I have a 2001 Buick Century, my heater cycles between blowing hot and cold air. I have recently flushed my radiator as well as replaced the coolant. My temperature gauge rises to a point that the temperature light comes on, but then the heat starts working and the gauge returns to normal. The hoses are firm, showing no signs of engine overheating. Any help would be appreciated.
You probably have air bubbles in the coolant, which were introduced when you flushed the system. You should bleed the cooling system. The exact procedure for bleeding is different for different engines, so you should look in the shop manual for your model.