What happened...starter?, alternator? belt slip? voltmeter spiked to 0

[H.G.P.]

Rush hour traffic....driver pulls up behind me.....dredded incline...shift to 1st......didn't give enough gas....uh...stall. Tried to start hear fuel pump OK..... but ..... IMMEDIATELY WHEN TRYING TO CRANK the voltmeter spikes down and sounds like the "starter or something" is just "whirrling" away. ????????

AAA Plus, back home in the garage...and immeidately upon first try.....turns over and starts! What gives here?

1. The outer fan pulley is sliding, and I can here it "chime" some when driving. Loose fan belt?

2. Pulley problem?

3. The above causing the alternator to short? Thus voltmemter spikes down to 0. ????

4. Bad starter?

5. Jammed gear?

6. Something else?


Thanks !!!