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Cornwallfrank

Fia Cut Off/kill Switch

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Cornwallfrank

Hi all, having wasted my money, albiet about a fiver on a battery cut of switch, realise that this doesn't " kill " the engine, now i have bought a better item, but have a couple of questions if anyone can help.

The new "FIA" appproved switch has two large terminals, + and - battery lead, and four spade terminals.

In my mind the diagram with the switch is over complicated, or I'm not seeing the right way.

The switch came with a resistor to go to earth to prevent alternater damage due to over run.

Surley, and excuse my ignorance, if I put the main ignition + through the terminals that cut off when the FIA switch is off, this is the same as turning the ignition off at the ignition key, am i right or a just not seeing the wood for the trees.

Cheers

Frank

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Conehead

are you sure your cutting the supply from the alternator?

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PhillB

The large terminals are for the battery feed so that when off the battery is completely disconnected. One of the two smaller spade connectors is for the ignition cutout (i.e. as the ignition switch) to cut the supply to the ecu or coil and stop the engine. The other connector closes rather than opens when the switch is turned off and this is to short the alternator down to earth via the resistor so that the alternator is not damaged when its still turning and hence generating (until the engine stops) but can't charge the battery as its been disconnected. The resistor is used in series with the alternator connection to earth to limit the current as the charge from the alternator is dissipated to earth.

Hope that makes sense?

Phill.

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Cornwallfrank

Cheers Phil,

So in simple terms, as mentioned in another thread, on the switched side, the main + lead on the large terminal is looped to the spade connecter that connects to the resistor/earth when switch is in the off position.?

If correct, any idea what size wire is required for this loop?

The other 2 spade connectors are simply an additional switch in the main ignition between ignition key and ECU. So acts the same as turning off the engine in the normal manner but as the battery lead is now disconnected, the small amount of charge given while engine slows before stopping is effectivly bled away.

Cheers again

Frank

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PhillB

Yes, that's exactly it. Just make sure you loop from the engine side thick +ve not the battery side otherwise it makes a mess when you turn the switch off for the first time. Likewise make sure the correct spade connector pair are used as one closed when turned off and one opens.

Cable size due to the resistor current will be below about 1 amp so it doesn't need to be thick cable.

Cheers,

Phill.

MasterSwitch.jpg

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Nick - Joint North East AO

Copied accross to FAQ as useful info.

Nick

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ianstewartshouse

This was helpful to me as I was wiring up mine at the time. One point of clarification for other numpties like me if you are removing the ignition key barrel

The ignition feed to coil, don't make the mistake I did and try and connect the heavy switched ignition supply from the ignition barrel, this just needs a low amperage switched 12v supply.

As mentioned above, operating the kill switch will open the main feed ( heavy copper bolted connection) close the alternator dump circuit (terminals 1 above) allowing any current from the alternator a path to earth through the resister and open the 12v supply to the coil (terminals 2 above) killing the spark.

If I have said anything wrong feel free to correct me as I'm not an auto electrician but I hope this simple explanation and advice helps

Ian

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mi7rennie

Does anyone have an idea which wire we should use to kill the ignition on our Westy when fitting a FIA switch?

It's a 1.8 MX5 SDV and uses the Mazda ignition key to start, I assume one of the wires that runs to the ignition barrel would be suitable, but which one?

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Cornwallfrank

Just when I thought I had it all worked out I read this in Ian's post

The ignition feed to coil, don't make the mistake I did and try and connect the heavy switched ignition supply from the ignition barrel, this just needs a low amperage switched 12v supply.

This is exactly the route I was going to take, cut the main ignition feed wire at the barrel, extend, and connect to the spade connectors marked "2",

Ian/anyone, why is this a mistake? I'm using an Omex ECU and loom and dont really want to cut into this to find the ECU feed.

Cheers

Frank

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ianstewartshouse

Iade sure I posted this as the main ignition cable is a heavy cable running all the switched circuits on the car. This could see quite a bit of current. If your just taking a loop to The FIA switch to give you switched 12 v it should be fine, I was meaning when you're removing the ignition key barrel.

Ian

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Deanspoors

Can anybody help, to fit a FIA switch to a Megabusa, I'm not sure which wires to use for the "Ignition Switch" + "Ignition Coil". Anyone else fitted one of these to a Megabusa?

 

Thanks, 

Dean

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Deanspoors

Coming back to this again, I'm finally going to tackle the cut off switch. At the moment I have the main starter cable coming from the battery to starter relay and then to starter. I plan to place the cut off switch between battery and starter relay. For the ignition circuit, I plan on using the grey cable which supplies the ignition coils, (I will also be able to use this for my flat shifter). Now the question, the westfield wiring loom is also supplied from the battery, meaning if the cut off switch is activated there will still be power to the rest of the car, lights, etc. should I remove this wire and fit it to the outgoing side of the cut off switch meaning that the cut off switch will cut off everything!?

 

Thanks, 

Dean

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jim_l

Forgive me for resurrecting this and being a bit thick, Which terminal on the (4 way)  ignition switch is part 2 of the cut off supposed to connect to?  

Is switch 2 supposed to interrupt:

a) The main, 35a input into the igntion switch

b) the ignition output to the main circuit, i.e  the output to all of the bits that only work when the ignition is on?

Or - is it just as effective to use part 2 of the switch to interrupt the supply to the fuel pump? 

Cheers,

          Jim

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TableLeg
On 28/09/2015 at 07:35, Deanspoors said:

Now the question, the westfield wiring loom is also supplied from the battery, meaning if the cut off switch is activated there will still be power to the rest of the car, lights, etc. should I remove this wire and fit it to the outgoing side of the cut off switch meaning that the cut off switch will cut off everything!?

What did you do in the end? I am in the same situation and wondering if I should keep the main wiring loom direct to the battery or not.

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Deanspoors
10 hours ago, TableLeg said:

What did you do in the end? I am in the same situation and wondering if I should keep the main wiring loom direct to the battery or not.

Hi TableLeg, I have one positive feed from battery to Cutoff switch, then all feeds are supplied from the other side of the switch, this means the switch will shut off everything as it should be. 

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