I have a connection that I need to make fairly often. The wires are 18 ga stranded nickle/nickel plated. It feeds a 110v volt source for a few seconds and then the wire turn into signal wires back to the control board reading 1 microamp. When replacing the 110v part that reads the signal it is usually hard to get to the control board and the easiest method would be to make a splice. I have no problems twisting the wires (wire nuts) or making a solder connection. These two methods do not seem to decrease the signal reading at all, but are usually bulky (with wire nuts) and solder connection is usually to tight to make. If I try to use butt splice the signal drops off and is unreadable for the control board, I assume the butt splice increase resistance? Is there a butt connector that would work for this application? Or another connection that might work with out this signal loss?

Are your butt splices that's crappy crimp type? I'm guessing they are. I'd recommend slipping some shring tubing back along the wire, do a western union splice, solder that... pull the shrink tubing back and shrink it. Not bulky and should eliminate your resistance problem since soldered connections apparently are good enough in your application.

There are different alloys for butt splices. Typical crimps that I have seen over the years in small butt splices are not generally sound connections and a lot can even be easily pulled apart. Smoothy's idea is good if it works for you. I had to make connections for thermocouples with butt splices. The crimps we used were uninsulated and the one we used on the compensated lead of the thermo couple was different allow, but they were not generally an issue, but you don't buy them at Home Depot either. We did have to put heat shrink over the splices after they were complete. If you know thermocouples, the voltage is small and resistance can alter the reading. I guess what I am saying is there are products out there that do work, if you can locate a distributor and if it is worth the cost and hassle and you use the right crimp tool.