Not everyone lives that far north. I like the extra light that this mod does. Down here we usually have thick fog and no I don't drive in the fog with brights on.

 

I see alot of the replies question why do you want this etc. Hey it's your truck and to be honest I may do it someday.

Oh well here it goes, I referrenced the 2009 F150 wiring diagrams to come up with this solution. The 2004-2008 wiring diagrams are totally different.

For the 09's Ford has installed a solid state controller / fuse panel called the SJB, Smart Junction Box:
FORD believes the SJB increases reliability and lowers manufacturing costs.

the SJB / fuse panel is located behind the right hand (passenger side) kick panel
the bad news: several controls (relays) are now solid state, so altering them is not a real option. This includes the fog light "relay" the wiring diagram sez "not serviceable", so if it quits some day it sounds expensive, so a work around is in order.

So how I would keep the factory fog lights on with the High Beams?
I would make the fog lights operate off the running lights

C1023 is the connector to the drivers side running light
pin #2 (18 gauge wire, the center of 3 pins) of C1023 is the +12v going to the light

I would tap the wire from pin #2 to control a new fog light relay / rated for >20 amp & >12VDC, the extra load of the relay coil should be OK, the circuit for the running lights is fed from F22 (15amp).

Fuse F21 (15 amp) feeds the fog lights, the owners manual page 316 tells us the fuse panel (SJB) is located under the right-hand side of the instrument panel.
I would remove F21, tap into the "hot side" and install a 15 amp inline fuse then run the power to the relay contacts. Pick up the power coming out of the relay contacts and go to the connectors to the fog lights, C152 & C162.

(Or better yet, so you don't need to find a way to the engine compartment from the cab, remove F21 and tap off the battery with a 15amp fuse to feed the circuit)

@ C152 & C162 I would remove & insulate pin B (18 gauge wire, the +, not the ground) and install the new wiring from the new relay. Or better yet you could buy the 2 connectors from Ford, Pin A is ground and Pin B would be the +12v from your relay.
Then to return to OEM functionality, reinstall F21 and plug in the original C152 & C162.

Results should be the fog lights would be on whenever the running lights are on.

 

Man.....am i on an "F-150 FORUM" or an F-150 RANT!! OMG!! This forum is probably hands down the best place to seek help on mods and everything else you desire to do with our f-150, But lately it also seems to also be the place to be take it upon yourself to critisize guys on whatever it is they happen to ask because you personally dont agree or like what it is they want to do with their truck. I agree if you dont have any input or knowledge to add or answer to the question asked then move on to something else. Everyone on this forum already has or had a father we dont need another one! Thanks to all that continue to help out, even if the question was asked 100 times before!!