Welcome to TTORA!
So if your air stopped 5 years ago, what are you trying to ask? Why it stopped? Why your Taco only runs "o.k."? For the air to not work, there are bunch of things that could happen...
1) bad compressor
2) leak in the line to allow the freon to escape
3) bad dryer
4) slipping belt that powers the compressor
5) bad fan motor
6) bad controller
you need to tell us more about what you hear or not hear or not see operating. Plus this type of question is more towards the NEWBIE Tech thread or like everyone here will first mention...
Check out the Search Button and Newbie Tech thread to see if your question has been asked and answered in the past.