I have a pair of Amana 90% efficient gas furnaces model #'s GUC045B30B which were installed in 1990. On one of the furnaces, the blower does not go on half of the time. The electric ignitor ignites, gas is released & the furnace heats up. It then attempts to start the blower but half the time the blower never starts up. It sometimes makes (3) attempts or so & then shuts down. The wheel inside the blower moves easily & is not stuck. Could this problem be caused by a faulty switch or relay? Any help is appreciated. Thank you.