Melted fuse/holder

[F14CRAZY]

While on the road last week my Catz XLO driving lights, wired and installed by Drake, quit. I got around to investigating the issue today.

Seems this was the issue:



They're wired to the battery with a 15 amp ATC fuse straight from the battery, to a relay in the relay box. Also wired up to turn off when the high beam or flash to pass button is pressed.

I looked over all the wiring and connections and didn't find any bad insulation or shorts or any other issues. I replaced the fuse holder (and fuse) and they work fine again. Relay is working fine. Left them on for a few minutes and felt the wiring...not getting hot. Everything seems to be back to normal but why would the fuse and holder melt like this? I thought fuses were supposed to blow when there's an issue  :falldown:

[Scott_]

Looks to me like like either:
1. The fuse holder wasn't holding the fuse tightly enough, or
2. The female receptacle portion of the fuse holder had a bad/improper crimp connection of the wire conductor.

Either way a bad connection created the heat to melt the fuse.

[kioolt]

Continuing on what Scott said.  It looks like either the fuse holder wasn't holding the fuse tightly enough or maybe even the fuse holder factory crimps to the fuse clips were not done correctly.  A fuse is designed to blow at a given current rate after a given time period.  In your case it doesn't appear that the current rating of the fuse was exceeded.  I would suspect a bad fuse holder.

[jensk]

On Honda early CB's from the seveties it is a common error that the engine suddenly dies with no aparent reason. There is no power at all like if the battery is disconnected. All fuses look good.
 
This happened to me once on the way back form a trip to the other part of Denmark. Just passed the toll station on the Storebælt bridge and the engine died. After ½ hour of searching for the reason i had to call for assistance to get transport for me and the bike the last 100 kms home.

The error is caused by oxidization on the contact surfaces of the main fuse and fuseholder. The oxidizatiion acts like a resistance  and the fuseholder gets warm when current runs. In the end the fuseholder gets so hot that the solder on the back of the fuseholder melts and in the end the wire disconnects from the soldering joint on the back of the fuseholder - and the engine dies.

When home I cleaned all the fuses and fuseholders soldered the wire back on the fuse holder and all where back to normal..

[Bfbob]

Seconding the previous posts.  A resistive connection generates heat at the point of whatever conductivity there is, sometimes to the point of actually making an arc.  The telltale in your case is that there is very localized melting/charring, not the whole fuse holder and wire.  This is a well enough known phenomenon that the National Electric Code now requires Arc Fault detecting circuit breakers in new homes - at present only in bedrooms.

It's easy to demonstrate the phenomenon with house current. (Not suggesting you DO this!  It's dangerous!)  Rig up a 100 watt incandescent bulb with one of the wires cut in two. Touch the cut ends together and it completes the circuit, lighting the bulb. Brush the cut ends together lightly, and you'll strike an arc, just like an arc welder.  You know how hot that is!  But, since the current is passing through the bulb, it never exceeds about 1 Amp, and so never trips a conventional 15 or 20 Amp breaker.   An Arc Fault breaker detects the high frequency fluctuations due to the arc and shuts it off.

Just replace the fuse holder and fuse, and this time put a little dielectric grease on the connectors--even WD40.  It might get wet. :hehehe