[Shotimes] dying alternator?

[van Oss]

Sometimes when I'm sitting at a traffic light, the engine stumbles, even 
stalls, and I notice the voltmeter needle dives during the stumble.

In the past when I've had stumbling at idle, it was a sticky IAC valve. 
Could be that again.

If the volts take a dive during an idle stumble, is that just because revs 
get so low?  In which case I maybe should look more at the IAC than the 
alternator?

I guess I could just clean the IAC and get Sears to test the alternator for 
free.  Any suggestions welcome.

VO