Heater not working only blows cold air, blew warm air for about 10min then cold after that and never worked again. Need help, any advice?

 

your heater core is out
pain in the butt to change. you have to take dash out. mine is broken also

 

double post oops

 

I have a 2000 millenia and I had the same problem. I downloaded the repair manual for a 96 millenia, which is not exactly like the 2000 but here the site "http://rapidshare.com/files/51248650/Millenia-1996.rar". We took the radio out to see what we could find and at the same time my friend was reading over some things I had printed off. Come to find out it was the c/c computer needed to be reset. In order to do that you can find that on Pages U22-U26 of the manual. It was either that or it might have been where we took the negitive cable off the battery for about 2 minutes either way I have heat now without taking the dash out. If you can't download the manual let me know and I look at it again and explain it to you. Good Luck!