How to Build a Wiring Harness - Muscle Car DIY Jun 27, 2015How to Build a Wiring Harness. June 27, 2015 by Muscle Car DiY. This chapter covers the last major topic—harness basics. In addition, I’m going to present a number of examples that tie together what you’ve learned in the first eight chapters of the book. I chose examples that I feel most readers of this book will be likely to attempt. A9l vs C3w1 Wiring harness - EECTuning Jan 31, 2013But since my wiring harness is a custom modified harness that I have no clue whether it was from an auto or manual, I can't say with experience, why swaps sometimes burn up EECs. I just wanted to let it be known that you CAN run a manual transmission with an EEC that was originally meant to operate in an automatic-equipped vehicle.