Okay do the following:
-Make sure your level of coolant is good
-Make sure there's no air in your cooling system. Bleed it.
-Is your engine taking a long time to warm up? You could have a thermostat stuck open. Replace it. If you never replaced the thermostat I would go ahead and do it now regardless if it's the culprit for your heating problem or not. It is a cheap fix ($5).
-with car idling at normal operating temperature and heat set on high, feel both heater hoses (smaller hoses connected to your heater core inlet and outlet on the firewall); they should both feel very hot. If one is cold or just lukewarm your heater core is probably clogged. Flush it or replace it.
If you've never serviced the cooling system, it is something I would advise you to do as well.
Come back if you need more help, or if everything I mentioned check out ok.
Tuesday, December 2nd, 2008 AT 12:22 PM