Ovation backup alternator test

[Tommooney]

I went thru the poh test of the backup alternator today during runup. It all goes per poh but i see a large negative amps so im wondering how do I know it is producing electricity properly?

The poh test uses 1500 rpm, while it says best performance is at 2500 rpm?

Thanks for any help.

[Slick Nick]

If you're getting negative amperage it means the battery is discharging. Do you not have a "High / Low Volts" annunciator? What's the voltage showing while the ammeter indicates discharge? 

[GeeBee]

2 hours ago, Tommooney said:

I went thru the poh test of the backup alternator today during runup. It all goes per poh but i see a large negative amps so im wondering how do I know it is producing electricity properly?

The poh test uses 1500 rpm, while it says best performance is at 2500 rpm?

Thanks for any help.

Try going to 2000 RPM and you should have close to 0 amps and 27 -28 volts. Basically when you turn off your main alternator, look at the negative amps, turn on the backup,  if you see it get closer to 0 you got a good test, but 2000 RPM should be definitive.

[Tommooney]

Ill try that tomorrow. I suspect its not working. Thanks

[MatthiasArnold]

6 hours ago, GeeBee said:

Try going to 2000 RPM and you should have close to 0 amps and 27 -28 volts. Basically when you turn off your main alternator, look at the negative amps, turn on the backup,  if you see it get closer to 0 you got a good test, but 2000 RPM should be definitive.

^^^^This

[GeeBee]

7 hours ago, Tommooney said:

Ill try that tomorrow. I suspect its not working. Thanks

If it is not working, the most common failure point is the diode in the field wire. So check that before removing the alternator.

 

[buddy]

It’s probably your coupling on the standby alternator, I’ve had to replace mine a couple of times. Take the top cowling off and turn the prop by hand and see if the standby alternator is turning. Easy job and Spruce probably has the coupling. 

[Mark89114]

As someone who has struggled with this issue, i.e. standby not making electricity, I checked all of the easy ones, field wire, coupling, etc.

Took a call to Brian K, who led my mechanic down the path of what to look for.  Some wires had come loose behind the circuit breaker panel and he then had to dig into it to get it repaired.  You could see where the lose wires had arced against something inside.  I will see if I can find the pictures.  I might have posted them on mooneyspace    

[rgpilot]

If you find the coupler is bad, get a replacement from BC. They are more robust than others.