Our early fleet of electric vehicles all struggled with range in the wintertime. A used 2011 Leaf had a range of 85 miles in the summer, but only 50 miles in the winter. A Chevy Bolt EV in 2017 had a range of 230 miles in the summer, but again the winters took it down to 160 miles. What did they have in common? The cabin heat was created by the high voltage pack heating antifreeze for the heater core. How old school.

High voltage (HV) is isolated from the chassis for good reasons. When any high voltage part has a connection to the chassis, that could spell trouble, depending on how much current the connection can carry. The engineers have cleverly designed circuits and strategies that can determine a “lack of isolation” and report that to your scan tool and set a warning light. How does that detection system work?

This article will compare the low voltage system to the high voltage system and explain how a 12-volt brain can get confused. It is essential that you master the principles of electronic controls, reprogramming, oscilloscope usage, reading wiring diagrams and all aspects of electronic systems used in today’s modern vehicles in order to transition into high voltage systems.

What if the only thing you learn is to stay away from “orange cables?” How will we ever transition to electric vehicles? This is the first article in a series. In each edition we will offer you a new lesson in repairs of hybrid and electric cars and trucks.