99 f350 v10 (05 psd on thw way). About 2 months ago one of my headlights started dimming out. The high beams were stuck on and I had to diconnect the 4 fogs that were wired into the highbeams. They were IPF's and I installed them like the instructions said. They worked good for 3 years. I was a little confused, especially when it fixed itself a week later. Everything was cool for a month and I got in my truck after work and no headlights at all. The high beam icon is "on". taillights and running lights work fine. So I stopped at shcucks and looked at all fuses and they were all good. It was a Canadian truck with DRL that I took the fuse off at first purchase. I decided to replace the DRL fuse to see if that worked. With it in and the highbeams on, some horrible sound emitted from under the dash. Man I thought my truck dyin'! i took the DRL fuse out and drove home with 2 fog lights that I plugged back in . Any body know what this could be?

 

Just a WAG - could the extra current from your 4 extra fog lights have melted something (switch or relay) in the path for the headlights? I think when you add lots of extra light like that you're supposed to run them on a separate relay.

Duncan