Melted fuse holder...why didn't the fuse blow??? (Pics)

[dawson444]

The pictures below are of the fuse holder for my rock lights. They are 6 -55 watt lights. I had them wired to 2 relays, however I was using one power supply wire.

When I re do them I plan to install a separate power supply for each relay. My question is though, why did the fuse melt like it did? It would seem like the fuses's job to blow before enough amps allows that to happen. The same sort of thing happened to one of the relays (but it still works).

According to some calculations the 6 55 watt lights should have drawn around 27.5 amps. So theoretically the 30 amp fuse should have been ok. I know nothing is perfect and that over time they may have ended up drawing more than 30 amps. But why then didn't the fuse just blow? Thanks!

 

[dawson444]

Also, the very melted side was the side going to the relays, not the side closest to the battery. One of the light bulbs was blown too, it was an H3 and it seems like the entire element had come loose in the bulb and was floating around, the element didn't break like what usually happens when a bulb burns out.

 

[Jason4x4]

could have been a loose connection, or the wire isn't big enough to handle the 27 amps.

 

[cegusman]

Cheap fuses will do that. They wont pop when they need too. There was a thread either here or on pirate about the cheap harbor freight fuses doing the same thing.

 

[YZEATER]

to big a fuse?

 

[mike n]

Cheap fuses will do that. They wont pop when they need too. There was a thread either here or on pirate about the cheap harbor freight fuses doing the same thing.

I read a GM service bulletin recently about the HF/Storehouse fuses being junk and not blowing at the specified amperage.

Must be lead in Chinese fuses?

 

[onetonbb74]

if the amperage is under rated spec and the connections are weak, there will be too much resistance and heat will buildup which will melt insulation while never exceding the amperage of the fuse. Over time, it will look like that.

 

[dawson444]

thanks for all the replies. I don't think it was the cheap fuse thing, it was a Buss fuse. I'll redo all the connections on the supply side and rewire it for two supply wires instead of having it all run off of one.

 

[RockinChevy]

My fuse holder and relay (for the VIAIR compressor) melted just the same way, replaced it 3 times then gave up on it. I think there was a mix of 14-16 guage wires in my setup. I thought it was from my compressor from running constantly without shutting off for cool down. So anyway, I'm being a bit more careful on how I hook up my stuff.

 

[Blue85]

Well the fuse holder came from Radio Shack, so what is the question?

Any cheap fuse holder, which includes most of those in-line ones, will be made with lousy crimps to the wires. Those connections are OK for a couple of amps (at least when they are new) and get worse over time. A bad connection = resistance = heat.

Moral of the story is that unless that style of fuse holder is known to be a high quality one, it should never have any more than a 3-5 amp fuse in it.

 

[Blue85]

BTW: 6 55W lights on one fuse? You should use a maxi fuse with a large fuse holder. A better approach is to split that into 2 or 3 circuits, each on it's own fuse. This has the added advantage when a light fails/shorts, since you still have some working.

 

[BKinzey]

I'll second Blue85 statements except one. Re-rating a 30A fuse holder to only 3-5A is way overkill. If you must keep your one wire power get a 40A fuse holder & rated wiring and then put a 30A fuse in it.

 

[Blue85]

I'll second Blue85 statements except one. Re-rating a 30A fuse holder to only 3-5A is way overkill.

That would be true if it were actually good for 30A. But it has already been proven that it is not. Those designs are just weak. It is probably good for peaks of 30A, such as starting a fan motor, but obviously not continuous duty because there is not enough contact area between the wire and the terminals.

 

[BKinzey]

Uh, yea He's shown running 27.5A through it caused a failure. So you wouldn't run more than 5A through a new one of the same manufacturer? I stand with my previous statement. That's way overkill.

From looking at the damage and reading he plans to run a second power wire he should have no problem using two of those fuse holders with a 15A fuse in each.

 

[Blue85]

I agree, if he has two GOOD fuse holders with 15A fuses, the setup will work fine. My point is about crappy fuse holders. If you want reliability, you can't trust those things with much current. I've seen them melted with good 15A fuses in them as well.