The car warms up correctly however cold air comes out of the inside heater. I have changed the thermosat and watched it work when it heats the engine then backs off. It does seem to work alittle at times but doesn't come out hot at all. All suggestions are welcomed.

 

Welcome, Do both heater hoses get hot? Does car have Dual control a/c? If so, does either side get heat?

 

I'll check on the hoses, and yes does have duel controls and both are cold.

 

See if ACM codes are stored, FAQ section will decribe how to get them if you don't no how.

 

I did check the hoses one is hot and the other cold. So does this mean the heater core is clogged or a valve not opening?

 

Good chance it is. Disconnect heater hoses remember which is which, take garden hose press it to the cold hose side of heater core and try to force out the gunk thats blocking it, if gunk comes out after a few minutes and water is flowing strong. Turn hose towards heater hose to clear gunk that may be in pipe going to core. Then flush cooling system. If no gunk comes out you need heater core, and you will still need to flush cooling system either way.

 

I just had the sameproblem in late October/ 08. Replaced the heater core. Heater core got clogged due to wrong anti-freeze being used in the car. The shop that replaced the water pump told me I didn't need that GM anti-freeze. They were wrong.

Don't know if you have the same situation.