i have a 99F-450 with no low beam. Changed out Mult function switch, Headlight switch and bulbs, High beam works when MFS is pulled back. Fuses are good because when high beam is on i checked with test light, lights up but when low beams are on, no power to fuses. Any help would be nice

 

Isn't there a relay in the headlight circuit? You didn't mention checking it. There is one place to look.

This thread has some other areas to check if the relay is OK.
https://www.ford-trucks.com/forums/1...t-working.html

 

And welcome to FTE!

 

I didn't see a relay, I looked at the manual and didn't see one. Checked both under the hood and under dash. thanks for the reply

 

I'm just guessing, since the 450 is different than the 150 and 250 I have.

I downloaded the owners manual for your year and model, and did not see any mention of a relay, except for daytime running lights. Do you have those? (Fuse 28, DRL relay coil).

Also, the low beams are on two separate fuses, as I'm sure you know. Numbers 9 and 11 in the power distribution box under the hood near the brake master cylinder.

Have you checked them for voltage when you want the low beams on? This may help figure out if the problem is before or after the fuse.

There are some wiring diagrams for the '02 F450 that are linked from this thread:
https://www.ford-trucks.com/forums/1...-location.html

Those diagrams make it look like the headlight fuses are downstream of the multifunction switch.

 

On hight beam the test light lights up but under low beam its dead, thats on both fuses. i blew up my volt meter so i haven't tested voltage. Im thinking between light switch and the fuses. Thank you so much for your help.

 

apparently I've been looking at this all wrong, I don't have high beams. Multi-function switch is in middle position, pull toward driver flash to pass, then push to ward engine high beam ( i don't have high beam indicator on cluster) so i may have the dims but not the brights. As to be something simple , but i can't see it yet.

 

apparently I've been looking at this all wrong, I don't have high beams. Multi-function switch is in middle position, pull toward driver flash to pass, then push to ward engine high beam ( i don't have high beam indicator on cluster) so i may have the dims but not the brights. As to be something simple , but i can't see it yet.

 

Fuse 16 on the inside fuse box? I'm seeing it is a 15 amp fuse for the hi beams.

 

And does the flash to pass work OK? That would be a clue.