FIA Kill switch - wiring info

[fordy]

Im talking about the one with the 2 extra connections on the back and comes with a large 3.3ohm resistor - anyone know what these wire to???

thanks

Chris

[Richard M Green]

My understanding is that the additional two pairs of poles on the FIA switch act in opposing senses, thereby serving two purposes:

1). The pair which 'make' when the main battery switch poles 'break', connect from the alternator +ve output (i.e. +12V permanent live), via the large wirewound resistor, to earth. This provides a 'dump load' which takes the alternator output and dumps it in a controlled fashion to earth/ground/chassis during the period between the master switch being turned OFF and the engine, and hence alternator, ceasing to turn. This protects the regulator circuitry within the alternator, and in so doing prevents the alternator producing a voltage spike which could destroy any other electronic circuitry in the car.

2). The pair which 'make' when the main battery switch poles 'make' are used to provide the positive feed to the coil (and/or ECU if applicable). Thus when the master switch is turned OFF the power source to the coil is removed and the engine cannot 'run on' using any residual power being produced by the alternator.

Hope that all makes sense.

Regards all

Richard

[fordy]

THats greats and make sense - i didnt realise one was a make and one was a break - ta very much.