View Full Version : battery kill switches

07-21-2006, 04:13 PM
does a 1500 with a lucas alternator need the alternator wired through the kill switch?

If it does run through the switch, what am I doing exactly? /ubbthreads/images/graemlins/confused.gif /ubbthreads/images/graemlins/square.gif

Of the two regulator leads, I'm isolating the one that's usually always got 12V on it right? not the one that runs through the ignition switch? or do I have that backwards?

Hap Waldrop
07-22-2006, 08:27 PM
I not a expert on kill switches with the use of a alternator, we don't use alternators on the road race Spridgets/MGBs but there are other guys out there racing with alternators and they use a special alternator kill switches. I remember an conversation on the SCCA prod forum about not using these alternator kill switches would not kill the ignition. I read up on this a bit more if it were me.

07-23-2006, 05:06 AM
My Club (EMRA) requires the kill switch but does not test to see if car will die (mine will usualy die anyway, due to special large pully on alternator and slow idle speed).
The vintage club I run with *does* test to see if engine dies, so I just disconnect alternator wires for their events.
Your car will run for hours off just the battery.
By the way, the other Sprite I drive has a driveshaft-driven alternator, so it dies with the kill switch "off" too (doesn't charge under about 40 mph).
Many Spridget guys use a belt that "just" makes it over the water pump and crank pully. Just pry it over...no tension adjustment. You could do this and leave the alternator in place if desired.
Pegasus sells a "diode" kill switch. These are mostly used for rally cars.

07-23-2006, 05:46 PM
Wire you kill switch using the Negative cable NOT the Positive
Get some welding cable from a local shop for this.

Reason being........If the Neg cable gets grounded in a crash.....The only thing that happens is that the circuit is completed.

Use the 4 terminal type kill switch from Longacre ($27.00)

Run your <font color="red">COIL</font> wire through the other part of the switch.

NOT the alternator wire........
Reason being.......you can fry your rectifier by disconnecting that wire while alternator is spinning.

07-23-2006, 06:24 PM
I've got a 4 terminal switch on the way, and wiring the coil through the other two terminals makes sense, also like the idea of the negative cable to prevent a sort. good idea.

07-23-2006, 07:20 PM
Also consider your mounting point for the switch...

SCCA (GCR) says in front of the windshield on the cowl or fender.
(close enough to the windshield to be accessible in the event of a roll over)

OR, Below the center of the rear window.

OR, The roll cage or dash in easy access to someone outside the car. (Welded or bolted only, NO holes in cage for screws)

07-23-2006, 07:35 PM
I'm going to put it in the antenna mount hole on the fender. Should work fine there.

07-23-2006, 08:12 PM
Had mine there........

Finally got tired of un-belting myself to turn the car on. /ubbthreads/images/graemlins/nonod.gif

(Or frantically waving my arms to attract the attention of some nice grid worker) /ubbthreads/images/graemlins/rolleyes.gif

07-23-2006, 09:52 PM

07-24-2006, 06:21 AM
Had mine there........

Finally got tired of un-belting myself to turn the car on. /ubbthreads/images/graemlins/nonod.gif

(Or frantically waving my arms to attract the attention of some nice grid worker) /ubbthreads/images/graemlins/rolleyes.gif

[/ QUOTE ]

Oh brother....been there, done that!

Hap Waldrop
07-24-2006, 08:55 AM
I put my kill switches where I can get to them as well as a worker.

tony barnhill
07-24-2006, 11:12 AM
GREAT! ....&amp; we located my kill switch out on the passenger front sde because there was already a hole there from an`antenna!

07-24-2006, 04:53 PM
When I flipped the Bugeye, the kill switch was mounted on the right side roll hoop. While I was hanging upside down like a fat bat, I couldn't reach it without unstrapping. Well, ain't no way I'm going to do that, so I waited for the corner worker. Let me tell you, when you're buckled in and upside down, it seems like those little bitty SU float bowls hold about 2500 gallons apiece, as they drain.
The first post crash modification was a remote cable to the kill switch, so I could shut it off from the seat.

07-24-2006, 05:31 PM
point taken guys, think it'll end up in arms reach. Now to figure out where that would be....

07-25-2006, 01:06 AM
it seems like those little bitty SU float bowls hold about 2500 gallons apiece, as they drain.

[/ QUOTE ]/ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/eek.gif /ubbthreads/images/graemlins/lol.gif

Ya wanna hear my hood pin story???

Got some advice there also. /ubbthreads/images/graemlins/rolleyes.gif

07-25-2006, 07:57 AM
Just reading all these posts and wondering why not an inertia switch?, am thinking of putting one in, any one have any preferences/thoughts?

07-25-2006, 08:51 AM
In a nasty wreck, the corner workers will be there in seconds.....

If yer taking a lil nap in the car when they get there......They'll take care of everything.

I'm not inclined to install an inertia switch on account of the amount of bouncing around that a race car does during "normal" operation.

I also don't use fuses.

07-25-2006, 08:52 AM
A decent idea, but would not fulfil the requirements of many racing clubs (in the US, at least).
Many newer, ordinary cars have inertia switches on their electric fuel pumps and these are usually left as is if the car is converted to a racer.
One other comment on kill switches: it is useful to keep the unswitched power wire as short as possible...reduces the chance of shorting "before the switch". My battery is just in front of my right-side shock absorber (under the car) and my power wire is in the forward area of the right-rear fender. Easy to reach in a roll-over (well marked) and keeps the unswitched portion of the power wire quite short.
Jeff got me thinking about a remote for this switch...maybe something with a bicycle cable mounted with easy reach (but "Off" only).

07-25-2006, 12:42 PM
do any of the regulations specifically state that it has to be a MECHANICAL switch? If not, something like an ECH ST85 (nice heavy-duty, full-time relay from NAPA, use them all the time on the jeeps) could be used in-line with the ground or positive cable and you could have multiple trigger switches around the vehicle. One could be in the dash, the other on the cowl. You'd have full control of the switch from outside or inside the vehicle.


07-25-2006, 01:21 PM
GCR 17:27 Master Switch

"The master switch shall be installed directly in either battery cable and shall cut all electrical circuits but not an on-board fire system"

Tech guys are like a pack of wolves....

One will ask another one for a second opinion.
A third one will get curious and walk over.
Pretty soon you'll be sponsoring a full blown tech-committee meeting.

(where they<font color="red"> ALL </font>go back over your car and tear it to shreds)

Hap Waldrop
07-26-2006, 06:40 PM
Here, where I mount mine, fire bottle pull handle too.

www.acmespeedshop.com/_images/rearcockpit.jpg (https://www.acmespeedshop.com/_images/rearcockpit.jpg)

07-30-2006, 11:42 AM
Pinto Pic.