Do a good 3 wire splice/tap is not easy to do. Here is my method, which is also what I do for a 4 wire splice/tap.
- Start with butt splice that is one size LARGER than is required
- Strip all wires
- Twist together 2 from different circuits (in the picture above, the back and on blue)
- Insert and crimp this into one end of the butt splice
- Use a piece of scrap wire (or the fourth wire)and do the same for the remaining wires. Trim the scrap off and close to the splice as possible.
- Heat shrink (either a separate piece or use shrinkable insulated butt splices) are a MUST !