1 Topic by aventari (edited by aventari 2016-05-02 08:23 PM)

  • From: San Diego
  • Registered: 2015-05-03
  • Posts: 147

Topic: Can I use a 4 pole kill switch without killing my alternator?

The car is a 93 Accord I bought a few years ago already built.
My alternator just started acting flaky and I think the way the previous owners wired the kill switch is feeding back and killing the diodes.

It has this switch
http://i.imgur.com/Zn8W0TL.jpg
details: http://www.longacreracing.com/products. … +Terminal+

And it's currently wired like this:
http://i.imgur.com/dxsgrxI.jpg


Is there a way to wire this up to use a resistor to do it properly, or do I need a 6 pole switch?





The Longarce site shows this for instructions, but I don't think that will properly kill the motor because the energized field will keep current flowing into the electrical system. If this worked for Lemons I would think more people would do it.

http://i.imgur.com/ZQfq0Nq.jpg

Takata R&D :: 1993 Accord - team captain - rear drum brakes lol
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  • From: Seattle-ish
  • Registered: 2011-06-16
  • Posts: 654

Re: Can I use a 4 pole kill switch without killing my alternator?

I don't have any experience with that particular switch, so I don't know exactly how the contacts are working, but the one we use not only disconnects the battery completely, but also shunts the alternator output through a load resistor to ground, effectively killing all power to the car. 

Here's the wiring diagram:
https://www.pegasusautoracing.com/Images/L/4430-inst.jpg

I'm sure others will correct me if I'm wrong, but I don't think that Longacre switch can be wired in the same manner.

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  • From: San Diego
  • Registered: 2015-05-03
  • Posts: 147

Re: Can I use a 4 pole kill switch without killing my alternator?

Yeah that's the one I think I'm going to have to get and use if I can't figure out a good way to rewire mine.

I've been looking up zener diodes and a product marine guys talk about called zap-stop but it seems to be one time use only, like a fuse
http://www.cruisersforum.com/forums/f14 … 29442.html

Takata R&D :: 1993 Accord - team captain - rear drum brakes lol
GoPro 360 Heros :: BMW E28  - co-captain

4 Reply by meyers0150 (edited by meyers0150 2016-05-03 10:11 AM)

  • From: South Jersey
  • Registered: 2013-12-01
  • Posts: 588

Re: Can I use a 4 pole kill switch without killing my alternator?

Here is a post from the lounge depicting a legal single pole switch.
https://www.facebook.com/photo.php?fbid … mp;theater

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  • Registered: 2012-11-27
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Re: Can I use a 4 pole kill switch without killing my alternator?

meyers0150 wrote:

Here is a post from the lounge depicting a legal single pole switch.
https://www.facebook.com/photo.php?fbid … mp;theater

This is it.  Alt remains connected to the battery, but the entire chassis is shut off.  Kills the ignition and stops the engine.

  • From: San Diego
  • Registered: 2015-05-03
  • Posts: 147

Re: Can I use a 4 pole kill switch without killing my alternator?

That's interesting. It would work, but can the battery react fast enough to absorb the transient voltage spike from cutting off the alternator from the main current path?

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  • From: South Jersey
  • Registered: 2013-12-01
  • Posts: 588

Re: Can I use a 4 pole kill switch without killing my alternator?

I've done it that way on 3 cars now with no issues.

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8 Reply by firegremlin (edited by firegremlin 2016-05-03 02:44 PM)

  • From: Rockville, MD
  • Registered: 2010-12-15
  • Posts: 1,154

Re: Can I use a 4 pole kill switch without killing my alternator?

... Interesting, somewhat related tidbit: on the Fury, I've experienced unusually long shutdown times with the two-post kill switch (up to 3 seconds of a slowly dying motor). Finally traced it down to the massive radiator fan we use, and very little other electrical load. When you shut down the car, the fan has enough inertia to keep spinning for a bit, and now acts as a generator. With the fan off, shutdown is instantaneous. Wiring in headlights helped a lot; I wonder if this problem can be fixed completely by putting fan on a relay, or if I need something more complicated.

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Re: Can I use a 4 pole kill switch without killing my alternator?

You can wire in a resistor to the alt power wire (alt side) to prevent spikes. The resistor will get hot whenever the kill switch is on and will kill the battery if you forget to turn off the kill switch.  Theres a chance the resistor will burn out.  I've seen these start electrical tape on them smoking...

You can maybe (depending on your interpretation of the kill switch rules, "All electricity must be interrupted by the kill switch" or their intentions?) leave the battery wired to the alternator. The battery connected to the alternator will keep the battery safe. But the kill switch wont kill power to your alternator which could be balled up in a crash. A corner worker or driver could hit the kill switch but not be able to disconnect power to the alt wired this way.

6 post is nice because there is the extra switch to be able to kill injectors or the coil to positively kill the engine (keep other stuff off that switch to prevent power back feeding.) 

You can get run on from auxiliaries spinning down and feeding power back into the system if the circuits aren't broken out /separated well.  Even with relays the auxiliaries can still back feed. The power has to drop enough for the relay to drop out (typically below 7-8 volts) to disconnect the aux power source that is doing the back feeding.  Basically a relay wont help unless its coil power is broken out from the back feed source to be able to disconnect it.

-Killer B's (as in rally) '84 4000Q 4.2V8. Audis never win?

10 Reply by aventari (edited by aventari 2016-05-03 03:25 PM)

  • From: San Diego
  • Registered: 2015-05-03
  • Posts: 147

Re: Can I use a 4 pole kill switch without killing my alternator?

^^^ heh interesting!


So it occurs to me I can just put an SPDT relay on the alternator wire before the switch.  The SPDT relay will switch open with ignition power (leave 87 disconnected)  and when not powered can be grounded through a 3 ohm resistor (or a 1157 light bulb heh) connected to 87a

https://www.futurlec.com/Pictures/HORNRELAY_SPDT_CIRCUIT.jpg

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Re: Can I use a 4 pole kill switch without killing my alternator?

That could definitely work.  I'd put a small light bulb on the alt for testing to make sure the relay does what you want it to do when you shut it off to protect the alt.  Then remove the test bulb when you know its right.

-Killer B's (as in rally) '84 4000Q 4.2V8. Audis never win?

12 Reply by Mulry (edited by Mulry 2016-05-04 07:53 AM)

  • Mulry
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Re: Can I use a 4 pole kill switch without killing my alternator?

If you are retaining the factory wiring harness for your Accord, there is a very easy way to do all of this. I've used that same Longacre switch on all my builds, this is how I wire all of them, they always pass tech, they always work, and I've never nuked an alternator. I'll try to keep this short since I don't have good drawing tools access right now.

1. There are 4 lugs (or posts) on the switch. Two are larger and two are smaller. Use the larger two for your battery feed, as indicated in the drawing in post 2, above. Just run the battery to the first post and then out of the second post to wherever the factory wiring harness has battery power connecting to main power.

2. The smaller 2 lugs will intercept your ignition circuit. The key for your ignition has 2 wires going into it. One is 12v+ hot all the time, one is hot only when the key is in the "on" or "start" position. Intercept one of these wires (it doesn't matter which one) through the smaller 2 lugs. Thus, when the kill switch is thrown to "off," to the car it looks just like you turned the key to "off" and will take advantage of the system that the factory built into the car for when you turn the car off.

Many other wiring systems make sense, but I've found that this is the least complicated implementation if you are retaining the factory wiring harness and electrical system. Good luck.

Pat Mulry, TARP Racing #67

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