Alternator Wiring with Kill Switch

[jefflock]

I have a one wire denso alternator that I want to put on my race car. I have the standard kill switch at the back of the car. Also using a ford style solenoid. I had it on and running but the kill switch won't kill it. How do I need to wire it to make the kill switch work?? Thanks Jeff

 

[1969383S]

Sketch out a basic schematic for us of your setup.

Could be as simple as adding a diode.

 

[67Dart273]

Frankly (I think) the easiest way is with a 4 post (double pole) kill switch. If you look around, there now exists several brands that offer good, heavy duty switches in 4 pole. I'll look later, I thought I had one bookmarked

Anyhow, run two light gauge wires from the small accessory terminals on the kill switch up to the front. Use them to break a relay circuit, with EFI you can break the pump relay, otherwise break the ignition. If you run MSD you don't need a relay.......just wire those to in series with the "small red" switching wire on the MSD

Many guys run a separate no6 or so charging line direct to the battery. In my opinion this violates the rules. They say "kill all power" or words to that effect...... It certainly is not patently "safe." That leaves a pretty big welding lead ?? hooked to the battery, live.

 

[dusterdragracer]

Just run a # 8 or # 10 wire to the battery around the batt.cut off switch from the alternator. Put a 50 amp or better auto re-settable breaker on the wire. You can get it at Napa.
Put a boot on the alternator back, as it will be constant hot.
But 67dart273 is correct too. This just saves a $80.00-$100.00 4 pole switch purchase.
Lastly, a diode would have to be huge to handle the load. But possible if you can find one.
You could use a RV type solenoid (one that can handle constant voltage) that will activate from your ignition switch. But you still need to run a wire around the batt. switch.The solenoid will kill the voltage on the wire when the ign is off.

 

[fishy68]

I agree with Del that a 4 pole switch makes it a lot easier. A buddy of mine just bought this 4 pole unit from Summit for $35.

http://www.summitracing.com/parts/anp-4polesos

I'm helping him wire it and my plan is to use the 2 small terminals on the kill switch to operate a small relay that kills power to the ignition system. If you wire it to kill the ground side of the ignition relay it's as simple as grounding one of the small terminals on the kill switch and running a 16 ga. wire from the other terminal to the ground terminal on the ignition relay. Fuse it for safety of course. Doing it that way all you have is the main power feed running to the starter/alternator and 1 wire to operate the ignition relay. If you don't want to wire in a relay you can do it Like Del said and use just the 2 small terminals on the switch to kill power to the ignition system. For that you need to run heavier wiring and of course fuse it accordingly to how much the system draws. Hope that helps Jeff

 

[pettybludart]

Get a 4 post as mentioned,it makes things easier and safer.

 

[dusterdragracer]

With all due respect. Who wants a relay, or any circuit that would require cutting into the ignition system wire. Especially in race application. Relays fail, even the best Bosh ones.
Just run the quad post cut off switch, making sure it is rated at the proper amps your alternator is going to put out. Look close at the amp rating on the switches (on the alternator side, not the batt. post side). The turbo one says 240 amps, but that is for the batt. side. I doubt those small posts will handle a large amount of amps. I am running a 75 amp. alternator, most the switches when I researched them, could not carry that much amp. At $35.00, I doubt that one does.
This is the one I run:
Longacre Racing 45782 - Longacre Racing Products Battery Disconnect Switches

$69.00 Jeggs

 

[67Dart273]

With all due respect. Who wants a relay, or any circuit that would require cutting into the ignition system wire. Especially in race application. Relays fail, even the best Bosh ones.

I guess you haven't looked at modern cars, lately LOL. Relays everywhere. Most certainly in the ignition, charging, fuel system.

 

[rmchrgr]

Continuous duty solenoid! Pretty much the only way to do what you want with the switch wired like NHRA wants it (B+ side).

It gets wired it between the alternator charging wire and the cutoff switch. The solenoid operates only when fed B+ from the battery and allows the alt to charge the battery when it's on. But, when you throw the switch it shuts off the solenoid thus stopping the charge circuit.

They are like $50 or so and can handle a lot of current. They look like a Ford starter solenoid but are slightly different.

I have the Denso alt. too, this setup works correctly. It was a pain to figure out, was very confusing to me at first but once I realized what the solenoid does it all made sense.

The CD solenoid is the chrome one on the left.

 

[dusterdragracer]

I guess you haven't looked at modern cars, lately LOL. Relays everywhere. Most certainly in the ignition, charging, fuel system.

But yes, they do fail too.Your talking modern street cars, not drag race cars. If you need a batt. cut of, then most likely it is a drag car....Simpler, the better.
I have lots of relays, my fans run on thermos's with relays, different ones for different temps. My back up lights and trans brake, back the car up via reverse light switch in the shifter via relays, even though the reverse lights don't come on when the transbrake engages. Think about wiring that up for a min. My car is full electronics. I even get more exotic then that......Have you worked on a 2 million dollar RV wiring?...You want to talk about relays....LOL
I never touch a switch, or need to remember to tur a switch on when racing.
I would never interrupt my ignition, with a relay.....Have wired at least a 100 cars for street and race both...Who knows how many motorhomes I have had to straighten out.

Back to the original question...Just install a 4 post battery disconnect capable of the amp rating of your alternator, ignore all the other postings including mine!...

 

[dusterdragracer]

Continuous duty solenoid! Pretty much the only way to do what you want with the switch wired like NHRA wants it (B+ side).

It gets wired it between the alternator charging wire and the cutoff switch. The solenoid operates only when fed B+ from the battery and allows the alt to charge the battery when it's on. But, when you throw the switch it shuts off the solenoid thus stopping the charge circuit.

They are like $50 or so and can handle a lot of current. They look like a Ford starter solenoid but are slightly different.

I have the Denso alt. too, this setup works correctly. It was a pain to figure out, was very confusing to me at first but once I realized what the solenoid does it all made sense.

The CD solenoid is the chrome one on the left.

Thanks, exactly what I was talking about, but I believe they are less then $50.00. Just be careful, exactly what rnchagr says. It needs to be continuous duty, not momentary.....Chris

 

[67Dart273]

Back to the original question...Just install a 4 post battery disconnect capable of the amp rating of your alternator, ignore all the other postings including mine!...

The problem is there may be no such thing. I don't care what ratings claim. There are lots and lots of lies told about ratings.

I really don't get your opinion, here. Christ, there are lots of guys running EFI. There's at least a couple of relays involved in all of them. And, "it just might be" that relays are far more reliable especially when voltage drop is figured in, than any ignition switch used in these cars. On top of that there are plenty of rocker / toggle switches that fail.

Your starter has at least one relay.....it's called a solenoid. If you run an automatic, you might have a second one called the starter relay. Now we're up to at least three already, for a simple car with an electric pump and carb.

Yes "**** fails." Even mags fail.

 

[rmchrgr]

Also using a ford style solenoid. I had it on and running but the kill switch won't kill it.

Just re-read your post here and I think you may be confused as to what the 'Ford" solenoid does - it's generally used for the large B+ wire that goes to the starter. It "only allows the B+ wire to be hot when cranking", or so the saying goes. Once the car is done cranking and is running, the solenoid goes dead, the only hot wire left is the B+ wire to the lug on the solenoid. And if you have the switch wired correctly, that wire will be dead as well when the switch is thrown.

I used it because I liked that idea and wanted to run the wire inside my car. If it's a race-only car, you could probably get away with it outside tucked up under the frame rail to the starter but mine's a street car so I wanted it inside. The caveat to having it inside and live all the time is that it's a potential hazard - it's a big wire with a lot of current flowing through it. If it gets shorted etc., it could be a big problem with fire.

The CD solenoid really has nothing to do with the Ford solenoid, they handle two separate issues. You can have one without the other, both or neither depending on how you have your cut off switch set up. I just happen to have both mounted in close proximity because they need to be close to the switch and battery to do their thing.