scottalexander

We have a 2010 e60 with the N52k.

The trunk electronic activator latch would not operate. Upon opening the trunk with the key I pulled out the wire loom located in the right side trunk hinge. This is the BMW design fault where everyone has sheered off trunk wires from opening and closing the trunk (because the wires are channeled through the trunk hinge).

Sure enough, all the wires were destroyed from opening and closing the trunk. The brown thick wire was fully cut in half.

I could use a wire butt end connector to connect all the wires, but let's talk about soldering.

When I twist the wires together and put the solder gun on the wires to heat the wire up (so the solder can melt them together), why doesn't the extreme heat being applied to the wires, blow the fuse in the fuse box?

When wires heat up from faults, the fuse is supposed to blow. Shouldn't the heat applied from the solder gun blow the fuse in the glove fuse box?

FormerE30Owner

No. The fuse blows when a larger than design current flows through it (the fuse) and heats the fuse. The heat that you are applying to solder doesn't reach the fuse and cause it to blow.

seanjordan20

Why would it? You're not supplying an electrical current. Fuses blow on an overload/surge not because of heat on a wire

FormerE30Owner

Well, actually, the overload or higher current does cause the fuse to heat up and melt (blow, as you put it). The high load does heat the wires BTW and the fuse is there to interrupt the current before the wires heat up too much and cause a fire or melt the insulation.

seanjordan20

I thought he asked why the heat from the solder doesn't blow the fuse not heat from an overload (current). I could be wrong.

FormerE30Owner

In theory, if the soldering job is done close enough to the fuse (at the fuse terminals, for example), the heat transmitted through the wire could melt the fuse, since its melting point is much lower than the wire itself and is in fact quite close to the melting temperature of the solder. I simply answered that his soldering job was too far from the fuse to actually melt the fuse.

seanjordan20

You're right. I was not trying to respond to hypotheticals.

scottalexander

What is inside this cigarette sized case (in the attached image).

FormerE30Owner

What does this have to do with 'fuse blowing'?

scottalexander

When I was soldering the trunk lid wires back together after they were cut in half (from lifting the trunk lid open and shut after a number if years). I noticed the outside of the white box device in the picture was hot to the touch. It didn't seem right that it should be that hot.

Did heating up the trunk wires for soldering make this white box hot?

I was wondering about the function of the white box to begin with because some e60 models didn't have one mounted next to the rear fuse box.