Wiring a FIA Cut-Out switch

[tvrolet]

Hi
I'm wiring up a car from scratch and have an FIA-style cut-out switch I want to use, but I've no instructions for it.

Obviously the big terminals cut out the battery, but there are 4 other spade terminals off the back. 2 terminals labelled '1', and 2 labelled '2'. Not tested yet to see if they're double pole or just 2 connections to a single pole though. Now presumably 2 of these are for the low tension side of the coil, but what are the other 2 for?

Also, in searching for a wiring diagram off the 'net, what looks like my switch for sale new comes with the description - Comes with a resistor, which when wired in correctly, prevents damage to your alternator diodes, when the engine is switched off.

So, where does this resistor (that I don't have with the 2nd hand FIA switch) go, and what should it be rated? Except that I already have a ballast resistor (2 actually) on the low tension line to the coil; they came with the [Mallory] coil. Is this what the description of the kill switch is talking about, or other resistors somewhere else on the charging circuit?

And finally...in trawling some other sites for tips to wiring things up I see other mentions of ballast resistors in the circuit. Apart from the ballast resistors I already have at the coil, is there any need for any other resistors in the loom? I've just drawn it up so far with the obvious stuff like fuses, switches and relays...no resistors.

Thanks

WB

[Mikey G]

2 of those connections are normally closed the other 2 normally open.
When the switch is in the on position the 2 that are closed are used to interupt the ignition circuit, so you need to extend your ignition switch wires to these so when you use the cut out it opens the circuit and cuts the car out.
The other 2 that are closed when the switch is off will be open when the switch is on, these are used to protect the alternator when the power is cut. Connect a wire from the starter side of the cut out switch (as the alternator is normally connected direct to the starter) to one of the terminals and there should be a resistor that goes to the other side of that terminal which is then grounded.

I'll try to find a picture..

[MartinDB]

A bit cheesy, but it may help . I think I took the resistor values off the instructions that came with mine, and I'm using a bike engine so I've wired the kill switch where you're wiring your ignition.



Martin.

[tvrolet]

Ah, many thanks all. It becomes clear now. I hadn't worked out that 2 of the contacts were closed when the switch was off.

[jack&mle]

Martin

very interesting, I need to find a resitor because I don't have one fitted on mine.

Do you have to have the resistor?

Cheers

Jack

[MartinDB]

Reading the instructions which I found yesterday, yes as you're connecting a running alternator to earth.



Martin.

[Mikey G]

I found a spare resistor earlier with an RS code on it:-
156-349
3R3 10%

Just incase anybody is looking for a replacement, according to RS components it is discontinued but here is the replacement:-

Bugger, due to RS's web address the formating wont allow the link.....
Here is the part number anyway 206-1287

HTH

Edited by Mikey G on Wednesday 14th June 22:54

[Locoblade]

MartinDB said:

A bit cheesy, but it may help . I think I took the resistor values off the instructions that came with mine, and I'm using a bike engine so I've wired the kill switch where you're wiring your ignition.



Martin.

Maybe less cheesy if you'd given me some credit for drawing it

Jack, yes you do need the resistor (and it needs to be a biggie that will handle high current) because if you throw the switch, you get a big spike down that wire and without the resistor to dissipate it, you're likely to melt / blow something, it would be similar to putting a spanner from your +ve terminal to the chassis rail.

cheers

Chris

Edited by Locoblade on Thursday 15th June 17:58

[mojocvh]

It knackers the vr on genny. Watch how it's mounted to the chassis as they can suffer from contact bounce/burning at high rev/vibration.

[eqben]

Hi guys, I have just wired the switch. I find my resistor getting extremely hot every time I cut off the power, but it works fine if I uncut it. Please help, thanks.

[Mikey G]

eqben said:

Hi guys, I have just wired the switch. I find my resistor getting extremely hot every time I cut off the power, but it works fine if I uncut it. Please help, thanks.

That is normal, the resistor is doing its job and the outcome is normally heat when you dissipate the energy. When the power is on the resistor is not connected so is not being used.

[eqben]

Thanks Mikey, I'll isolate the resistor by it self, so it doesn't burn any wires.

[TVRleigh_BBWR]

Hi Anyone still got this picture, as look like the orignal has been removed.

Also is it ok to connect the starter to the battery or does it have to connect to the switch.

Thanks
Leigh