O Gauge Jim posted:Most tend to use larger than necessary wire when re-wiring components in a locomotive. I use very flexible wire, size 22 and buy it from Amazon. The number 22 flexible wire is also excellent for rewiring from the pick up rollers to lighting inside of passenger cars and cabooses, also from the pick up rollers to the whistle mechanisms in tenders.
Also, if I am extending the length of an existing wire such as you plan to do on the e-unit, I cover the connection with shrink tubing rather than electrical tape. The shrink tubing is permanent while the electrical tape is not only difficult to apply neatly, but bulky and overtime will start to come apart.
Jim
I also use the super 22 gauge flex wire on my prewar rebuilds. Not like the original cloth covered wire it has a silicone jacket (buy mine in black) and over 100 strands of the twisted wire. Very flexible and will last. 
If you are worried about the current draw check your loco with a amp meter and see what it draws and also google the current capabilities of the wire.
