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Electrical failure

T

TShort

Well Known Member
All-

Looking for some input / wisdom in troubleshooting an electrical issue.

This is the RV-10 that I bought flying, and I don't know the electrical system as well as I would had I built it. Unfortunately, there is no schematic.

I have a new Plane Power alternator (we installed it during the prebuy ~50 hours ago), and a new Odyssey PC925 battery.

Yesterday enroute from KUMP -KOZS (Camdenton, MO) we experienced a total electrical failure about 20 minutes out from OZS. Everything went offline except the 2 EFIS screens (internal batteries). Over the next 5 minutes or so, power came on and off intermittently. I turned off everything but one EFIS screen, the SL30, and the transponder (as I was squawking and using VFR flight following).

The initial shutdown (as best I can recall) happened when I hit the push to talk to transmit.

The master and alt field switches are circuit breaker switches. No breakers popped. Cycling the switches made no difference.

After I shed loads at some point the power stayed on. Volts were at 12.6 and the "ALT" warning light on the panel was illuminated.

I was able to make the approach and landing uneventfully; flaps and fuel boost pump worked fine without any additional power glitches.

I'd appreciate any thoughts / advice on troubleshooting.

My plan today is to go out and check all the wiring that I can access, make sure nothing is loose, etc. I dumped the data from the EFIS (AFS3500) yesterday but forgot to grab it, so I am going to download that and see if there is anything enlightening there.

Thanks in advance.
 
Thomas,
Look closely at the alternator field wiring, pins, etc.
On mine, the pin inside the alternator connector fatigued from vibration and broke (not properly supported due to a missing connector insert/grommet).
Replaced and RTV'd the wires in the back of the connector.

Good luck!
 
Yep - you lost alternator output.

Based on what you said, you were flying on just the battery for an extended period of time before you realized you had a problem (you keyed the mic and the current drain dipped what was left of battery voltage).

After you fix the alternator problem, recommend resetting your EFIS low voltage alarm to something like 13.5vdc. That way you will get an alarm just as soon as you loose the alternator.

Carl
 
Set your EFIS Amps gauge so that it will warn you if you get below 10 amps.

Rob Hickman
N402RH RV-10
 
Rob is dead on, and as well you should check the yellow and red ranges on your voltmeter. Set the Yellow for 13 and the red for 12.5. Most alternators will run above that under normal load, and you will get a warning if the alternator drops off line and the voltage drops. Catching it here will allow you some time to shed loads as you desire.

Vic
 
Carl Froehlich said:
Yep - you lost alternator output.

Based on what you said, you were flying on just the battery for an extended period of time before you realized you had a problem
Carl
Click to expand...

Interestingly, based on review of the EFIS data download, it was only 1-2 minutes. I think there is a second issue, as the battery should handle that load for quite some time.

N402RH said:
Set your EFIS Amps gauge so that it will warn you if you get below 10 amps.

Rob Hickman
N402RH RV-10
Click to expand...

Can you clarify? The builder has "AMPS_SHUNT" displayed, which seems to show amps being pulled from the battery (I don't know if I understand this correctly)

Do you mean set the red zone as over 10A draw?

vic syracuse said:
Rob is dead on, and as well you should check the yellow and red ranges on your voltmeter. Set the Yellow for 13 and the red for 12.5. Most alternators will run above that under normal load, and you will get a warning if the alternator drops off line and the voltage drops. Catching it here will allow you some time to shed loads as you desire.

Vic
Click to expand...

That's around where I have them; I had the audio alerts off, at the time this happened.


Thanks for the input so far.

I pulled the cowl today and went through everything. Using the plane power troubleshooting flowsheet, it looks like there was an internal failure in the alternator itself. Another is enroute.
 
N402RH said:
Set your EFIS Amps gauge so that it will warn you if you get below 10 amps.

Rob Hickman
N402RH RV-10
Click to expand...

that may or may not be applicable, my amp meter is set up as a load meter and will not show any difference with or without the alternator on line. the volt meter is primary indicator for alternator failure.

bob burns
RV-4 N82RB
 
Also check your battery terminals. I had a similar experience once and it was a loose battery terminal.
 
DanH said:
Maybe, maybe not. A connector failure in the supplied plug looks like an alternator failure.

http://www.vansairforce.com/community/showthread.php?t=125262
Click to expand...

I remember reading that thread a while back, thanks! I checked the connector and pins when troubleshooting - looked OK. I will try squeezing them when I go back out to the airport before pulling the old alternator...

If I had as much time building as I have reading VAF my -8 would probably be done, twice!

Thanks for the input so far.
 
We recommend that you place the amp meter shunt in the alternator line so you can always see what the actual alternator output is. In normal operation the alternator output would be the panel power + battery charge current. Once the battery is charged after an engine start the alternator output is panel current. If you have an alternator failure the amp meter will immediately drop and the voltage will drop as the battery tries to keep up with the load.

If you place the amp meter shunt in the battery line it will display positive current as the battery charges, zero when charged and negative if the alternator fails. The problem with this setup is you never have any idea how much current your panel equipment is using and you have no idea how hard your alternator is working.

I had an alternator failure last year in my RV-10 and it ended up being a broken plug that connects to the alternator field. Unfortunately I did not have a low amps warning set in the EFIS and my red low voltage warning was set to 11 volts. I discovered the failure when my IFD540 started failing just as I was about to shoot an actual IFR approach into Boeing field. After reviewing the data logs I discovered that the Alternator had failed 45 minutes earlier.


Rob Hickman
N402RH RV-10
Advanced Flight Systems Inc.
 
TShort said:
I remember reading that thread a while back, thanks! I checked the connector and pins when troubleshooting - looked OK. I will try squeezing them when I go back out to the airport before pulling the old alternator...

If I had as much time building as I have reading VAF my -8 would probably be done, twice!

Thanks for the input so far.
Click to expand...
Mine looked okay too, but after pulling the alternator, finding a local alternator shop (a rare thing these days) and having it test "good", I started looking harder. A test pull of each wire from the back of the harness plug revealed the issue.
 
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