Junior
As it was a pain to remove individual wires from connectors, this was my procedure for re-insulating the wires. I cut each wire (one at a time) and used a fishing trace ferrule to rejoin the wires.
The other problem is getting small heat shrink over the connector inserts.
Procedure is;
1. Removed all the insulation from the wires.
2. Cut one wire at mid point.
3. Determine the smallest diameter heat shrink and joining ferrule that will fit the wire 4. Determine the smallest diameter heat shrink that will fit over the joining ferrule.
5. Cut three lengths of the appropriate size heat shrink, two for the wire and one for the ferrule. The ones for the wire will need to allow the cut ends of the wire to protrude to allow crimping of the wire into the ferrule. The piece for the ferrule about 1"/25mm
6. Place the heat shrink on the wires, making sure that it goes down into the connectors.
7. Shrink the heat shrink to the wires.
8. Place the third piece of heat shrink for the ferrule on one wire.
9. Place the wires in the ferrule and crimp both wires. I used a crimp that left a "u" shaped indentation in the crimp. Test the crimping by pulling on the wires.
10. Move the third piece of heat shrink centrally over the ferrule and shrink.
11. Repeat by the number of wires in the harness.
The ferrules can be bought from any fishing tackle shop. I used the copper ones.