TritonT80 shower not working?

Ive this shower unit for 10years now whlle i have been in this house.A great shower that has been working until recently.If it was a low pessure issue i would recogine this cos this has happened a few times before and rectified promptly. But at the moment only getting warm water if place the temp setting on very high ie.11/12. Even on full power the water pressure indicator is on green which indicates satisfactory pressure. The only thing abnornal is the power indicator window at top doesn't light up.I dont if this means fuse has gone or not.I tried taking cover panel off to look inside but nothing looks abnormal.Also the switch to turn on shower is outside bathroom and dont know whether there is a fuse inside here aswell.Do i need a qualified elec. to look at this or can i safely do a DIY check on it sort problem. Or is it uneconomical to repair and cheaper to replace?Prefer to keep this shower if i can.