Furnace help

Milemaker you are correct mine also starts with a signal from the thermostat. This starts the fan, the sail switch then closes to power the ignition board. At shut down the fan runs a cool down cycle. When I took the RV in to have the safety check done the tech told me that the furnace lit but the fan didn't come on and offered to pull it for a fee of $150.00-$300.00. after getting a set of prints thanks to Tiger4x4RV I too thought it odd It would light but after pulling the unit I feel like the sail switch most likely was stuck closed. I pulled all the switches and found the fan switch was sticky as well but working. I tested them over a light bulb. this led me get all new switches. The main problem was the mechanical Time delay relay. one of the coil wires appeared to have come in contact with the metal case causing a short circuit and burnt the wire into. This and a stuck sail switch allowed the furnace to ignite and the fan remain off. I bought two relays,fan and limit switches. So now I have a complete set of spares I hope I wont have to use.