What are alternator bearings? Why, when the mechanic said the alternator was ok, but the bearings were bad, did he replace the alternator as well as the bearings? The car is a Nissan Sentra with 150,000 miles on it
Click on this web address to see a drawing of alternator with its bearings: tpub.com/content/construction/14273/css/14273_47.htm. The bad bearings made the whole alternator bad.
In the old days it used to be commonplace and cheaper to disassemble an alternator and replace the worn parts like bearings, brushes, and voltage regulator. Now though, they are more difficult to take apart and labor costs are higher, so it is cheaper to just replace than to rebuild it. The bearings are what the armature rides on so is a main component even though electrical current is still being generated.
Usually, a Japanese alternator should be left in for 240,000 miles at least. However; if you had to pay the labor for changing the bearings, it could have been almost as expensive. Sometimes, you want to keep the mechanic happy. Pay this way or pay that way, but you now have that rebuilt alternator. They don’t ALL go 240,000.
Where did you come up with 240k for a Japanese alternator? The Nissan Sentra we had went through 3 in 120k; all electrical failures, not bearings.
The alternator on my Nissan Altima went at 82,000. I think you got lucky.