Do you hear the gas valve click after the fan has run about 30 seconds? If you don't, it could be the fan sail switch
If the fan sail switch is stuck in the off position or inoperative the gas valve will not open. Insect nests will cause that to happen. Obstructions in either the intake or exhaust area will affect the air flow which also affects the sail switch. Wasps, mud daubers, and spiders love to nest in these areas.
Good luck.
Bill
If the fan sail switch is stuck in the off position or inoperative the gas valve will not open. Insect nests will cause that to happen. Obstructions in either the intake or exhaust area will affect the air flow which also affects the sail switch. Wasps, mud daubers, and spiders love to nest in these areas.
Good luck.
Bill