Hello all, I have a 2004 non-heritage Supercrew, 5.4L 4x4 F-150. I would really like a wiring schematic for the lighting system. I have searched this issue and seems like most issues stem from the Multifunction Switch. Would really like to know what the wire colors are for ground and the low beams at the MFS. Thanks! I apologize for posting this twice, thought this was a better place for this question.

 

No ground at the MFS.

Here is the diagram for the headlamps that you wanted



If you have no low beams but the high beams work, start by checking the fuses for the L&R low beams ( different fuse from the high beams ). This would be the most logical place to start.

Turn the main headlamp switch to the head position, make sure the MFS is the low beam position and check both pins on the back of the fuse ( while installed ) to a know good ground.

If this tests OK, next is to check for power at the bulb connector on each side ( you could have burnt out headlamps too ).

 

Thanks for the info! Will be very useful.

 

Ok, so I have no voltage at the 23 or 25 fuses. Would I be correct to assume it is the CJB? I checked from my battery negative strap to the fuse.

 

After further review, I didn't see that the multifunction switch comes BEFORE the CJB, my bad. Will check that first.

 

CJB Fuses 23 & 25 are after the MFS, when it is in the low position and the main headlamp switch is turned to the head position.

Were you in this state when you were testing ?

The other thing I do not see, but want to confirm; do you have any other modifications like HID retro fit / PnP ?

 

I was in that state (low beams, checking 23 and 25) or should say the lights were in the head position. No mods as in HID or PnP. My lights have always been stock.

 

If both sides of the fuse are dead, that shows the issue is towards the MFS.

Time to pull the cover and check the Red w/ black stripe wire at the MFS, to see if it has + VDC when in the same state ( MFS in low position, headlamp switch to the head position ).

Do you have DRLs ( Daytime Running Lamps ) ?

 

No daytime running lamps. Checked voltage at Red/blk wire, nothing. Checked at the Red/Yellow, bat voltage. I think its safe to say it's my MFS unless you think any differently.

 

Measurements say the MFS is bad as long as the switch as set to the low beam setting during the testing

 

Being able to read the schematic (I was out of practice), I jumped the Red/yellow to the Red/Black at the MFS, and had low beams.

 

the only thing left to make it belt and suspenders is to unplug the MFS, and test with a meter over those pins to confirm it is the MFS.
- Looks like it to me, but just bet to confirm the switch solo is causing the issue.

 

Just an update, it was a combination of loose connections and a bad MFS. I assume the loose connection caused the MFS to go out, so I did my best to clean the female terminals, tighten them and put dielectric grease on the connections as well. Does anyone have a part number for the female terminals/pins?