6000 LE loss of voltage

6000 LE 123k miles 3.1 ltr. Just recently I've noticed that when I was sitting at a stop light, the engine cut out and everything shut off. It looks like the voltage shut off because the radio clock set to 1:00 and all of my preset stations were gone. It started up no problem but I'm think'n maybe there is a problem with the ignition switch shorting out? Have these models been known to have ignition problems? Sometimes when I put the ignition in acc. for the radio and then go back to off, it seems to hang up too. Could this be a good possibility? Any tests I can to on the ignition or any other ideas are appreciated, Thanks.

It hasn't done it in a day or two. I did notice too though, the lights on the dash and radio seem to flicker and dim a bit..........maybe a short in the alt.? It has been replaced already some time ago. What should it be putting out at idle. {volts}

13-15 volts should be plenty.

Looks like it was the alt. Bad diode.