I have a 7 year old weil mclain heater which suddenly started to run continiously. I have isolated the entire thermostatic wiring system from the boiler, but when I turn the power back on, it fires up. Bad relay? Please advise. Thanks, I don't really have the cash for outside service. Thanks for any help I may get Let me repeat. I have disconnected the entire thermostat circuit fron the heater. The problem lies within the heater electronics. The thermostat leads coming fron the heater are "open" Still runs continiously.

1 aw not a heating pro but, ir could be the thermostat itself checking wiring is good but it won't matter if the actual thermostat no longer works