2000 Pontiac Grand Prix

Welcome to the forum, do you live in an extremely cold area, if so, you may need to use a block heater. Does the engine ever reach normal operating temp? Do both heater hoses get hot? My next step is to check the directional doors, see if they are operating like they should?

Yes, I live in Minnesota. I replaced the thermostat, and i still have the same problem. It feels like both hoses are getting hot, and my temp is fine. I have good heat if I shut it off for a minute and turn it on high, It works great for 10 seconds then gets cooler and cooler. I'll look into the directional doors... Do you think putting a piece of cardboard in front of my radiator would work??? Thanks for all your help!!!

I have blocked off radiator on some of my old trucks, to get the heater to work better. You really need to be careful doing that, don't let the engine overheat!!

If the problem is the directional doors, blocking the radiator won't help.

How do I get into the directional doors?

You'll have to get up under the dash.