ramireo:

Sounds like you have either or both of two problems.

The base metal to be soldered (not welded) must be at or above the melting temperature of the solder, and it must be clean.

Sand or scrape the two pieces to be joined until you see bright metal. Brush flux on both parts, and heat them with the iron. Then dip the end of the solder in the flux and touch it to the base metal.

If the solder does not melt and flow you don't yet have the parts hot enough. You can sometimes help by touching the solder to the iron, this will help heat flow, and assist in heating the base metal.

It is also possible your iron is not strong enough for the landing gear wire, you need a minimum of 100 Watts for that, but even a 25 Watt should be enough for the pull-pull cables. You might be able to do the push rods with a 25 Watt - the 25 Watt is more for wiring than for construction.

Hope this helps.

Bill.