My headlights quit one night and I can activate my high beams with the flasher. I replaced the 200.00 MFS switch and still no luck. All fuses and relays seems okay and I am at a loss. Also, the running lights are now out.

Any clues?

 

Hey Corky,
Give this poor boy a break and tell what year truck you have.
Does the parking lights work?
Does the turn signals work?
Does the 4 way flash work?
All rear and stop lights work?
Back-up lights?
Does the lights flash when all the doors are locked at exit?
There are a bunch of fuses and relays involved.
It greatly helps to know what does and does not work when tracing circuit problems.
Could be as simple as a open ground.

 

try swapping fuse for its neighbor of the same power rating, sometimes a blown fuse looks perfectly new

 

What fuses are you checking ?

There are 4 fuses in total on a '97-03 F-150 for the headlamps. Depending on the year, is depending on which position.

Power distribution/Battery Junction box ( under hood )
1997 is Fuse #8 30A
2001 is Fuse #3 30A

This fuse feeds the Main Headlamp switch, to supply power to the MFS, if in the main headlamp position.
This is to the MFS, and then to 1 or a set of fuses depending if the MFS is in the low or high beam position

The High beam position ( Central Junction Box / Pass compartment )
1997 is Fuse #16 20 A
2001 is Fuse # 16 20 A

The Low beam position ( Central Junction Box / Pass compartment )
1997 is Fuses # 26 & 28, each 10A
2001 is Fuses # 26 & 28, each 10A

The only relay that would be in the lighting system is for the DRLs. Without DRL, there is no relay for the headlamps. What relay did you check, and what was the test procedure that you used ? I take it by your testing of relays, that you have DRLs

In the 2001 the BJB Fuse # 3 30A also feeds the Flash to pass function, which bypasses the main headlamp switch all together.
You said this works, so we know the 30 A fuse ( MY Dependant ) and the high beam fuse is good by you post.

I would take a shot in the dark ( which needs to be verified ) that you are having a problem with the main headlamp switch itself ( no headlamps other then FTP, and no parking lamps ).

Quick test :
1. Pull the Central Junction Box fuses # 26 & # 28
2. Turn the main headlamp switch to the headlamp position
3. Pull back on the MFS, to verify you are in the low beam position ( might just indicate by a FTP ).
4. Meter both sides of the CJB Fuses # 26 & # 28 and you should have + 12V DC.

If not, power is not making it from the 30A fuse through the main headlamp switch, the MFS, and to the low beam fuses.

While this could be another bad MFS or a problem with the connectors, it shows at least one step in the problem diagnoses steps.

The confirm would be to remove the steering wheel column ( with the same test setup as above in steps 1 to 3 ) and meter for power on the Red w/ Yellow wire ( marked as pin 507 for some reason in the '01 diagram ) for power. This is on the side heading towards the Fuses # 26 & # 28.

 

So, Corktex.... did you ever find the source of the problem?

The reason I'm asking is that this same problem happened to me last year with my '98... scared hell out of me because it was late at night, good distance from home. I figured out what the problem was, but forgot how I did it - I think a switch wasn't fully engaged (yeah, it sounds stupid, but that's how I fixed it!). If you still haven't resolved this, let us know.