Plastic on Fuse Melted but not blown!

[erogerd]

I have a 2003 Hymer motorhome.

When investigating why my nearside dipped beam was not working I found that the plastic on the 10 amp fuse (Correct rating) had started to melt on the side that the power comes into the fuse from the switched supply? The fuse had not blown, but the reason the light had gone out was because the heat generated had not only started to melt the plastic on the fuse but also the plastic around the same side of the fuse holder in the control/fuse box under bonnet of the 2.8 JTD. The exit side of the fuse and wiring to the actual light is not affected (Light still worked). I have checked the plug under the fuse box that supplies the power to the fuses and that appears to be OK. A new fuse box from Fiat is £I40.

I did have a problem with that particular light a couple of years ago when the wiring to the light shorted due to wear on a screw just behind the lamp unit which I repaired and replaced the 10 amp fuse with one from Halfords! and I have had no problem since.

Question is, could the fuse have developed a bad connection which in turn generated the heat or could the problem be in the supply side, fuse box or the wiring from the fuse to the light, if that makes sense? Nothing else is affected, just the fuse that I had originally replaced!

Any advice greatly appreciated.

Roger
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[s130]

You need to investigate what other devices/lights/etc are powered off that particular fused feed are.

You should also check the fuse box sockets where the fuse plugs into are clean and tight.

Fuses overheating are generally due to:

Dirty / oxidised contacts
Long term overloading.

A 10Amp fuse is rated at 10Amps. It should carry this load almost indefinately. Hit the fuse with 50Amps and it will/should blow very quickly. Load this fuse at 15Amps and it will heat up and not blow quickly and could last for hours just overheating and melting itself.

You need to check the actual circuit loading with a current meter.