Condenser fan motor bearings are bad on my home ac unit how can I tell?

my home ac unit is blowing warm so had a company come out and look at it. they said the condenser fan motor bearings were shot. I declined replacement but after he left I went on the roof to check it myself but did not notice any looseness or grinding when i spun the blades. How would tech know? would this cause it to blow warm it is a heat pump rooftop unit.