I have a Raypac RP2100 heater. I was getting an error code of INT (the display is hard to read), the service light then flashes and heater will not start. I had a guy come out and said the high tension wire was loose. It then worked. About a week later it did the same thing and would not come on. I had the guy come out again and it started right up for him. The display shows the CFH and SPK codes, temperature, as it should. What is wrong, any ideas for this random problem?