I have a RUUD furnace that stopped blowing hot air last night. I was thinking that it was the high limit switch gone bad BUT the coil ignites and lights but then goes out again after a minute, so since it actually ignites I ruled out that possibility. If the thermostat setting is on AUTO it just keeps blowing continuously (cold air is coming out). I have to turn the setting to OFF in order to stop the blowing. Any other thoughts?