Master kill switch wiring

[Wirtz]

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]

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]

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]

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]

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]

Jeff,
My computer loses power every time I kill the car. It doesn't seem to hurt anything.

[GlennCMC70]

Jeff there is more that one way to do it for sure.
my painless harness came w/ nothing for the Atl wiring.

[macstang]

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]

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]

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.