This is going to be familiar... I have an old Williamson Temp-o-matic also. Tonight we noticed that the blower was not coming on. I went down to see if the pilot was lit, it is. It seems to be clicking like when the ignition button is pressed on a grill, but it is already lit... We have turned the thermostat on and off, and could hear the gas valve turning on and off, but then "click, click, click, click" is all that I hear. What could this be? Could it be the safety valve? I don't know. Any help is appreciated.