Hmmm. My 04 and 16 you can turn on the fog lamps while the parking lamps are on via the normal switch..... coming on with only the headlights defeats the purpose of fog lamps.
Mine works the same way... fogs come on with the switch. I'm guessing you didn't read my original post carefully, or maybe I didn't explain myself clearly, but what I'm trying to do is get my fogs to stay on even with high beams. They are already on with parking lights and low beams, but I want them on all the time. They help light up the area directly in front of my Expedition and out to the sides where the high beams don't reach. My thought process in tying them into the parking lights is that the parking lights are on all the time that the headlights are on (including when the high beams are on), therefore my goal would be accomplished.
On vehicles with separate bulbs for highs and lows, this is not as much of an issue. My 2007 MKZ has separate bulbs for highs and lows, and when I switch to high beam, the lows stay on as well, lighting up the road nicely close up and at a distance. But my Expedition has one bulb for both highs and lows, so when I switch to highs, the lows go off and leave me wishing for more light close up and out to the sides.