The voltage across the closed blower motor relay contacts should be less than 0.1V.
Post a schematic and we can step you through it.
Do not replace parts by trial and error; sometimes it's just a corroded connection that you can fix with fine sandpaper and sometimes the new parts will immediately burn out because you haven't found the root cause.
BTW, one forum survey had the avg. residential HVAC lifetime to be 23 yrs, with a max of 80.
Last edited by Wuzzat?; 09-26-2012 at 02:13 PM.