RedRaptor

So this might be a long one but, the previous owner of my truck put aftermarket headlight housings and has put LED bulbs in, as well as the fog lamps, i have the 9004 bulbs and when i keep it on low beam the headlights don't work, but when i put them on high the drivers side headlight comes on, the passenger side doesn't work at all, although the blinkers in both work perfectly, I was heading to school when i realized the problem and stopped at advanced auto for a quick replacement and i ended up having to buy a HID bulb instead of LED but it didn't work either so if any of you guys have and theories or solutions, thank you. oh also I would kinda like some quick help since i have night classes lol

AlpineRAM

The problem might be that the trucks used a ground switched system in stock form- any LED will only emit light if it gets current with the correct polarity.
I would start with a multi meter checking what goes on at the plug for each bulb-something like:

Left: Off= left-center 0V, Left-right 0V, center right 0V
low beam left-center -12V, left right -12v, center-right 0V
high beam ............
Play this for both headlights and report what you find- since there are unknown modifications in there it is hard to determine how to get your lights back without more info.

RedRaptor

So we ended up testing the connections with a meter and it was all perfect so we were then even more unsure of what it was so we check the fuses and the stock 15W fuses were both out so I replaced them with a 30w until i can figure something else out, i do run LEDs which i think take around 20-30w so they burnt through the stock 15w fuses instantly, but i put the 30w fuses in and drove home one the LEDs (i think) doesnt work in general so i through a standard bulb in for now. I would like to keep the LEDs and i am getting custom housings for RGB bulbs which will take up around 36w what should i do if i would like to keep them? just run bigger fuses or acutally do some wiring?

AlpineRAM

A fuse is marked in Amperes, not Watts.

Watts = Volts x Amperes

A 15A fuse and 12V equals 180 Watts. If you blow this fuse immediately there is something dead wrong.

Fuses are the things that burn in a controlled environment so that the rest of the wiring does not burn uncontrollably.. burning your truck to the ground..

Never go bigger than stock on a fuse unless you re-did all the wiring in this circuit! Extremely dangerous to life, health and property!

The stock headlights are 50-55W per filament, the stock fuse will not blow at 100 Watts for both lights.

Something else that's fishy- you tested your connections with a meter and all was OK even though the fuses were burnt? What exactly did you measure?