• VKZ24
  • VKZ24
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  • From: Wilson, NC
  • Registered: 2009-05-20
  • Posts: 1,840

Topic: Let the flames begin (kill switch question)

I *really* hated to post and ask this question, but I’ll take the flames over buying another alternator.

First off, yes, our kill switch DOES work as currently wired.  We have run the car in 5 races thus far.  However right before a race earlier this year our alternator up and quit.  Since it was almost new when we bought the car I thought it was odd, but whatever shit breaks right?  Recently it got me thinking that maybe it was due to the voltage spike due to our kill switch being wired incorrectly?  Take a look at the diagram below which show the way ours is currently wired.  The DPST style switch is from Longacre Racing.  Does our current setup lend itself to the infamous spike that can fry the diodes in the alternator?

http://i164.photobucket.com/albums/u9/VKZ24/Prelude/KillSwitchSchematic.jpg

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  • BoB
  • BoB
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  • From: Elmhurst, IL
  • Registered: 2009-05-01
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Re: Let the flames begin (kill switch question)

here is the diagram from our kill switch.

http://www.pegasusautoracing.com/pdfs/4 … ctions.pdf

It has a resistor going to ground so that current won't feed back into the alternator and fry it.  Not saying this is what happened to your but its possible.

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3 Reply by DaveH (edited by DaveH 2010-11-22 01:40 PM)

  • DaveH
  • DaveH
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  • From: Delaware
  • Registered: 2009-05-11
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Re: Let the flames begin (kill switch question)

http://farm6.static.flickr.com/5128/5199075803_461408d29c_b.jpg

Do this.  Although I hope the big line is going to the starter, not the fuse block.

I also forgot a fusible link.  You should have a 100A or 150A fusible link between the battery and the alternator.  Most cars have these in the wiring harness.

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  • From: Land Of Subarus, Colorado
  • Registered: 2009-04-30
  • Posts: 9,416

Re: Let the flames begin (kill switch question)

A few teams use a 3-pole (TPST?) kill switch, using one of the circuits to kill the alternator field coil. According to the super-anal freakos who use this setup, you'll spare the diodes if you kill the field at the same moment you kill the output. I suppose you could also accomplish the same thing with a DPST and a relay controlling the field.

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  • From: Charleston, SC
  • Registered: 2009-08-08
  • Posts: 466

Re: Let the flames begin (kill switch question)

+1 Phil!!!!!!

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  • Registered: 2009-09-22
  • Posts: 367

Re: Let the flames begin (kill switch question)

Yep - the switch we have has 1 connection that closes when the other two are open. That has the resistor shorted to ground to save the diodes.

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  • Mulry
  • Mulry
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  • From: Dallas, TX
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Re: Let the flames begin (kill switch question)

If you can wire your secondary set of poles (the primaries are for the battery circuit) so that the poles break the circuit that goes from the "on" position on your ignition switch to the main fuse box, then the kill switch will turn off your car just like turning it off at the ignition switch. This satisfies both the kill switch wiring rule (kill switch must kill both the battery and ignition circuits) and maintains whatever protection for the alt circuit that your vehicle manufacturer originally designed into the car. It's also a hell of a lot easier than figuring out how/why/where to wire in a resistor. YMMV, but this method has worked on my car for the last 2 years without frying any switch or alternator. Good luck.

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  • From: Hayward, CA
  • Registered: 2010-03-23
  • Posts: 1,762

Re: Let the flames begin (kill switch question)

DaveH wrote:

http://farm6.static.flickr.com/5128/519 … d29c_b.jpg

Do this.  Although I hope the big line is going to the starter, not the fuse block.

Did you look at this diagram? WTH? No don't do this. You have the positive going through the fuse block then back to the positive.  This won't do anything. Car won't run, car won't shut off, nada.

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  • From: Hayward, CA
  • Registered: 2010-03-23
  • Posts: 1,762

Re: Let the flames begin (kill switch question)

Judge Phil wrote:

A few teams use a 3-pole (TPST?) kill switch, using one of the circuits to kill the alternator field coil. According to the super-anal freakos who use this setup, you'll spare the diodes if you kill the field at the same moment you kill the output. I suppose you could also accomplish the same thing with a DPST and a relay controlling the field.

Plenty of extra relays in those un-used fuse blocks. Shouldn't be to tough to wire up.

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  • Dave
  • Dave
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  • From: PGH PA
  • Registered: 2009-10-09
  • Posts: 993

Re: Let the flames begin (kill switch question)

I just use a 2 pole 1 for battery 1 for + coil, alternator won't charge if engine won't run.

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  • Serj
  • Serj
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  • From: Cincinnati, OH
  • Registered: 2009-05-02
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Re: Let the flames begin (kill switch question)

ours is a 2-pole Moroso wired in-line with the relay center on our fire wall. car shuts off and won't turn if none of the relays have a hot (+) connection, nor will the system charge. I sweated that thing pretty hard because there was like 4 models of Moroso Kill switches on jegs and i paid more for the one that was specifically listed for cars with alternators (i assumed incorrectly that this was a 4-pole) it sat in it's shipping box in the garage for a work day to come up and kicked myself when i found it wasn't what i was expecting, 2 weeks outside of the return window. Guess we lucked out!

  • From: Land Of Subarus, Colorado
  • Registered: 2009-04-30
  • Posts: 9,416

Re: Let the flames begin (kill switch question)

I've also seen a thousand Lemons cars that don't fry the alternator when they hit the kill switch, so I suspect it might be wise to look elsewhere for the cause of your car's alternaticide.

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  • From: Lost in the Rockies
  • Registered: 2009-10-06
  • Posts: 1,008

Re: Let the flames begin (kill switch question)

We've used the nice Pegasus switch BoB linked to on the Neon and are happy with it, but our buddies with the #45 Jetta went a little simpler and did the 4-pole switch wired as Mulry said (battery wire through one set of poles, ign wire through the other) and it worked fine.

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  • From: Columbus, OH
  • Registered: 2009-05-26
  • Posts: 2,839

Re: Let the flames begin (kill switch question)

One thing that may help is to have a real "ignition" switch on the dash that's just a replacement for the key switch.  You don't *have* to use the kill switch to turn the car off.  Turn it off with the "ignition" switch then, once the car is no longer running, turn the kill switch as well if you want to be double-safe.

We have a cheapie harbor freight kill switch in the CRX and it worked fine without killing the alternator.  Other issues killed the motor first.

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