Electrical problem

[Kjkbcaptain@aol.com]

When I turn on the IBBS it shows 12+ volts and 0 on the battery bus. Then when I turn on the master switch, nothing happens. Battery bus still shows 0, lights, fuel pump, etc. are not powered. Main 40 amp fuse is good, master switch in the panel tests good, main battery is good. I assumed the problem was the master relay so I replaced that but I still have the same problem. Suggestions??

[Andy]

Suggestions??

Where are you reading IBBS volts? Is this a VFR panel or a G3X panel? In either case 12.0 V seems very low for IBBS voltage so IBBS may not have been charging.

There isn't much that can stop MAIN bus being live if battery, master solenoid, and Master switch are good. Do you hear the solenoid operate when Master is turned on? If not then check the voltage at each of the master solenoid terminals with master off and with master on. The results should tell you where to look for the problem.

My "Main Wiring Schematic" does not show master solenoid terminal numbers so you may have to report your results using wire number or with a sketch.

[Andy]

I have two versions of schematic "Power Distribution and Start Circuit" and both seem to show incorrect connection of the master solenoid coil quench diode.

In the configuration shown the diode is between the coil positive side and ground and the coil negative terminal is open circuit when Master is opened. That means the full back EMF appears across the opening Master switch contacts and will likely cause arcing and early failure of the switch.

The conventional location for a solenoid quench diode is directly across the solenoid coil as is shown for the starter solenoid.

Pete - Is there a later version that revises the master solenoid diode connection?

[Pete D]

There is an update pending but nothing released yet for changing the diode attachment points. Everything built to date is per the published schematic and there have been very few issues to date.