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Ignition Switch

A

AtlantaSteve

Active Member
I don't want to go into too much detail about what I'm planning with my starter switch (Nothing secret, just want to get the bugs worked out before I say too much) but basically, I will not be using the stock ignition switch at all in my car when I'm done.

Going over the ignition switch it looks like, when the car is in the IGN position, the "C" terminal feeds the coil through the resistor, and the Screwed Lug on the back of the switch feeds everything that uses keyed power from the switch (gauges, turn signals, etc).

From an "electrons passing through copper" perspective, what is the difference between the "C" terminal and the lug? it seems both are powered on and off at the same time, and both get powered from the same input, so in theory, I should be able to power both the coil, and all the "keyed switch electrics" (not accessories, but things that are only powered when the switch is in the "ON" position) from the same circuit, correct?

Thanks
 
I'm sure Midlife will chime in with a definitive answer. But I think that the center lug is also hot when the key is in the accessory position. It's been a little while since I worked on my ign. switch, but I think that the "C" terminal is hot when starting and the center is not -- hopefully I don't have that backwards.

-rob
 
I haven't started doing all the fun multimeter checks on the actual harness yet, but looking at the wiring diagrams, it SEEMS that the turnsignals and gauges are driven from the center lug, and I know that those are not powered in ACC.

The ACC terminal, I believe, is B, which covers things like the radio. Obviously, the ACC circuit is hot when the car is switch is in the "Run" position, as well.

I dunno, we'll wait on the word from Mid :)
 
I just found an old wiring diagram, and this is how I read it: the B lug should have the yellow wire coming from the battery, and it constantly hot. The S lug is the starter, goes through the neutral safety switch. The C lug only goes through the pic resistor wire. And it looks like every thing else goes through the A lug.

Now, you've got me curious. So, it will be good to hear from the authority. :craz
 
You guys are mostly correct.

There are four positions for the ignition switch.

OFF: only those essential parts of the car are powered with the key out of the ignition: cigarette lighter, courtesy lights, and things like that. They get their power directly from the battery and fuse box.

ACC: Everything on the car gets powered up except the coil and the starter. For early Mustangs, the Voltage Regulator is energized, but after 1969, it is tied to the RUN position.

RUN: Adds to the ACC powered items: the coil (and Voltage Regulator for 1969 and later).

CRANK: Adds to RUN the signal to energize the starter solenoid so the car can crank. This also bypasses the pink resistor wire so that the coil gets full voltage from the battery.

Simple, eh? A door bell chime is more involved and complicated...
 
"Midlife" said:
You guys are mostly correct.

...

Simple, eh? A door bell chime is more involved and complicated...
Click to expand...

You are the man!! Just what I needed.

Just a quick clarification, in CRANK , are the ACC powered items not de-energized? It's been an unfortunate amount of time since I last cranked my mustang, but last I remembered, the radio and such would turn off during the crank sequence.
 
So, midlife, could you break down what lug on back of the ignition switch does what?

So...how does a door bell chime work? :craz
 
"johnpro" said:
Yes. ACC powered items are de-energized in CRANK.
Click to expand...

OK glad my memory isn't completely failing me. Thanks for the clarification.

Gotta add yet another relay to my design, LOL.
 
"66gt350" said:
So, midlife, could you break down what lug on back of the ignition switch does what?

So...how does a door bell chime work? :craz
Click to expand...

The big lug on the back of 1964.5-1967 ignition switches is the ACC post.

Huh...I never thought about the ACC lines being unergized while cranking, but the schematics show that that is the case. Well, you guyz taught this old dog a new trick! It makes sense, as you want as much voltage/current going to the starter as possible; voltage/current draws for un-necessary items would reduce your cranking potential.

Oh...how does a door bell chime work? You press a button and little tiny fairies inside become aroused and make lots of noise.
 
While I have nothing of value to add to this thread, Steve has definately peaked my interest.... :pop
 
"Havok1" said:
While I have nothing of value to add to this thread, Steve has definately peaked my interest.... :pop
Click to expand...

"apollard" said:
I'm guessing a 'modern' push button start- but I'm pretty curious too-
Click to expand...

Honestly, I'm not trying to make it sound top secret. I don't mind saying :) It's just that I've seen this topic blow up on other message boards, and I'd rather have the bugs worked out, before I suggest that I solved the problem.

But basically, I won't NEED a key at all. It'll be push button start, using RFID to identify me. When the car is turned off and the doors shut, after a short timeout, it will lock the doors, and disable the ignition. Also if I leave a 3 meter perimeter around the car, it will lock. When I return to the 3 meter perimeter, the doors will unlock, and the ignition will be enabled. Because I love the race-car style switch panels, I'm going to have a toggle switch that will turn on the ACC, and arm (but not turn on) the IGN. When I push the start button, the IGN will be energized, and held high, and the starter will start turning. Once I let go of the button, the starter will stop, but the IGN will remain energized. When I switch the toggle off, the IGN and ACC will be killed, and the starter disabled.

If I am outside the perimeter of the car, it will be impossible to start, short of jumper wires. (Car will still be vulnerable to the typical under-hood attacks)

If someone "carjacks me" I'll keep the RFID in my pocket, and as the car drives out of my range, it will continue to run to allow the criminal to get a safe distance from me, and then die.

I'll also have a keyed switch hidden in the interior I can use to override the alarm, in case it gives me problems, and still drive the car.

Mostly I wanted a way to not use a key at all, like a modern car, and I THINK I have it mostly figured out. We'll see.

I still have a lot of parts left to buy, so it'll be a while before I try this.

Steve
 
I kinda figured that where you were going with it. Cool idea. I'll keep an eye on it to see how it comes.
 
"AtlantaSteve" said:
But basically, I won't NEED a key at all. It'll be push button start, using RFID to identify me.
Click to expand...

I've been accused of being an electronics geek* for using MOSFETs for everything.

Darn. RFID. :wor

*If you are one, that's a compliment.
 
"apollard" said:
I've been accused of being an electronics geek* for using MOSFETs for everything.

Darn. RFID. :wor

*If you are one, that's a compliment.
Click to expand...

Don't get too impressed...most of the RFID based stuff comes with an alarm system I picked up. It's designed to still work with a keyed system, but I think that it will offer just enough protection that I can switch to unkeyed and still be safe. My work is all really being done with the relays that will drive the ACC/IGN/and Start circuits.
 
I'm planning on RFID'ing my door bell: only those that have the proper key will be able to ring the bell. Smart, eh?
 
"AtlantaSteve" said:
Don't get too impressed...most of the RFID based stuff comes with an alarm system I picked up. It's designed to still work with a keyed system, but I think that it will offer just enough protection that I can switch to unkeyed and still be safe. My work is all really being done with the relays that will drive the ACC/IGN/and Start circuits.
Click to expand...

Great idea. What alarm system is it?
 
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