Just yesterday our fan for our heater/ac unit started making noise. It sounds like the bearings are going bad or need to be oiled. I checked the unit and it say that the bearings are sealed. If they need oiling use 20wt. My question is should I just replace the fan or try to repair/ oil it. It is a Borg/Warner that is about 20 years old. 115v, 1ph, 60 Hz with a max 9 amp. Can I use any fan to replace this one? Are the generic? Please help because it is going to be a very hot week. Thanks for any help on the subject.