If its impossible to restring the switch, then you'll need a two pole pull switch (with neon) rated at 45 amps. There are the following connections inside. Supply +ve, supply -ve, load +ve, load -ve and the other two are green and yellow earth connections. +ve connections will use red or brown wires, -ve ones will be black or blue. Your existing switch will have the same markings, if you wish to replace it. It is vital that all power is shut off before you start, or call a local sparky.
John
July 2009