After cleaning the flame sensor it has worked correctly, but now I am thinking about David’s delima and wondering if it will happen when the weather gets below zero again. It has warmed up, all the way to the low teens and the problem happened in the sub-zero weather.
David, please let us know if you discover anything when it gets super cold again, I will do the same. I have talked to a couple of HVAC guys and they are waiting for the cold to come back to see what happens.
Thanks for all the imput,