Does it matter which wire you install a battery disconnect on? I put mine on the + wire, then started thinking about it, then read the directions, and it said on the - side. Does it matter? Toqwik
I have mine on the negative side.........when the ground is GONE.....nothing wants to work....... I read the instructions too........so thats WHY......
I think we had a thread on this a while ago. I've run mine on the negative terminal for 25 years. I think the opinions were for it to be on the positive terminal. There are switches that have a pair of large terminals for the battery cable and a pair for the charge wire from the alternator. This double switch is used to prevent run on from the alternator powering the car once the battery cable is disconnected. I would use one of these double switches, on the positive side, if I were putting one in now.
Mine works like a KILL switch. When the car is running and you hit the switch, everything shuts down imediatly. I put a diode in line from the alternator to keep it from back charging and it works like a one way switch so that the car would indeed DIE. without one the car will still run because it is running off the alt. or gen. Hope that made sence. I found that NAPA has the diodes for around 14 bucks where as the kit diode sells for about 50, and it's basically the same as the NAPA piece.
NHRA requires it to be on the positive side for racecars. If you're just planning on using it as theft prevention/storage it won't matter, and a two post, for the main cable, will work. If it's for racing, it must be on the rearmost portion of the car, and clearly marked for the OFF position, and the four post is recommended if you have an alternator. Mutt
The important thing is for the disconnect to be on the ground terminal, right? An old 6-volt, positive ground should have it on the positive terminal, no? Why would the NHRA mandate a positive ground application?
[ QUOTE ] The important thing is for the disconnect to be on the ground terminal, right? An old 6-volt, positive ground should have it on the positive terminal, no? Why would the NHRA mandate a positive ground application? [/ QUOTE ] It might be a case of NHRA not making a note of the difference between 6 volt pos. ground and 12 volt neg. ground. I have run battery cutoff switches either way. Usually in the pos. cable on 12 volt neg. ground systems. If the cutoff switch has the "field interupt" terminals (the two small ones) it won't make much difference which polarity is "cutoff."
I'd vote for (and my car is set up with) it on the negative side. I use this logic... if I have the + side disconnected and I drop a wrench on the + post, I'm still gonna get a hell of a spark. if it's on the - side, I can drop the wrench on either side with no sparking... unless it hits both posts!
NHRA does mandate it for the POS. side. I had to diode mine, because they did'nt make the 4 post switch at the time, and yes mine is NHRA approved. Mounted at the rear with hand painted on/off on the pass side. Must be that way in case of rollovers, stuck throtles ect...
[ QUOTE ] NHRA does mandate it for the POS. side. I had to diode mine, because they did'nt make the 4 post switch at the time, and yes mine is NHRA approved. Mounted at the rear with hand painted on/off on the pass side. Must be that way in case of rollovers, stuck throtles ect... [/ QUOTE ] The SCTA (Southern California Timing Association) also requires an "emergency electrical cutoff switch" for the same reasons. In our B/STR I installed the cutoff in the pos. lead. It is 12 volt negative ground electrical system. Because we don't run a generator or alternator we don't have to be concerned about "back feed." It really doesn't matter which (pos. or neg.) wire is interupted; the whole idea is to "kill" the electrical system. For those that have clocks or radios (memory settings) or electric door locks; interupting the GROUND of your electrical system eliminates any of these devices from operating. Interupting the HOT side allows for a "bypass" connection to keep the locks, clocks and memory settings to continue to operate; even though the rest of the electrical system is "dead."
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