the temp sensor has snapped off in the vaporiser, Does anyone know if there is a thermal switch i could use to comple the circuit say at 25 degrees?

Easy enough to replace with the correct thermistor ---- usuallly the temperature characteristics are pretty standardised and they are M4 or M5 thread. Most of the LPG conversion companies carry them.
If the thread in the reducer is beyond repair drill & tap a hole in the return water Tee and screw ir into that.


http://www.autogas-lpg.co.uk/spare-parts/77-temperature-sensor-esgi-system.html

[Edited on 29/9/10 by britishtrident]