Hello 3Diesels
It is possible that the bolt was left loose by a previous person working on it. It is possible for it to come loose from vibration.
No, the loose pulley will NOT cause the whine noise in the radio on acceleration.
I can't guess at the price difference in alternators without more data.
If it rotates, replace the pulley and regulator.

__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
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1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

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