We had a furnace that was misbehaving. It would intermittently drop out (flame would go out even though the thermostat was commanding it on) and not relight. The problem was intermittent. These are the hardest problems to find as you don't know when they are going to occur.
Chris came in, did a through examination of the furnace, listened to my input and observations, and then we decided to change the gas valve. This fixed the problem and the furnace is now working well.
We were really impressed with Chris' thoroughness, preparedness, and professionalism. We are planning to have Chris back when we are ready to change the furnace and water heater.