I cleaned the SENSOR.and noticed there is no igniton lignt or spark present ,when starting the furnace !

Only the gas exhaust blower running ! Alas I noticed there is a pilotlight tube running toward the Gas valve!? And no Pilot ligt present !(Is Gas valve bad?? )

This Tempstar high efficience furnace is 18 years old !

Ignitor. Or defective spark circuit or bad end switch on exhaust blower or bad perssure switch.To start with