View Full Version : [How-To] Manual Neutral Safety Switch

03-28-2013, 03:45 AM
Notice: Neither I, nor CelicaTech, its owners, nor any of it's members, partners, or affiliates, etc. are responsible for or liable for what you do with this information. It is provided in the hopes that it will be useful, but with no guarantees (even implied ones) of fitfulness for any purpose. It is left up to you to ensure that doing this modification is legal in your area, and that you operate your vehicle safely.

First I want to give credit where credit is due. Grayscale was the first person (I know of) to do this: here (http://www.celicatech.com/forums/showthread.php?24832-ST185-Clutch-Safety-Switch&p=283268&viewfull=1#post283268), and inspired this implementation, as well as showed what wires to use. I think that grayscale's solution is *better* than mine, however, his requires welding (which I cant do) and a plastic shift base (I have the metal one), so I came up with an alternative method.

Second, make sure you read and understand completely what is being explained here. This can hurt you, your property, your car, or your loved ones if you do a half-assed job of it. Ask questions if you're unsure!

Supply list:
- 1 reed switch ($5 at Fry's)
- some wire (16 - 20 gauge), preferably two colors (mine is red and black)
- a magnet ($2 for three at Lowes)
- some 1 minute epoxy ($5 dollars at Lowes)
- some ring terminals
- a multimeter
- a way to join wire (solder, butt crimps, magic, etc)
- optional: a harness out of a junk yard
- optional: sandpaper (~600 grit)
- optional: denatured alcohol

Reed switches are a magnetically triggered switch often used to know when a door has been opened or closed. If you've ever worked around trash compactors or cardboard bailers and wondered how they know the door is shut, wonder no more.

Now, there are two ways you can mount your switch on a 5 speed, either horizontally across 1, 3, 5 and 2, 4, R; or vertically across 1, 2 and 5, R. On a 6+ speed you will need to mount horizontally across multiple gears. I mounted mine vertically, because the stock shifter in the 5th gen actually runs into the part mounted toward the rear of the car. If your shifter was straight this would not be a problem.

Mount your reed switch. Most use screws or double sided tape. If you use double sided tape use sandpaper to rough the surface up, and then use denatured alcohol to thoroughly clean the surface. Denatured alcohol is the right cleaner because it dries residue free.
Similarly find a place to mount the magnet on the shifter, be aware of the bolt heads that hold down the shifter base.

This is the really crucial step, you need the magnet in a position such that when the car is in gear (read: not neutral) that the current flows between the com terminal and nc terminal, and when in neutral (not in gear) that current flows between the com and no terminal. Use your multimeter to test this. If this condition is not true, you need to adjust the position of your magnet. If you fail to do this the car will either: a) not start at all (best situation), or start in all gears (BAD), or in some gears (VERY BAD).

When you have found a good place mark it (I used some electrical tape I had handy) you're ready to mount it. There are two obvious ways to mount the magnet: You can get magnets with a hole in them, drill and tap a small hole and use a screw and washer to hold the magnet down. Alternatively I used 1 minute epoxy, because I can quickly clean this up and take it back to stock, and not worry about having a hole in my shifter. If you use epoxy, sand and clean the surface with denatured alcohol before applying the epoxy. When the epoxy gets tacky, ensure that the shifter can still get into all gears (especially second), and that you still have current between com and nc when in any gear, and from com to no when in neutral.

Now the wiring:
The switch will have three terminals on it, labled com (common), nc (normally closed) and no (normally opened). We will be using the com and no terminals.

This is the harness that attaches the switch to the clutch. Grayscale has a much better picture of this: here (http://www.celicatech.com/forums/showthread.php?24832-ST185-Clutch-Safety-Switch&p=283268&viewfull=1#post283268)
Personally I want the option to take this back to stock with zero effort, so I paid $2 to get into pick n pull and found the harness there, but you could also just cut and use the harness in the car. Attach a wire to the no terminal and a second to the com terminal and run them either under the carpet, or through the dash to the other side. I ran mine through the dash.

Attach the wires to the female side of the harness, I recommend solder and heatshrink. Run black (you can use whatever colors you want, but this matches my pictures) to your com terminal (this ground), and red to your no terminal (this is hot). Attach the red wire to the green with a red dot (the male harness is White/Black), and the black wire to to Green with red and black dote (male side is Black). You can attach your remote start neutral safety wire to the no terminal. Then plug in the harness.

To test: put the car in neutral and attempt to start it. If it starts you are half way there. Put the car in gear, ENGAGE THE CLUTCH (if this didn't work right you don't want to start in gear!), and attempt to start the car. If the car does not start in any gear, you're done. If it starts in a gear you will need to adjust your magnet. If you messed up, you probably didn't test as you go, like I told you ;)

You're done! :yay:

03-28-2013, 08:37 PM
brilliant idea! le Prelude got an auto start and then a five speed swap, so right now it can start in gear if left in gear. this is a great way to prevent that.

03-31-2013, 12:44 AM
this gave me an idea to make circuit boards w/ reed switches on them to do this in a more compact fashion...

03-31-2013, 04:04 AM
Are you going to sell this more compact version?

03-31-2013, 05:43 AM
im going to be overseas in 3 months... probably not.

I could build a kit or something and have it drop shipped via component perhaps?