423 Quick water heater difficulties

I am beginning to experience problems with my Quick water heater such as the heating solenoid, when linked to shore power, has stopped working. The heater itself has started to leak small amounts of water. As the heater is encased in a metal box which I'm finding difficult to get into I was wondering if any other owner was experiencing the same problems. The boat is 8 years old. I am wondering if the safety valve is releasing water or I have corrosion. My understanding is that it has never been bled over the winter period nor has the annoid been changed in the heater..