Good Day,
A year ago I installed a set of 16 inch Caralini Apes. I received wire extension kit with it. I matched up wires, soldered, heat shrank and re ran wires. Reconnected Deutch Connectors and all was well. But now on 3 occasions I have had the main lead for headlight low beam burn out. I usually just cut off old deutch pin, stripped and reattached another. I figured I crimped pin improperly. Well 3 times a charm. What could be causing this to keep happening? Bad Solder? Bad Ground? Bad Wire from Kit? I have attaches photos below. Any input would be great!

 

What headlamp? That looks like too much power draw through the circuit. Some aftermarket headlamps draw more current than stock. That is the reason people use relays for them. Keeps the power draw through the switch circuit low.

 

From the front of the bulb its a 55W H4 I believe. No tint to it.

 

Something in the circuit is going to ground, causing too much draw, overheating the wire.

 

Looking at the picture and the localized melting, I'd have to diagnose it as a bad crimp....or the wire may have been partially cut where it crimps to the insulation.
Are you using the proper tool?

 

No Sir, I infortunately don't have a Deutch Crimper.. I used needle nose to bend the clips on Deutch Pin. May have to use a shop to crimp properly

 

Well, I've done that too when I didn't have the right tool.

I have 40+ years in high tech and military electronics (mostly Power Electronics). I've seen lots of failed power connections...and that one has definitely failed. Make sure the soldered connection is good before you crimp.

 

If something were going to ground, it would cause the fuse to blow (the fuse is sized so that it will blow before the wiring overheats).

I agree with the others, that melted insulation was caused by a poor crimp, which causes a bad connection, resulting in overheating due to the high resistance.

There is no soldered connection in a Deutsch connector.

 

Did you strip the wire before crimping, I can see insulation under the crimp.
Are these stamped prongs from HD, I prefer using the solid gold plated type from bates racing.