Are you saying that it only ever blows hot?
Both sides of your dual temperature control? Are you able to adjust it to 60 overall? And it still blows hot?
Can you verify if the air conditioning compressor is turning on when you do this?
It can be a heater control valve problem. The dual climate control heater control valve did have some problems in the 2000 model. Most times when this fails, though, the temperature shows a difference from the left side to the right side.
Whether it is temperature blend door issues, a heater control valve issue, or a control head issue - the best thing to do is get a diagnostic tool that can interface with the system and check out the components. Nothing in this system is cheap, so get it right the first time.