I have these fuses coming from the fuse box under the hood. I tested them and they were bad, so I replaced with new. I started my truck up, turned on lights and let her run for a few because I had just put in new O2 sensors. After a few minutes I notice smoking coming from the driver side headlight. I shut everything down real quick and it looks like the bulb melted some of the plastic. The wires that the fuses are on lead to the interior of the truck. What are the fuses for and what could have caused the driver's side build to get super hot and melt the plastic housing?