260zjade Posted January 7, 2007 Author Share Posted January 7, 2007 i thought about fuel cut-off...and a switch on the ignition switch...but when i thought about installing the kill switch...i wanted something that would reset itself after i started the car...a lighter...a push button switch...something that i would hold while i started...and then release afterward...i wont remember to switch a manual switch back when i shut the car off... and as i was thnking about that...i realized that ignition switch...and fuel cutoff...would both shut off the car if i used the lighter or a push button because it would only stay active while i turned on the car...the only mechanism i can think of that can allow me to do what i want...and be very hard to hot wire...its a set up using the starter relay... i guess what i really meant to ask was can this be done? Quote Link to comment Share on other sites More sharing options...
SHADY280 Posted January 7, 2007 Share Posted January 7, 2007 the problem was prolly to small of a wire, plus no fuse. the cigarette lighter can be used, first get a spare lighter, solder it up, then make it so that when pushed in, it completes the circuit, when pulled out, no circuit. its a neat way to get it to work, but it is just a big resistor and cannot really transfer load without creating heat. Quote Link to comment Share on other sites More sharing options...
260zjade Posted January 7, 2007 Author Share Posted January 7, 2007 ok...so what i need to do then is use a bigger wire...but if the lighter is a big resistor...is it going to transfer any power to the relay to get it to switch over and engage the starter motor? and it does generate heat...but i dont think its supposed to fry the whole wire...will a bigger wire solve the problem...or is the high resistance the problem? Quote Link to comment Share on other sites More sharing options...
SHADY280 Posted January 7, 2007 Share Posted January 7, 2007 kinda both things are the problem, to get it to transfer power, thats what the soldering is for, it gets rid of the resistor and transfers energy. what size wire did you use? if its for a relay, then 18 gu. is fine, if its anything else size it correctly for the amperage thats is going to flow down it. you prolly had 18 gu, just the resistor in the lighter fried it cause they use 20 amps or so. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted January 7, 2007 Share Posted January 7, 2007 The heating element in the cigarette lighter is a resistive coil. I believe the voltage drops across the coil thereby increasing current through the wire. So the wire could overheat... depending on power demand. EDIT: You could probably make it work but I don't know enough to help. Quote Link to comment Share on other sites More sharing options...
260zjade Posted January 8, 2007 Author Share Posted January 8, 2007 ok now were getting somewhere...so if i decided to sauder the lighter...exactly what...or how would i do that to lower the resistance? Quote Link to comment Share on other sites More sharing options...
260zjade Posted January 8, 2007 Author Share Posted January 8, 2007 sunmaster...im sorry...i dton understand...if i connect the ground to the slot where the 12v hot lead plugs in...then what do i connect to the relay?... please bear with me guys...im tryin!! Quote Link to comment Share on other sites More sharing options...
SUNMASTER Posted January 8, 2007 Share Posted January 8, 2007 sorry it is 3:00 AM in the morning i reread Your post . The way i see it when You start the car You turn the ignition switch..... current flows from the ignition to the starter relay's coil. that should be the 12v positive side . The other side of the relay coil goes straight to negative (earth) As soon as You turn the key the relay pulls in and the contacts inside the relay close to let the current flow from Your battery 12v positive side to Your solenoid. Now You have to remove the negative wire from the relay coil and run a new wire from the starter relay coil's negative side to the lighter and connect it in the place of the original wire that was supplying the lighter with 12volt positive to complete the cicuit. i would also sujest bridging out the resistance coil in the lighter........but this will mean that You have to push in the lighter to start the car and remember to pull it when you want to isolate that circuit I hope this will help ......please ignore the previous post of me Quote Link to comment Share on other sites More sharing options...
260zjade Posted January 8, 2007 Author Share Posted January 8, 2007 thank you very much! i think i got it working...as long as i can keep the two seperate components inside the lighter (pos and neg) from touching...then it works as a switch...the lighter doesnt appear to be heating up though...i changed the hot wire from gauge 18...which fried...to guage 12...which didnt...is the large guage lowering the lighter resistance and therefore keeping it from heating?...doesnt matter that much... thank you all...i just need to figure what guage to use and what size fuse...you all have been very helpful!! Quote Link to comment Share on other sites More sharing options...
SUNMASTER Posted January 8, 2007 Share Posted January 8, 2007 Glad you came right Quote Link to comment Share on other sites More sharing options...
260zjade Posted January 8, 2007 Author Share Posted January 8, 2007 definetly! Quote Link to comment Share on other sites More sharing options...
twoeightythreez Posted January 8, 2007 Share Posted January 8, 2007 Good Idea, but I don't want to deter you but it won't help much unless the thief knows nothing about cars (all you have to do on a Z is pop the hood & you can reach in there with a small key or screwdriver to crank the engine, the power to the starter itself is right next to the solenoid wire ) It'll be a cool little trick to impress your friends with though. I hope you fused that 12ga wire, unless you like melting stuff in case of a short, a 12ga wire could actually set your car on fire before it parts from the heat. Sunmaster, you're actually reversed, in a DC circuit current (electron flow) flows from negative to positive. In a negative ground automotive circuit that makes sense since the body of the car acts as a giant bus bar for power distribution. The actual current flow for the starter solenoid is actually out the neg terminal, through the engine block, through the solenoid windings, then out the wire, through the ign sw turned to "start", into the wire harness, through the fuse panel and then the electrons complete thier journey by re-entering the battery's postitive side. The magnetic flux created by the electrons flowing through the solenoid pulls the plunger back which completes the circuit to the starter windings, as well as pulls a lever which forces the drive gear against the ring gear. Since the lighter is grounding when you push it in it's creating a short, which is melting the wire. Doesn't the lighter already have a power supply? Couldn't you just tap off the body of the lighter (neg. side) to a standard fog-light relay's relay coil? This way you're not passing tons of amps thru something not designed for it. Plus, the resistance of the relay coil is high so you won't have a short, and the lighter should still work. (since you'll be wiring the relay in parallel instead of series) The other terminals could just be spliced into your existing ignition wire so it won't pass current to your starter solenoid. Here's a general idea of the relay connections 4 terminals on a relay 86, 87, 30, 85. Usually the relay coil is 86 and 87 usually the contacts are 85 and 30 have your wire to the solenoid on terminal 30 ignition switch on terminal 85 terminal 86 to - side of lighter (keep existing ground though) terminal 87 to a separate ground This way (i think) the ligher will still work as it should (relay field coil takes only 300mA or so) and the switching function will switch the relay. This way when u push lighter in you'll see 12v on the relay coil which will close the contacts and allow you to start the car with the key. The lighter since it will still have it's own power source and ground will heat up, pop out and disable your starter. This is basically how flashing sidemarkers work, one side of the bulb is wired to ground side of turn signal bulb. When lights are off the turn signal grounds thru the sidemarker light, which makes them both light. When lights are on they flash out of sync since 12v is present on both sides of the sidemarker bulb when turn signal lamp is on, since no diff of potential no current flows and bulb goes out. This is why you can't have power on lighter from batt and also have power from key, no current will flow. Ok enough blabbering for me. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted January 8, 2007 Share Posted January 8, 2007 I'm not sure I understand what you mean by "solder the lighter". If you mean fill the heating coil with solder... please DON'T do that. You'll create a direct short and REALLY catch your car on fire. The only way I would know how to make your idea work is to convert the lighter to a switch. That would take some custom work but it could be done. I'm sure there are other ways but I'm not savvy enough to know how. ok now were getting somewhere...so if i decided to sauder the lighter...exactly what...or how would i do that to lower the resistance? Quote Link to comment Share on other sites More sharing options...
SHADY280 Posted January 8, 2007 Share Posted January 8, 2007 your soldering the side you would normally light the cigarette with, therefore creating a flow through the unit. dont hook a ground up to the lighter center post, it now becomes the "out" flow to the relay, and the stock "in" wire is the power that does the relay switching. i wish i could give ya a diagram, but im not that savy. when the lighter is pushed in, it connects the circuit with the little spring prong in the bottom so ya can start your car, pull it and no power. it probably be best to stop power to the coil and starter, then the crook has 2 things to look for. and its easy to hide in the engine bay harness and make look stock. make sure to use fuses, and solder all connections and heat shrink. dont go cheap or you could poss. get stranded somewhere. Quote Link to comment Share on other sites More sharing options...
Guest TeamNissan Posted January 8, 2007 Share Posted January 8, 2007 Good Idea, but I don't want to deter you but it won't help much unless the thief knows nothing about cars (all you have to do on a Z is pop the hood & you can reach in there with a small key or screwdriver to crank the engine, the power to the starter itself is right next to the solenoid wire )It'll be a cool little trick to impress your friends with though. I hope you fused that 12ga wire, unless you like melting stuff in case of a short, a 12ga wire could actually set your car on fire before it parts from the heat. Sunmaster, you're actually reversed, in a DC circuit current (electron flow) flows from negative to positive. In a negative ground automotive circuit that makes sense since the body of the car acts as a giant bus bar for power distribution. The actual current flow for the starter solenoid is actually out the neg terminal, through the engine block, through the solenoid windings, then out the wire, through the ign sw turned to "start", into the wire harness, through the fuse panel and then the electrons complete thier journey by re-entering the battery's postitive side. The magnetic flux created by the electrons flowing through the solenoid pulls the plunger back which completes the circuit to the starter windings, as well as pulls a lever which forces the drive gear against the ring gear. Since the lighter is grounding when you push it in it's creating a short, which is melting the wire. Doesn't the lighter already have a power supply? Couldn't you just tap off the body of the lighter (neg. side) to a standard fog-light relay's relay coil? This way you're not passing tons of amps thru something not designed for it. Plus, the resistance of the relay coil is high so you won't have a short, and the lighter should still work. (since you'll be wiring the relay in parallel instead of series) The other terminals could just be spliced into your existing ignition wire so it won't pass current to your starter solenoid. Here's a general idea of the relay connections 4 terminals on a relay 86, 87, 30, 85. Usually the relay coil is 86 and 87 usually the contacts are 85 and 30 have your wire to the solenoid on terminal 30 ignition switch on terminal 85 terminal 86 to - side of lighter (keep existing ground though) terminal 87 to a separate ground This way (i think) the ligher will still work as it should (relay field coil takes only 300mA or so) and the switching function will switch the relay. This way when u push lighter in you'll see 12v on the relay coil which will close the contacts and allow you to start the car with the key. The lighter since it will still have it's own power source and ground will heat up, pop out and disable your starter. This is basically how flashing sidemarkers work, one side of the bulb is wired to ground side of turn signal bulb. When lights are off the turn signal grounds thru the sidemarker light, which makes them both light. When lights are on they flash out of sync since 12v is present on both sides of the sidemarker bulb when turn signal lamp is on, since no diff of potential no current flows and bulb goes out. This is why you can't have power on lighter from batt and also have power from key, no current will flow. Ok enough blabbering for me. This is the correct response lol. Quote Link to comment Share on other sites More sharing options...
SUNMASTER Posted January 8, 2007 Share Posted January 8, 2007 Sunmaster, you're actually reversed, in a DC circuit current (electron flow) flows from negative to positive. In a negative ground automotive circuit that makes sense since the body of the car acts as a giant bus bar for power distribution Yes thank You for the correction , but there is nothing wrong with the circuit i described . It would not matter whether it flows from positive to negative or the other way around. Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted January 8, 2007 Share Posted January 8, 2007 you want to get REALLY SNEAKY......install a burgalar alarm contacting contolling the electric feed to the ignition (not the starter)in your center console that only closes when your seated with a magnet on your belt,(he wears a magnetic clip for his keychain on his hip) my buddy did that on his 1974 corvette and even with the key it won,t fire up, yeah it still will crank but not run, unless hes seated in the drivers seat. he says its a P.I.T.A. when he forgets or moves around alot, but it sure works Quote Link to comment Share on other sites More sharing options...
savageskaterkid Posted January 9, 2007 Share Posted January 9, 2007 I think they're called magnetic switches. Where as long as you have power running through the switch it is a closed circuit. But once you cut power the circuit is open and you must actually push in the swith for it to restart. This is what I plan to do, with all my switches, because I have a bad tendency to forget to turn things off. Quote Link to comment Share on other sites More sharing options...
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