edog1973
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1961 Traveleze
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Post by edog1973 on Aug 4, 2014 9:39:56 GMT -8
While we were camping this weekend in the Red Dale I smelled something burning and tracked it down to a melted 12 volt fuse!!! This circuit powers the vent hood over the stove which has a fan and a 40 watt light bulb. We had both turned on at the time which draws a little over 5 amps between the two. The fuse that melted was a 10 amp fuse. You can see from the picture that the plastic melted but the metal fuse was still intact. After finding this I installed a new fuse and watched it for an hour or so with the fan and light on. The new fuse did not get hot at all. Could this have simply been a cheap fuse? What else could have caused this?  |
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Post by danrhodes on Aug 4, 2014 15:02:04 GMT -8
Fuses can get reasonably hot before losing continuity. Your 40W lamp is drawing over 3A alone, so there's a good chance that your load was greater than the 5A you think it was, but not quite the 10A the fuse was rated for...
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John Palmer
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Hi, From a vintage trailer guy located in Santa Ana, CA. It's good to see lots of activity here.
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Post by John Palmer on Aug 4, 2014 15:03:57 GMT -8
It was a loose fitting connection at the fuse spade terminals. The loose connection caused a high resistance, resulting in enough heat to melt the plastic fuse. It was not a short, because the fuse wire did not melt.
The Cure.....Crimp the connectors a little tighter "BEFORE" you replace the fuse and try to reuse the circuit. If you cannot get a tight fitting, replace the fuse connector terminals.
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Post by danrhodes on Aug 4, 2014 15:06:20 GMT -8
It was a loose fitting connection at the fuse spade terminals. The loose connection caused a high resistance, resulting in enough heat to melt the plastic fuse. It was not a short, because the fuse wire did not melt. The Cure.....Crimp the connectors a little tighter "BEFORE" you replace the fuse and try to reuse the circuit. If you cannot get a tight fitting, replace the fuse connector terminals. Came back to say exactly this...Also cheap Chinese fuses are fairly notorious for this, so a combo of high resistance wiring and bad fuses is perhaps a more likely scenario (though I'd check your load current also). |
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John Palmer
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Hi, From a vintage trailer guy located in Santa Ana, CA. It's good to see lots of activity here.
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Likes: 579
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Post by John Palmer on Aug 4, 2014 15:14:17 GMT -8
Fuses can get reasonably hot before losing continuity. Your 40W lamp is drawing over 3A alone, so there's a good chance that your load was greater than the 5A you think it was, but not quite the 10A the fuse was rated for... A fuse "might be able" to get warm, but under no circumstances "should it ever be warm" to the touch.
A WARM electrical connection/wire/switch is a sign of a loose connection, or circuit overload, which causes the high resistance, which produces the excessive heat, and leads to the ultimate failure. I'm assuming the circuit was wired with an adequate gauge wire size. Tighten the terminals, and the heat will go away. This is true for both the positive and negative sides.
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John Palmer
Senior Member
Hi, From a vintage trailer guy located in Santa Ana, CA. It's good to see lots of activity here.
Posts: 1,638
Likes: 579
Currently Offline
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Post by John Palmer on Aug 4, 2014 15:23:38 GMT -8
It was a loose fitting connection at the fuse spade terminals. The loose connection caused a high resistance, resulting in enough heat to melt the plastic fuse. It was not a short, because the fuse wire did not melt. The Cure.....Crimp the connectors a little tighter "BEFORE" you replace the fuse and try to reuse the circuit. If you cannot get a tight fitting, replace the fuse connector terminals. Came back to say exactly this...Also cheap Chinese fuses are fairly notorious for this, so a combo of high resistance wiring and bad fuses is perhaps a more likely scenario (though I'd check your load current also). The fuse was "the result" of the problem, not "the cause" of this problem.
I've been rewiring cars for over fifty years, and never knew that "cheap fuses were notorious for melting connections". I learn something everyday, Thanks.
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Post by bigbill on Aug 4, 2014 19:32:28 GMT -8
I am of the opinion that John is right if the fuse plastic melted it was because of a faulty connection at the fuse terminals causing a high resistance which generates heat as john said either loose connection or it could possibly be excess oxidation on the surfaces of the fuse or the terminal. Blade fuses don't require anything of the plastic cover except to provide a handle and protection if something falls against them. On anything I own that sits for an extended period of time I always pull each fuse and plug it back in just to make sure it hasn't built up a layer of oxidation. Back in the days of point distributors many times after a car sat for a few months it wouldn't start so you merely took a match book cover and slide between the contacts a few times and it fired right up. This is the same problem that people had with outdoor TV antennas the connections would oxidize at the antenna and reception would fall off and interference from two way radios would increase.
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Post by vikx on Aug 4, 2014 21:57:00 GMT -8
I agree with the above. Plus: 12 volt 40 watt light bulbs are greedy pulling amps. I've seen melted wiring when people use the incandescent look a likes... Not sure why, but I don't recommend them at all.
And Chinese anything irritates me. Especially plywood. Sorry for the rant.
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