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Discussion Starter #1
So my mustang is doing something unusual. When I turn the key to the first position (on) it cranks the engine. When I turn it back to the accessory position it also cranks. I'm thinking ignition switch is bad, but here's the thing: The car has been in my garage for 2 months during which time I have done a lot of work on it. T5 conversion, installed dual exhaust, replaced washer pump, replaced headlights, new fuel sending unit, and a lot of other little odds and ends. I really haven't done any major electrical work, mostly just changing out parts, and I'm pretty sure I didn't change anything (other than bypassing the neutral safety switch). I find it strange that the ignition switch would go bad while just sitting in the garage, but I'm sure its possible. Can you guys think of anything else that could cause this?
 

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You said you bypassed the neutral safety switch. How did you do that?
 

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The starter cranks when the starter solenoid is energized by receiving 12v from ign sw. That said either solenoid stays stuck on or ign sw. either has 12v on both sides of its contacts or is shorted. I'd go with ign switch but solenoid is easier to replace. My .02
 

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Discussion Starter #6
Maybe you switched the acc power and ignition wires on the Starter Solenoid?
Thought of that, and I tried switching them the other way, which makes it not crank at all.

You said you bypassed the neutral safety switch. How did you do that?
There are two plugs associated with the neutral safety switch. One going to the switch, and one coming back. Each plugs consists of a male and female side. I just plugged it into itself. I have read from others that have done a C4 to T5 conversion that is how its done (easiest way).

It should also be noted that the solenoid is fairly new (less than a year old). I also don't think its bad because it doesn't crank with the key in the off position. I think if the solenoid was stuck on it would try to crank just by connecting the battery and not even touching the key. Am i wrong?

So really, I am leaning toward the ignition switch. I just wanted some confirmation. My judgement is a little bit clouded by the fact that the car has been sitting inside in one place for 2 months pretty much without ever touching the key. In fact the battery has been disconnected for most of the time. But coincidences happen. One thing I have learned about these old mustangs is sometimes these parts work fine one day, and not at all the next. For all I know this could be the original ignition switch. I'll throw a new one in and see what happens.
 

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Check the connection of your Net switch plug.
It most likely is your problem, you have the backup light connected to the start loop.
That's why when it cranks when your in key on position.
 

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yeah you issue is in your bypass splice or what ever you did. start there b4 anything else
 

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Discussion Starter #9
Check the connection of your Net switch plug.
It most likely is your problem, you have the backup light connected to the start loop.
That's why when it cranks when your in key on position.
Oh. That must be it. Now that I think about it, it certainly wouldn't make sense to have two wires going to, and two wires coming from the neutral safety switch for the purpose of making one connection. One plug must be neutral safety switch, the other must be for backup lights. Also explains why there are no stray harnesses under the car for backup lights. They weren't even connected on my C4. Good, might have just solved two problems here. Thanks guys.
 

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just had the problem with my car today and i fixed it. i replaced the ignition switch EVEN THOUGHT THIS IS NOT THE SOLUTION i just did it because it is old. then when i go into the on position even after replacing it did the same thing. so my mind told me to swap the 2 small wires on the front of the solinoid. it worked. WHY? well if my car is starting on the on postition then that means that the start position got switched with the on possition and the start got switched to the start position. so that means that when you turn the key to the on possition it will crank and get ignition but when you try to stop cranking the engine the ignition will turn off. after i did this everything returned to normal. and if you notice the 2 small letters next to those wire is I = Ignition, S = Starter so Ignition is just giving power to car while Starter starts the car. so if these to are swiched then the ignition switch is giving the power to the Starter while just turning the car ON. hope this came out right and helps you. Simplified just SWAP THE 2 WIRES ON THE FRONT OF THE SOLINOID this is almost a garanted fix.
 
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