A short while ago I had a rapid on-off cycling of my Intertherm RSH-MS-065 fuel oil furnace I suspected was the T-Stat. Anyhow, I replaced said T-stat, as I kinda wanted to upgrade the appearance anyhow, and the furnace seemed to work OK the 1st couple times. Should be noted that I am in Florida so it does not get used very often or for long periods of time. Anyhow 2 days ago I turned it on to remove the night chill from house and although furnace light and ran fine I could hear the relay inside the flame control box clicking, oddly the furnace stayed lite and fan ran . Today I tried to run the furnace and it would run for a short bit and cycle on and off. I think it is control unit because it does not just shut off the burner, sometimes it cycles the blower fan and everything like you are killing the power to the entire unit. If it was the flame detection part of the system it would still run the blower fan (like in the cool down/purge) right? I jumped across the T-Stat wires and still did it, that removes the T-Stat from the list of possible issues. Anyhow it is a White&Rogers TYPE 668-410 control box and I found one place on the web and it looks like it has been preceded by a 668-415 box. I saw there are other types of burner controls that appear to be solid state, can I upgrade my control unit?