GRT Ammeter fluctuations

[YellowJacket RV9]

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

[GalinHdz]

Originally Posted by YellowJacket RV9

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

Physics (P/I=E) makes it impossible to have wildly varying amperage with no change in voltage so it is a sensor or display problem. I had the same situation and it turned out to be a bad connector. In hindsight I should have just cut the 3 wires and made all new connections. It would have been a lot faster and with less headaches. YMMV

[YellowJacket RV9]

Originally Posted by GalinHdz

Physics (P/I=E) makes it impossible to have wildly varying amperage with no change in voltage so it is a sensor or display problem. I had the same situation and it turned out to be a bad connector. In hindsight I should have just cut the 3 wires and made all new connections. It would have been a lot faster and with less headaches. YMMV

Thanks for confirming my suspicions! Time for some quality time on my back...

Chris

[DennisRhodes]

I just experienced same thing however was with a Dynon using a shunt arrangement for the mv signal readings. Turns out it was a couple bad crimp connectors on the shunt signal wire connections. I also saw the amps change without a voltage change. Can t happen!