A good friend of mine has a 2004 F150 FX off road , has 180k miles. The last time he plowed with it the high beams went out. The low beams still work. Without the plow on the highbeams are still out. He got a new fuse at napa and changed it. As soon he put the new fuse in it last a milli secound before blowing. SO. I assume this is a shot or ground somewhere ?
Any input on what to look for or check would be much appreasted.

 

check the headlight wiring harness for damage. but if the fuse blows right after put in with the high beams on that could very well be an issue with ground connection

 

Yes, there is a short to ground somewhere.

 

Try unplugging one headlight at a time, then try the lights. May help you narrow it down.