Hi there. When 4 roof lights are on for a while, fuse gets hot and melts into fuse box. Lights are factory fitted powered from relay. Any idea why this would happen?
See if you can find some loose connections in the wiring.
Heat is a primarily a function of resistance and electrical current. Check the fuse terminals in the fuse panel. Is any corrosion present? Corrosion will add resistance and cause heating. Check the fuse panel terminals for to see if the plating on the terminals is not damaged and the shape of the terminals is correct. Anything to give a poor connection to the fuse should be examined. The higher the amperage fuse, the better the connection to the fuse is required to pass that current without heating. Are you sure the lights are factory, not dealer installed? If dealer installed, then perhaps they put too high of current lights on the same fused circuit. Too much current and you will cause heating. Is there anything else added to the same circuit with the lights that is causing additional current to pass through the fuse? Example: add on fan, add on implement valve/solenoid, etc. There are other things to consider, but I would start with above. A picture would help as well.
Thanks for reply. Fuse panel was damaged, so I replaced section of panel. Lights definately factory fitted. Nothing extra wired in with lights. Problem happened first during hedge cutting season when lights could be on for 7 or 8 hours at a time. Could a higher amp relay be the answer or should I maybe think about fitting LED lights?
A higher amp relay or fuse is asking for more problems , such as burnt wires or a fire.
Larger fuse is a bad idea. Don’t go there! Higher amp relay will not help unless the relay itself is getting hot. As you stated fuse gets hot, the issue is at the fuse area, not the relay. As you mentioned you replaced part of the fuse panel due to damage. Could the crimp where the wiring harness connects to the terminal that actually plugs into the fuse, been damaged? Specifically, if just a few of the strands of wire were broken during panel replacement, then that would cause heating. If the wiring harness was damaged at the crimp, most dealers (at least mine does) have replacement terminals and that is an easy fix. LED lights might reduce your current load. You will have to add up the currents accordingly. Don’t assume just because they are LED, you are going to reduce current though. You also need to consider changes to the light/work-area pattern and color of the lighting, if you switch to different types of lights. What style of fuse and amperage is in your fuse panel that is heating? Some styles tend do better than others in supporting higher sustained amperage like it sounds like you have. If you have “mini” fuses, a potential quick/easy/cheap fix would be to take the 2 terminals/wires out of your fuse panel and connect an in-line maxi-fuse style receptacle/holder to the wires. Use the same amperage fuse as you have today. (example if you have 30 amp fuse today, use a 30 amp maxi-fuse in the in-line receptacle/holder being installed) A maxi fuse will have large blades and provide much more substantial connection to the wiring harness which will not tend to heat.