Rewire Essential Bus
April 2005 - The first weekend of April I after doing the final installation of the cowls I took the instrument cover off to investigate an intermittent problem I keep having on my essential bus. The problem first appeared in my 2004 cross country trip when we landed in New Mexico and couldn't get the gear to extend once we were ready to takeoff. I eventually traced it back to the diode bridge that isolates the essential bus from the main bus in the event of an alternator failure. The essential bus can be fed current from the battery directly without any current continuing to the main bus. The diode bridge was loose against its heat sink, so I figured it had overheated. After tightening the device against the heatsink I didn't have a re-occurrence the rest of the trip.
However, toward the end of 2004 the problem re-surfaced and upon checking the diode bridge, it was still secure against the heatsink. Hmmm? Well, I started to look at the wiring and loads and realized I was probably overloading the essential bus with too many "non-essential" items so I moved those circuits to the main bus. The wiring itself to the essential bus is only 16 gauge so it shouldn't carry more than 12.5 amps continuous. I was slightly over that with the load I was carrying. My main bus is completely filled now, so I may share some circuits in the future if needed. I'm not convinced this will correct the problem, but short of replacing the diode bridge I see no other cause for the problem.
Last Updated on July 12, 2008