My 2003, 50,000, Gran Prix has been allowing
both my day running headlights & Heater Blower to
go off and on at will ?
No fuses appear to be shot, has a new battery.
Can't seem to locate anyone else w/this same problem?
A Voltage Regulator?? A faulty ignition switch??

I need to know the Why?, the Where?? and the How?? I await all responses, thank you!

Get a battery/alternator test at autozone. Are these the only devices that are losing power? What about radio or interior lights? It could be a poor connection. Or as you say, ignition switch.

Start with the easy things. I would try putting a voltmeter across the battery terminals while the problem is occuring. It should not be changing much, if it is alternator is suspect.

Sounds like a bad ignition switch; here's a write up: Ignition Switch Instructions (With Pictures)