On a 93 f350 460 5spd 4x4 reg cab. No low beams when running or not. I used a test light at the bulb connector to check for power only sporadic when I pull the headlight switch in\out. I do have power for low beams all the time at the switch and at the red\black wire out the multi. Also tried a different multi switch and main headlight switch is newer, I tested across H and B1( going from memory) continuity all the time.
I seems going from the multi to the light bulb socket is a "bad" connection, question is where does the power wire go thru the firewall? I took a look at that large plug under the brake master cylinder it has a red\black wire that is a couple gauge larger than out of the multi plus no continuity from the outside plug side to bulb socket so probably not it.

Also: High beams work all the time.

 

That big main connector on the firewall is the interface between everything inside the cab and everything outside.

 

Is that the C202 plug? If it is I can not find good diagrams via google....

 

I had both low beams go out on me at the same time in a 94 and it just turned out to be they were bad bulbs. High beams worked still. Put the new bulbs in and good to go. I'd like to assume you already tried new bulbs though.

 

I'm not sure of the actual part number. I believe the user subford on here is the wiring schematic guy.

 

Turns out that this one has trailer tow pkg from factory and low passes thru that relay, all the diagrams I found do not mention this. I have another truck like this same spec a 92 but crew that does not have factory trailer tow pkg (no relay in power box) it is wired direct. Replaced the relay in the 93 (built late 92) and lows work.
Real tricky...

 

Interesting. Glad to see you fixed the issue though!

 

Wow what are the odds of that! I bet it's like more than a trillion to one or something.You really have to question if you lost one a month or at least a few weeks earlier and just didn't realize it,rather than both actually blew at the same time,leaving you in the dark.It's a wild story though so I'd stick to it.

 

Possible but with out of state tags and expired inspection stickers I was an easy target for the Phoenix police.(and worked nights) One ticket was for "waste of finite resources"(gas), and littering when I responded "probably threw it out the window" when asked about my last cigarette(not the one I was smoking at the time).

Judge threw them both out. Told me to be a good boy haha