When you turn on headlight switch, the running lights come on but not the headlights. I have the lights hooked up on a toggle switch and they work fine that way. I have tried changing out the headlight switch itself, but the problem stays the same. Any help would be nice.

Normally this condition is the result of a poor body ground connection. Testing for this can be deceiving. At the static(nothing on) condition, testing can show a good ground. However when a circuit is excited, it has a determined resistance and a set current flow. If the ground connection to this or a branch circuit is loose, corroded, or broken wire. This will allow just enough connection to show as being good, but not good enough to complete the circuit with the required amount of connection when energized.

headlight switch is bad, change the headlight switch itsellf will short out, therefore blowing your fuse. turn signals and break lights are on a different relay, therefore they will still work

maybe one of the light connections is grounding out? check the light holders to make sure there is nothing pinched or worn through on the back of the lights.

buy a new switch or used switch for the vehical other wise hook up a toggle switch to a power for headlights and use the switch for other lights if you wanna keep it rigged but i would just replace the switch hope this helps you =check fuses=

This is just an idea, I may be wrong but any input is helpful, right? I would think that the switch that controls the plow lights is designed to alternate between the circuits for the truck light and the plow light. If the trucks headlight switch is turned on then the circuit is closed and turnes on the light. When the plow light switch is turned on it may cut the hot side of the circuit going to the headlight and engage the hot wire to the plow light. The headlight and plow light may share a common ground. If they don't share a common ground then the plow switch may cut the ground wire opening the circuit. If you can't find a solution you can always wire the plow lights directly to the battery with the same switch or a new toggle switch and then turn on the parking lights only on the truck. On most GM cars and trucks there is a space in the fuse pannel that is for a power accesory. It is basically a fuse slot that is empty labeled ACC. This is a 12V hot power source and you would run the positive wire here then ground the neg to the chassis. This way if you forget to shut off the toggle it will cut the hot when the key is shut off. When running the wire it is near the hood release able and you may be able to run the wire thru there and not drill a new hole. I've done this for neon lights under cars as well as stereo systems requiring an amplifier. If you drill a new hole even though its under the hood I would put a little blue RTV silicone over the new hole to prevent moisture from getting past the fire wall or road salt.

SOUND LIKE FAULTY DRL HEAD LIGHT RELAY.CHECK HEAD LIGHT RELAYS YOU HAVE RELAY STAYING CLOSE NOT OPEN TO TURN OFF CONTROL CIRCUIT TO HEAD LIGHTS.

The relay has nothing to do with the tail lights, but replacing the switch sounds like a good idea. There's a nut holding it in place, see http://www.skandix.de/en/spare-parts/electrics/switches/switch-headlight/1027524/ to get an idea of the construction. And the price. This is not worth fiddling about unreliable workarounds...
In addition, if fuses 15 and/or 16 burn frequently there might be a problem with the tail light cabling.

Good luck
Ingo

Check all your fuses, and the Headlight bulbs

check your ground on the radio......... the feed from the lights will test as a ground and the radio will use this as a circuit and turn on the lights. been there done that what a nightmare

Sounds like your headlight switch has failed. I have a 99 Audi A4, and when mine died, it was the same exact problem (it's a known problem area for the Audis). Given that your car is behaving the same way, I'd look into a new headlight switch as a solution. The toggle-for-highbeams feature is wired separate from the normal headlight wiring and is a simpler contact setup. The contacts and wiring and switching for the low and running high beams is more prone to failure. You should be able to find a switch assembly at a salvage yard for less than $15 and can probably change it yourself in a half hour to an hour.