NECRO ALERT Alternator or battery?

[bryanl]

The alternator doesn't do squat until the engine is running. So if you are having trouble starting, its likely the battery.

A bad alternator can prevent charging and ruin a battery.

If I didn't have the biggest engine I'd prefer high RC over high CCA since RC appears to correlate better with lifespan.

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[tortillasoup]

Alternator whine (really more of a whistle) from a bad diode does not come from the engine. It comes through the radio as a result of interference due to the bad diode, but it is not audible from the engine compartment.

A bad alternator bearing can cause sounds like belt whine, and does indicate a need for replacement, but a failed bearing wouldn't cause a low charge rate.

https://www.youtube.com/watch?v=hmPUUVwIJUU

Very clearly diode whine and this is heard externally and not just "through the radio". Diode whine through the radio can easily be caused simply by a bad ground (ground loop) and not necessarily a bad alternator.