Alternator hot/hard to turn

1993 GMC Jimmy, L35 Engine (4.3L). The alternator gets quite hot. I've also noticed that when the car has warmed up, if I stomp on the brake and shift into park, the engine almost stalls, and cycles in speed a few times. I posted this last week about the almost-stalling problem. Anyways, all the sensors seem to check out and be okay, so I started looking for other things.

I took off the serpentine belt and checked all the pulleys. The alternator turns with a lot more resistance than anything else. If I try to turn it by hand (say, by flicking the cooling fan on it with my finger), it stops within a quarter turn. I also get a "whine" sound when accelerating when the engine bay is hot.

Is this consistent with alternator bearing wear? How easy should the alternator be to turn by hand, with the car off and the belt disconnected. My past experience with cars is that normally the magnetic field resistance can be felt as you turn the pulley (several times as you go around), like with an electric motor, but in the case I have here the resistance to spinning is constant.

Anyone have experience with this? I've heard that these alternators run hot anyways. I do know that a hot bearing/shaft will have less clearance.

Oh, as an added thing, I could swear that the alternator makes a scrape- scrape sound when you start the car cold.

Reply to
Conan Ford
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Alternators don't have permanent magnets like electric motors, so you won't feel the resistance.

Sounds like the bearings are on their way out. Time for a new one.

Dave

Reply to
Hairy

Yup - sure sounds like the bearing is toasting. You should be able to spin the alternator with no difficulty.

Reply to
Mike Marlow

Greetings,

Alternators should be able to spin freely. Time to replace yours - and quickly!

Cheers - Jonathan

Reply to
Jonathan

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