What were your symptoms before you changed the wiring harness on you RadCity 5+?

I have both Step thru 5 P & High Step 5 P:  Make sure your tires are firm and not under-inflated.  You should have 27 x 2.00 or 27 x 1.95 tires. I recommend no less than 63 to 64 PSI. in each tire.   

Radcity 5 plus (Step-Thru & High-Step: I use 64 PSI.  It coasts longer and the tires wear is "longer" and "even" over time.  Also, you have less chance of object puncture.  An under-inflated tire is more acceptable to object puncture and unstable steering and a short life.  The same principle applies (1 lb under the max PSI) to automobiles and motorcycles, etc.   It's a firmer ride; but you'll save $$$ in the long-term and maintain better steering control and performance.