battery cut off switch

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bluefish

mopar dave
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anyone know the proper way to wire a battery cut off switch? i'd like to wire my fuel pump and ignition box to the starter side of the switch, but not sure if this will work. to me, when the switch is turned to off this would break the circuit to the pump,box and battery and should kill the motor. will this work wired this way?
 
This might not be what you are looking for but wouldn't the fuel pump and ignition box be wired in with your fuse panel?

switchWiringDPST.jpg
 
hi bluefish
very easy. first you will need a 4 post switch
then battery positive cable to one of the large posts.
cable going to starter on the second large post.
a jumper wire roughly 10 gauge ( 3 inches long)from one small post to the large post of battery cable large post.
and lastly the second small post on the switch you run a wire from it to the battery post of your alternator. you will disconnect the current wire going to this post and tape it off.it is a hot wire and will not need it. i have founf that this will shut of the car when it is running. no juice at all. the only down fall on the hook up is your amp gauge will not work correctly. but since i run a volt gauge it didn't matter to me.
hope this helps
terry
 
Have you looked into a battery cut off switch kit?
 
thanks guys. i did'nt know there was a kit available. whats included in it? i currently have my fuel pump and ignition box main power hooked directly to the + post of the battery in the trunk and thought i might be able to wire these to the cut off switch somehow.
 
ok, i like the second diagram. there's no extra relays needed, but the + wire from the alternator in hooked the battery + and has power weather the switch is open or closed. i don't understand how the power could be cut if the alt. wire always has power. would'nt the engine continue to run with the switch open?
 
ok, i like the second diagram. there's no extra relays needed, but the + wire from the alternator in hooked the battery + and has power weather the switch is open or closed. i don't understand how the power could be cut if the alt. wire always has power. would'nt the engine continue to run with the switch open?

No, because the alternator is hooked in up stream from the cut off switch. It's not hooked to the starter relay lug in the engine compartment.

I actually like the extra relays in the trunk because it cuts ALL hot wire to the front. Using the ford starter and a continuous duty relay for the alternator, once the cutoff switch is thrown there are no hots beyond the cutoff and relays.
 
ok, if i run a wire from the alt. positive post to the cut off switch, what do i do with the + wire currently on the alt. post ? if i remember right this wire goes to the ammeter and then to the starter relay.
 
ok, if i run a wire from the alt. positive post to the cut off switch, what do i do with the + wire currently on the alt. post ? if i remember right this wire goes to the ammeter and then to the starter relay.

Remove it from the system entirely, both ends. If you leave it hooked up in stock form, the cutoff switch will be ineffective.
 
i currently have a voltmeter in the system. i found another way to wire the switch which may be less work/time. if i run my field wire from alt. to switch and from the other side of the switch back up to the voltage regular to complete the circuit. ya think this will work with a 4 post switch?
 
Could you guys post some pictures of a battery cut off switch that is remote. I'm trying to get some ideas to make it pro-steet compliant but, not have a big switch hanging under the rear of the car. Here is my battery box and I would like to keep everything in the trunk if I can. Much appreciated....:prayer:
 

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If you plan on taking your car to the track you need a battery cut off switch on the rear of your car on the out side. Not in the trunk. You can install it so it's not hanging below the car.
 

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Thanks, I know the control for the battery cut off has to be on the outside of the car. That is where it wil go on my car but, I want to have the switch inside the car...using something like a push - pull rod or tele-flex cable and a well marked "T" handle, Maybe coming through a bumper bolt or something like that.
Cheers
 
You need to read the rules. The cut off MUST either be "twist to the left" for off or PUSH for off, NOT PULL It MUST be in the battery HOT lead, and it MUST kill the engine and fuel pumps. If you rig it to kill ALL power that much the better.

For unexplainable reasons you can download the much guarded NHRA rules from the Bremerton Raceway site fer free:

www.bremertonraceway.com/2011 NHRA Rulebook.pdf

IT IS IMPORTANT to realize that if all you do is cut the battery lead, the alternator will continue to run the engine. THIS DOES NOT satisfy the rules.

One way to do this is to buy a Cole Hearse 4 terminal switch, known as a "2 pole" or "double pole" switch.

It has 2 large heavy current terminals and 2 small "control" terminals.

MasterDisconnectDPST1.jpg


Hook your switch in the hot battery lead using the 2 large terminals, ground one of the small terminals, and run an extra no16 or 14 wire up front, hooked to the remaining small terminal of the battery switch.

Buy yourself a good quality "Bosch" relay with a mounting tab so you can mount it somewhere.

bosch_relay02.jpg




Run "switched ignition" to one of the coil leads of the relay (85), and run your disconnect switch wire to the other coil connection (86).

Run a fused (10A plenty) hot lead to one contact (30), and hook the other contact to the field of your alternator IF YOU ARE USING a 70/ later alternator/ regulator setup (87). (NOT 87A)

RelayWiringGuide.jpg


If not, you can run the second contact to the IGN terminal of your regulator (69/ earlier) OR even use that contact to supply the ignition system. This works well if you are using a "one wire" alternator, but if you use the relay to power the ignition, you probably want heavier wire and a larger fuse

or if you want overkill, use a "constant duty" solenoid

41FzfHIEG6L._SL500_AA300_.jpg


IN OTHER WORDS the disconnect breaks BOTH the battery hot lead, AND it breaks the IGN supply to the alternator to cut the alternator

The point is, when someone operates the disconnect, it WILL kill the engine, pump, everything.
 
Gotchya! I was going to hook up a bell crank to shut off my fuel valve as well. I did not know it had to be "Push for off". Good to know. I'm also going to install a "lock out" for off track. That way no smart *** can shut off my power or fuel on the street.
 
I believe the rulebook states (General Regulations, page 32) that the battery box must be sealed and has to be vented outside the body, probably reduced risk of hydrogen gas. You can confirm by reading the rule book.
 
I believe the rulebook states (General Regulations, page 32) that the battery box must be sealed and has to be vented outside the body, probably reduced risk of hydrogen gas. You can confirm by reading the rule book.


Yup, and also, I believe unless the battery is completely enclosed and vented in a ??metal?? box, you must have a firewall between the trunk/ interior of the car.

Yup read the rules.
 
Fellows, please read, see what you think, and comment on this.

I am looking at the 1970 Plymouth service manual for the 340. Think first in terms of the stock setup. From the positive side of the battery you have heavy wire going to the starter and a lighter wire going to the starting relay (B terminal). The starting relay has terminals for (B)attery, (S)tarter (I)gnition and (G)round. The I wire feed goes to the ignition switch via the bulkhead. The control wire from the S terminal goes to the starter solenoid. And the B terminal has a wire feed going to the fusible link and from there to the bulkhead and from there the ammeter, number 1 link, then branches out into headlight switch, horn, etc, another separate feed back through the bulkhead and to the B terminal of the alternator.

That said then, can’t you then just run from the positive terminal of the battery to a two terminal master cutoff switch and have wires as previously described run to the starter and to the starter relay from cutoff switch terminal farthest away from the battery? On that same terminal attach everything else (fuel pump with link, etc). Won’t that kill power to everything? Just make sure the feed wire from the battery to the master cutoff switch is heavy gage as well as the wire cranking the starter. The control wires can be the same gage as stock. The master cutoff switches are sold on Ebay Motors all the time for about 16 bucks.
 
sealed/gel cell batteries do not require venting.

There are a bunch of ways to do a remote cut off switch, some better than others.

4642211-MVC-022S.jpg

4643103-MVC-024S.jpg

4809942-MVC-025S.jpg
 
Tom Oliver;1645816 That said then said:
No, Once the alternator starts charging, it will keep the engine running even though the battery is disconnected.

Some guys like to run one huge wire from the battery up front with the disconnect inline, and a second, say, no6 or no4 from the alternator direct to the battery

This scheme would allow the engine to die, but then you still have a big wire hot, from the battery clear up to the alternator.

This is the same scenario that I try to get guys "not" to do, the alleged wives tale of "testing the alternator." The premise is, you remove the battery cable, and if the engine keeps running, the alternator is OK.

That is what happens if all you do is break the battery connection.
 
sealed/gel cell batteries do not require venting.

There are a bunch of ways to do a remote cut off switch, some better than others.

4642211-MVC-022S.jpg

4643103-MVC-024S.jpg

4809942-MVC-025S.jpg

Thank you for so much info. This "T" handle that remotly disconects the battery is just what I was thinking about. My battery box seals and vents outboard even though I will be using a OPTIMA. I will be sealing off the truck from the flight deck as well just incase. FAR 25...lol. Thank you for the rule book referance as well. Great stuff everyone. THANK YOU! :prayer:
 
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