The blue flame would short cycle and turn off and kick back on every few seconds. The problem ended up being the high limit sensor, and the heat exchanger was getting too hot so the safety mechanism would shut the flame off and then it would kick back on and get too hot again too fast and kick back off. so I ended up reducing the amount of gas turning down that blue flame and the unit would stay on much longer sheathing the garage for its purpose until it reached the set temperature.