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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?
 

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Nuclear engineer
02/2012 X5 35d M57Y CPO 99K miles NOKIAN WR G3 12K miles
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17,449 Posts
Excessive electrical current through the conductor wire blows the fuse to prevent excessive heat (current squared times the resistance of the whole wire). The fuse is made of a metal alloy that melts at lower temperature than the copper wire.

The solder does not ***8220;melt the wires together.***8221; The solder is, again, a metal alloy with a very low melting temperature and it forms another alloy at the junction with the copper wire to make a good electrical connection. The solder may include a chemical core that helps with a good joint.
 

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2006 530xi 6 MT
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Also, consider that the heat applied to the wire and solder would have to travel to where the fuse is located. That isn't happening. The wire may be hot a few inches away, but it is not hot at all feet way. It take much more heat to blow a fuse than soldering a typical wire. As an example, I just replaced a backlight fuse on a MacBook Pro a couple weeks ago. Very small surface mount 2A 32V fuse in a 0402 package, about 1mm x 0.5mm. Extreme magnification to even see soldering this sucker in place. I applied the soldering tip to each end of the very tiny fuse and it was fine. The datasheet details soldering profiles and depending on the soldering method you use, you have even 10 seconds at the highest temperature and up to a minute at some lower temperature methods.
 
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