anybody have an idea on how to remove under dash fuse box ? my dash illum. lights won't come on. Light switch wire brown feeding fuse #18 has 15 vdc going out of light switch, but is not feeding fuse #18. the brown wire does ohm out good from switch to either side of fuse #18. pulling my hair out, and I'm electrically inclined.When I bypass #18 fuse ,and jump brown wire to drk. blue w/white stripe I do get dash lights. H E L P !!!!!!!!!!!!!!

 

bit confused on this one.

you say you have 0 ohms when you check from the pin #4 on the main headlamp switch to one side of fuse position #18, but fuse #18 does not have power ?

You say when you pull Fuse #18, and put a jumper in its place, it it works, have you tried a new fuse.
If a piece of wire works, and your fuse does not, sounds like you might have a bad fuse.

If you have parking lamps working ( on the exterior of the truck ) you know from Fuse #7 to splice S224 after the switch is working correctly.
S224 is where the exterior parking lamps separates from the instrument illumination, which would narrow the problem to between Splice S224 and Fuse #18.

 

thanks for reply. If I jump wires out at light switch #4 brown to#1 d. blue w/white, I do get ill. lights. The brown wire from switch term. #4 to #18 fuse socket - now I have 14 vdc.The other side is a d. blue w /white stripe wire feeding back to light switch term. #1, to power ill. light circuit. The d. blue w/white stripe wire does not ohm out between #18 fuse socket and light switch, and I lose my 14 vdc. so now I narrowed problem down from fuse#18 C242 and C245, which I believe this means I need to access the rear of the fuse box to find my wire issue

 

If you bypass the fuse F18 you get lights, did you replace the fuse ? Don't see a note of this anywhere.

Does this mean when you have the main headlamp switch in park or headlamp position, one side the Fuse #18 has power at it ?
If so, what does the other side show in the fuse holder ?


Think you could have damaged the connector or the switch from this ?
https://www.f150online.com/forums/el...er-lights.html


Might want to see if you broke the connector in this area. You would need to go back further in the instrument illumination wire, and test again. Else test with a new switch.
Have not seen a problem at the rear of the fuse panel, unless it is overloaded and melted something. I would start an inspection of the switch connector.

 

Not sure whats the problem is, but all my ill. light issues started when I removed the headlight switch. I never disassembled the gutts of switch, but when I removed the ****, I busted part of the **** retainer which may have dislodged the inner contacts? So I'll locate a new-used switch, and try that route. Thanks for help

 

Hayes manual sucks for elect.wire schematics. Found fuse #23 was bad. I replaced fuse now have illum. lights.