triton opal 10.5 w ?

Hi my hight setting (2 flame button) isn't working, it will switch itself off and low pressure button lights up, the single flame setting works....do I need a new unit, and if so can I go for ANY triton 10.5 w unit or does it have to be the exact 'OPAL' unit... is the fittings the same for all the models??/ cost is a big issue and also the cost of refitting, any advise would be really greatfull. Thank you