Hi all,
Today while returning from NC to FL, I noticed that for occasional periods of several minutes at a time, my GRT engine monitor / EFIS would show wildly fluctuating amp readings, all negative, from -1 to -38 or more. While this was occurring, the voltage stayed rock steady at 14.4V. Turning the ALT field off did not change the readings at all, they kept fluctuating. Cycling the ALT field did nothing as well.
My GRT hall effect sensor is in GRT's recommended location, monitoring the alternator output before it comes into the ALT breaker. While flying it shows the current the alternator is providing to the electrical system, including battery, as positive amps (usually around 5-6). With the engine or alternator field off, it normally shows 0 amps.
So my inclination is that this is a sensor problem, as there were no other signs of trouble. My question is if there are any possible alternator or other failure modes that could actually cause those type of readings at that location - it would mean current running INTO the alternator, from the battery. To be honest, I'd rather replace an alternator than lay upside down under the panel for hours chasing down a loose connection! On landing of course, all readings were normal.
Chris
Today while returning from NC to FL, I noticed that for occasional periods of several minutes at a time, my GRT engine monitor / EFIS would show wildly fluctuating amp readings, all negative, from -1 to -38 or more. While this was occurring, the voltage stayed rock steady at 14.4V. Turning the ALT field off did not change the readings at all, they kept fluctuating. Cycling the ALT field did nothing as well.
My GRT hall effect sensor is in GRT's recommended location, monitoring the alternator output before it comes into the ALT breaker. While flying it shows the current the alternator is providing to the electrical system, including battery, as positive amps (usually around 5-6). With the engine or alternator field off, it normally shows 0 amps.
So my inclination is that this is a sensor problem, as there were no other signs of trouble. My question is if there are any possible alternator or other failure modes that could actually cause those type of readings at that location - it would mean current running INTO the alternator, from the battery. To be honest, I'd rather replace an alternator than lay upside down under the panel for hours chasing down a loose connection! On landing of course, all readings were normal.
Chris
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