Have had trouble off and on for 10 years. One problem was getting the pilot lit. On 2 occasions we shut the system down for extended periods and spiders moved in & blocked the orifice. I removed the orifice & cleared it and was successful in getting it going again. The temperature regulation has been a tough problem also. The temp does not fluctuate with even water pressure if I turn on the hot water faucet first and slowly turn on the cold to get a comfortable temp. But heaven help anyone in the house that uses the water in another room when I'm taking a shower! Recently my problem is that I cannot light the pilot. How can I tell if the overheat sensor is causing this? Would de-scaling help too?