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Old 06-13-2009, 08:41 PM
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battery in trunk and kill switch question

Got a project with no motor / trans in it . Car has battery box in trunk and a cut off switch in the back - The ford solenoid is mounted up front on the firewall .
Now , at back of car off the cut of switch - one term. is going to the battery box and from battery box the cable goes up the passenger side of car to the solenoid up front on firewall . Off the other side of the cutoff switch the cable is going up the drivers side thru the firewall and goes about 2 1/2 to 3 foot past the firewall - This would go to the alternator post correct ? ( this wire was not marked and the person i got it from said the car didn't have a alternator hooked up as it was a track car )

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Old 06-13-2009, 09:13 PM
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No it does not go to the alternator. A cutoff switch needs to be as close to the battery as possible. If it's a single pole cutoff switch one wire from one side of the switch goes to the positive battery connection. The other wire from the other side of the cutoff switch goes to one side of the Ford starter solenoid. Another wire from the other side of the Ford solenoid goes to the large lug on your starter. Were talking battery size cables here, not smaller wires. If you have a GM starter it must have a jumper installed on it to work with the Ford solenoid.

On the off chance that I misunderstood what your asking: If there is another wire off the other side of the cutoff switch that is a smaller wire then it will go to either a fuse panel (power) or to a junction lug on the firewall. If you choose to go with a firewall juntion lug you will have one wire from it going to power your fuse panel and another wire from it going to your alternator big lug.

Vince
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Old 06-13-2009, 09:33 PM
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I'm a little confused by your description, because it doesn't sound like the cutoff switch is wired to cut off power to the engine compartment.

Typical wiring would be:
- The battery cable will run from the positive terminal of the battery to the cutoff switch at the rear of the car.
- On the other terminal of the cutoff switch, the large cable will run from the cutoff switch up to the engine compartment. If the cutoff switch is off, there will be no power running up to the engine compartment.
- At the engine compartment the large battery cable will connect to one side of the Ford solenoid. They might have also used that terminal of the solenoid to power the fuse box, lights, etc., since it will have continuous power as long as the cutoff switch is turned on.
- The other side of the Ford solenoid will have a large cable running down to the starter. When the solenoid is activated by the wire connected to the ignition switch, it will make the starter turn over.

There may also be a slightly smaller gauge negative cable that runs from the battery up to the engine. This method will usually be a little more reliable than using the vehicle frame to ground the negative cable for a trunk-mounted battery.

Bruce
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Old 06-13-2009, 09:43 PM
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The battery kill switch should be hooked to the battery ground cable, not the positive cable.

I like to interupt the ground wire to a relay to keep a engine from starting, heck, I have to instal a kill switch on a brand new Toyota Pirus real soon. This will be fun!

It helps to know what you are working on also.
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Old 06-13-2009, 10:02 PM
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Quote:
Originally Posted by carsavvycook
The battery kill switch should be hooked to the battery ground cable, not the positive cable.

If this car is going to see the drag strip again, rules require the switch to interrupt the POSITIVE cable, and will not be legal if hooked up in the ground cable.

Does this cut-off switch have just two battery cable posts?? Or does it also have two smaller (10 ga) posts?? If it has the smaller ones too they are for the alternator main lug only so that the alternator won't keep powering the car even with the switch shut off. The drag techs check to see if shutting off the switch kills a running engine.
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Old 06-13-2009, 10:11 PM
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Thanks guys , iam not sure what the other owners had going with the wires . When i got the car it had no battery just the battery box and the wires the way in this paint pic ( the ends are right at the battery box ). I am just lost on what and why the wire on the driver side is run there ( the wires going up both sides are welding cable and thick )
The wires under the hood except lights , horn , wipers are cut off ( like the hei one is cut and alt wires too ) Off the solenoid there is a wire going to an arc prostock box that does ing and nitrous controls , lights , fuel pumps ect.

only 2 studs on the cut off switch



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Old 06-13-2009, 10:38 PM
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I would say that the cable on the drivers side is a dedicated ground from motor to battery and shouldn't be hooked to the switch if this is to be NHRA/IHRA track legal. They have it wired like Carsavvy said and isn't legal that way. The switch should be in the pass side hot cable going to the solenoid.

I realize what Carsavvy has said, and have gone around with track tech about this as interrupting the ground makes more sense, but then again nobody said the NHRA has ever had much sense to a few of their rules.

Don't get me started on their "every 2 years expiration" of 5-point seat belts
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Old 06-13-2009, 11:48 PM
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If both of the battery ground wires(battery to engine, and battery to frame) are killed, it will not run. It takes a less amperage rated switch to accomplish this.

I have argued about this with some tech's, and won all of them over to this.

This does not include the ignition kill lanyards worn by the driver, encase they are thrown out though.

Last edited by carsavvycook; 06-14-2009 at 12:29 AM. Reason: Wrong Word used
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Old 06-14-2009, 07:16 AM
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If one person says it's light outside another will say that it's dark. Our differences is what makes us great.

Vince
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Old 06-14-2009, 06:12 PM
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NHRA Rulebook 09

Section 19 - General Regulations

Para. 8.4 Master Cutoff

Says it has to be on the positive cable and the word positive is in bold. There may be good reasons to do otherwise, but if you are running at an NHRA track, you may end up not running.
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Old 06-14-2009, 06:39 PM
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We still don't know if this was, or is, a drag car. It could be a 'left turn only' car also. So whose regulations do we go by?
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