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Wirtz
12-03-2006, 12:23 AM
This is not really a rules question, but I was not not sure what would be a better forum to put the question in;

My car is a 3rd gen TPI car but I think this applies to any computer controlled car. Are people running a master kill switch that only cuts the positve power or one that also connects to the alt and coil? Check this link for the wiring diagram.
http://www.pegasusautoracing.com/Images/L/4430-inst.jpg
So circuit 1 grounds out the alt and circuit 2 cuts the coil power I think?

Are both of these connections needed? I was looking at a buddies SRF (also factory computer controlled) and it only has the battery line through the switch.

Thanks,
Jeff

marshall_mosty
12-03-2006, 12:27 AM
Basically, all the electrical power for the car (minus fire system) should be switched through that switch.

That diagram is confusing, in my opinion.

GlennCMC70
12-03-2006, 01:13 AM
the reason for the 4 post set-up it to kill the voltage to the field windings. it is possible for the alt to continue to put out 14 volts and feed back to the feild thru other wiring. if the field wire is isolated thru the small two posts (by the way , they are not connected to the two large posts in any way internally), the circuit is opened and and the output from the alt cant feed back to the field wire. my field wire is broken in two places. one w/ a toggle on the dash as part of the ing switch and the other is on the master kill. you want to be sure the field does not get constant voltage. i've been told it will kill the alt. (i think the voltage reg will die). the way my car is wired, my master can stay on 24/7 and will not drain the battery. it also keeps the memory on the PCM.
my car is a 4th gen by the way.

GlennCMC70
12-03-2006, 01:17 AM
that switch is differnt in that is a 6 pole switch. the 4 small posts are set up to be 1 open and 1 closed @ all times. they swap conducting/not conducting as the master is turned on/off.

conducting = closed
non-conducting = open

hope i didnt "dumb it down" too much, but i dont know your knowlege base.

Wirtz
12-03-2006, 02:49 AM
Thanks guys,

I think I got the basics, though I admit wiring is my least fav part of this game. My plan was a master kill in the window with the only connection to the battery through this switch, and a ign / start switch on the dash.

From the wire diagram, pole #1 grounds out everything on the car side of the master when it is in the off position (therefore including the alt I would guess). Otherwise I had not planned on modifying the field wire at all. I am using a Painless engine harness, and I had planned to just leave it alone. If I do that, the engine will shut off when I switch off the ign / start switch on the dash right?

Pole #2 opens the circuit when the switched to off, in this case breaking connection to the coil. This maybe be a good idea in practice, but I'm not sure I need to do this. My reason to not do it is not laziness, but it just seems to be 2 more long wires I have to run that might go bad at some point and give me fits trying to trouble shoot. KISS and all that good stuff.

My current thought is to connect the car side of the harness back through pole #1 as suggested in the diagram, but to not use pole #2.

Your post brings up another good question, what are guys doing for the ECM wiring? Do you run 12v always to it so it keeps it's memory, or do you hook it through the master switch so it loses power whenever the master switch is off? I was planning to run my ECM through the kill switch.

Thanks,
Jeff

marshall_mosty
12-03-2006, 08:17 AM
Jeff,
My computer loses power every time I kill the car. It doesn't seem to hurt anything.

GlennCMC70
12-03-2006, 10:28 AM
Jeff there is more that one way to do it for sure.
my painless harness came w/ nothing for the Atl wiring.

macstang
12-04-2006, 04:44 PM
my field wire is broken in two places. one w/ a toggle on the dash as part of the ing switch and the other is on the master kill.

[b]8.11. Alternators
The alternator must be OEM stock. The alternator must be charging according to the manufacturer's specifications. Other than the main electrical master switch, any type of alternator cut off switch is prohibited.


Hmmm..... so what are you saying Glenn???

Al Fernandez
12-04-2006, 05:01 PM
Jeff, this is actually a very good topic, and one that throws a lot of people off. Are you sure in your car everything is grounded via the switch? Every car I've seen has ground straps on the block, PCM, bla bla bla and the hot side of the battery going through the main cut off switch. That results in the car being able to run when you turn the master off, which is bad.

Cutting power to the coil is one way, but as Glenn has said somewhat violent. I prefer cutting the excitation current to the alternator. That eliminates it as a source of juice, and the motor dies.

By the way, and this is not an AI or CMC thing, but rather a NASA CCR thing...which states "The switch shall cut all power except to the on-board
fire system and any other life support / medical device." Now, I've only seen officials check this by firing up someone's car, throwing the switch, and seeing if the motor actually dies. I've never seen someone actually put an amp meter on the battery to see if anything is drawing current, but that is not to say they wont at some point in your racing career.

Fbody383
05-02-2008, 11:31 AM
This seemed like a good place for this.

Does the main power feed to the starter motor have to run through the master disconnect switch?

The solenoid, key/switch start feed, wiring will be but I wasn't sure if I had to flow starting current through the switch.

GlennCMC70
05-02-2008, 11:58 AM
the switch should be placed as to limit the number of things that still has power on it once the switch is turned. so yes, i would have everything in the car wired to a point after the switch.

AI#97
05-02-2008, 12:22 PM
This seemed like a good place for this.

Does the main power feed to the starter motor have to run through the master disconnect switch?

The solenoid, key/switch start feed, wiring will be but I wasn't sure if I had to flow starting current through the switch.

Nope. the + feed to the starter should NOT go through the disconnect especially if your disconnect is not rated for 400+ amps. Technically, by electrical guidelines, since the solenoid is the disconnect for the starter, and your starter solenoid would be disconnected by the Master switch, you are good to go...

Installation of my master switch took some time to figure out because of the way the power feed hits the distribution block. I had to separate the alternator feed from the power block and run it through the master switch, and then back feed all power as a "T" to the block and then the + side of the battery. Not what I would prefer but it works and is safe.

Good luck!

Fbody383
05-02-2008, 03:09 PM
Does the main power feed to the starter motor have to run through the master disconnect switch?

Nope. the + feed to the starter should NOT go through the disconnect especially if your disconnect is not rated for 400+ amps.


the switch should be placed as to limit the number of things that still has power on it once the switch is turned.

Glenn, I'm just poking you with a blunt rookie stick. I agree with Matt and would hate to have a master disconnect fail while starting the car. It's always bad to let the smoke out of an electrical system. :shock:

I dropped you a PM; I'm trying to get some wiring done this evening and would prefer to run the starter motor only directly to the battery.

GlennCMC70
05-02-2008, 04:03 PM
so in a worst case senario...... the car is wrecked and fuel is spilling. the switch is flipped but sparks are still flying due to the starter motor feed that cannot be disconnected w/out tools.

my starter draws thru my switch and always has. i've had the same switch for 3+ years. turn the switch and there is no power on anything but the cable between the battery and the switch.

Fbody383
05-03-2008, 12:28 PM
so in a worst case senario...... the car is wrecked and fuel is spilling. the switch is flipped but sparks are still flying due to the starter motor feed that cannot be disconnected w/out tools.


I agree that this is a valid concern. The switch I had crapped out before it even had load on it, detents went soft. Gotta love plastic.

Glenn, which switch do you have?

Wirtz
05-03-2008, 03:55 PM
Just my $0.02, I agree that you want everything through the switch. That is really its purpose.

You didn't ask, but I am using one from Pegasus.
http://www.pegasusautoracing.com/productdetails.asp?RecId=1464
I do think a good master kill is worth the few extra bucks.

I think want the versions like this one with the extra poles so you can cut fuel, coil, or alt like suggested in this thread.

Jeff

jeffburch
05-03-2008, 05:18 PM
My car had that one when I got it.
I replaced it with the same.
Recent electrical issues required shotgunning the altenator, battery, master switch and some other stuff.
I'm on my third master kill switch.
Everything goes thru it.
$57 and worth it.
jb

AI#97
05-03-2008, 06:11 PM
looking back at mine, the feed to the starter does go through switch...for some reason I remember it feed from elsewhere in the harness...? I am using a simple $35 painless switch...works great, been in the car for 4 years but I don't really turn it off much.

mitchntx
05-03-2008, 07:28 PM
I used one of these ...
http://www.pitstopusa.com/detail.aspx?ID=9745

I had charging issues at Houston and needed to see if the switch was bad and bought one of these (hey, I was grasping at straws) ...
http://www.jegs.com/i/Moroso/710/74102/10002/-1

The Moroso unit is very robust. I like the way the case is molded to shield and protect the terminals.

Fbody383
05-04-2008, 03:03 PM
Just my $0.02...

Wirtz, as clean and well prepped as your car is, I'll always consider your opinion.

I think I'm going with the Moroso switch too; if they put as much thought on the internals as shielding the outputs, it probably pretty good.

Thanks for all the info guys.

ps - remind Ross I'm further along than he is. 8)