Doug Rohrer
Well Known Member
I have a -9A with an O-320. Recently I have noticed erratic negative amp readings on the G3X screen. Negative readings seem impossible because the shunt is in line with the alternator output lead, not the battery output lead. The alternator is a B&C unit with the B&C voltage regulator. The output is normal after starting and takeoff. It starts to jump around between -1 and -59 amps rapidly when the engine is backed down below 2100 RPM. The voltage is rock solid at 14.3 and the amber alternator failure light does not come on, so I am confident it is a sensor/display error rather than a real negative output. If the problem was a loose shunt connection, I would think the readings would bounce between normal and zero. I plan to call the Garmin guys, but I thought I would check with the forum first to see if anyone else has experienced this problem.