Start Switch

02/01/2022

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Push Button Start

This is a mod that I have been asked for a number of times by people wanting to have push button start on their supra.

This mod will give you the ability to start the car by a push button but, will still keep the security of having a key in the ignition and uses the factory ignition switch to control power to the car still.

To operate the system you would insert the key as normal, turn to the ignition to the on position (II) then press the button to crank the engine. Turning the key to off switches everything off as normal.

Its a simpler system than the transponder system I use on my car which removes all the factory switching completely.

Its pretty simple mod carried out under the steering column where the ignition switch plugs into the main car loom. You will need to remove the panel with the vent in above pedals & locate the large black connector from the ignition barrel.

DISCONNECT THE BATTERY!

We are dealing with BIG current here so its imperative you disconnect that battery for this mod! Where there are fuses marked on the diagrams FIT THEM! If you don’t and a fault develops wires could easily melt and cause a fire resulting in charred car & a mess on the drive! You have been warned!

I have detailed three ways in which you can carry out this mod, the first one allows you to use a low current switch to start the car & assumes the car is not fitted with a starter relay nor has been modded with a starter relay (Rogers relay mod if from MKiiisupras)

It involves fitting a relay to do the high current switching and using a small switch to energise the relay. The LED is optional but, that part of the circuit may be applicable to you if you have a start switch with a light built into it.

The relay needs to be mounted close to the ignition connector and any wiring in RED must be of large gauge to handle the power. Cables after the fuse or other colours can be of far smaller gauge as these take small current.

Find somewhere to mount your switch, this needs to be a momentary contact push switch (like a door bell switch) NOT A LATCHING SWITCH! Some suggested places for mounting are gear shift, coin slot, cigarette lighter hole etc.

Splice into the car cables & solder the joins then insulate them well, don’t cut them if at all possible as they are large and carry a lot of current so to keeping them intact is good practice & avoids messy joints of large cables.

The Black / White wire can either be left intact so the push button and the standard key will crank the car or cut and insulated to stop the standard key switch cranking the car - the choice is yours!

The second diagram shows how to wire the system by using a high power switch designed to switch large currents in a car without a starter relay.

This last diagram shows you how to wire the switch if your car has a starter relay fitted already or has been modded to incorporate a starter relay (Rogers relay mod from mkiiisupras)

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