Amp reading on Skyview HDX

[Lon]

I want to confirm that the Amp reading on a Skyview HDX shows the difference between the amps flowing to the plane's battery minus the amps being drawn from the battery by the plane's electrical system.

My RV-12 is equipped with a Rotax 912ULS. The Rotax generator puts out about 14 amps (continuous, in flight). So, as I understand it:

If the plane's electrical system is drawing 12 amps (for things like the HDX displays, radio, transponder and the like), then the HDX will display 2 amps.

But if the HDX displays negative 2 amps (-2), that means that my plane's electrical system is either
-- drawing 16 amps (while the generator puts out 14 amps), or
-- drawing 12 amps (but the Rotax generator is putting out only 10 amps).

Is my understanding correct? I ask, because my HDX suddenly began to display negative 8 to 10 amps (-8 to -10) and the battery's voltage is steadily declining. I suspect this means that the Rotax generator is no longer charging the battery.

 

[sunfish]

I suggest checking your Rotax voltage regulator, they seem to fail occasionally.

 

[Lon]

I suggest checking your Rotax voltage regulator, they seem to fail occasionally.

I have checked and replaced my voltage regulator, but the problem remains. Tomorrow, I'll check the stator. I want to confirm that when my HDX amp reading says -8 or -10, it's telling me that my plane's electrical system is drawing 8 or 10 amps more than the voltage regulator is supplying, and that's why the battery's volts are declining.

 

[Raymo]

I think you are confusing volts and amps. Your alternator should put out around 14 volts. Amp output is dependent on the load of various devices in the aircraft. As noted in the installation manual, the Skyview system will show amps depending on where the shunt is connected in your system.

See page 7-62 of the 15.4 (AE) version of the installation manual.

• Position A – Ammeter indicates current flow into or out of your battery. In this position, it will show both positive and negative currents (i.e., -60 amps to +60 amps).
• Position B–Ammeter indicates only the positive currents flowing from the alternator to both the battery and aircraft loads. (0A-60A)
• Position C–Ammeter indicates the current flowing only into the aircraft loads. (0A-60A)

 

[Lon]

Raymo, Thanks. My Dynon is connected in Position A. The Dynon ammeter used to show current flow into the battery after engine start-up and during taxi and flight; but it now shows current flow out of the battery, all the time. When it shows current flow out of the battery (e.g., "-8" amps), the Dynon voltmeter shows the battery voltage slowly dropping, 0.1 volts at a time, quickly enough that the voltage drop can be seen by watching for just a short time. I am seeking to confirm that the reason my ammeter shows negative amps is that the rectifier/regulator is not producing enough DC current to power the plane's equipment, and therefor the battery is supplying the additional electricity that equipment requires. One of the reasons the rectifier/regulator may not be producing enough DC current is that the stator may not be producing AC current to feed the rectifier/regulator. Is that right?

 

[RVDan]

The symptoms you are observing are typical of an alternator or regulator failure.

 

[Raymo]

Lon,

See the following link for troubleshooting steps. Different alternator MFG but the process is the same.

Troubleshooting

planepower.aero