Hi, if the wires are burnt it is most likely a poor connection, bad connections = heat (& fire) and as this connection is on the thermostat the heat is travelling into the thermostat and it is operating.
I advise you not to use your shower until you have these wires replaced. Ask any fireman and he/she will be only too happy to tell you of the horrors of overheating wiring connections and house fires. Triton normally sell replacement wires as spares and as always these should be installed by some-one competant at electrics.
I hope this helps,
Paul M
January 2009