J

jtrollin

Well Known Member
I am having an issue with my alternator where when watching it via the VPX screen on my G3X it shows the alternator turning off and then on again at random intervals. This is causing my battery to drain and create havoc with my systems not hooked up to my backup battery.

I have replaced the voltage regulator thinking that might be the problem, but no luck, same issue. Anyone have any ideas on what could be going on? I plan on taking my laptop out tomorrow so I can watch the VPX logs as it happens, but thought I would ask for some ideas.

thanks,
 
The plane power alternators that I am familiar with have a self contained voltage regulator. I assume you re watching the field current on the VPX. If that's the case, it is normal to see a fluctuation in the amount of current being drawn by the alternator field. If you post your schematic it would be easier to help you out.
 
Bill,

Let me see if I can get a image of my wiring, but I followed the VPX manual. It is not the current, the VPX shows the alternator go to a power off state, like I turned off the switch, then it comes back on again at random intervals.

John
 
That alternator has the internal VR and OV crowbar. You stated you had replaced the voltage regulator, so I am a bit confused how you replaced the VR
 
They have a kit to replace it. They recommend it be replaced every so many hours, forgot the number. It was actually pretty easy to change out.
 
I can't imagine why they would recommend periodic replacement of a functioning part. I assume everything worked at some point. I would suggest you put a voltmeter on the field connector at the alternator and verify you have around .3 volts less than the battery voltage. If so, I would run the engine without the avionics on, and check the voltage at the battery, it should be greater than 13.8 volts. At this point I would monitor the voltage output to see if it is rising above 16 volts, which is about where the crowbar over voltage will kick in. This should also fault your current on the VPX field circuit. One additional thing, could your belt be loose? How many hours do you have on the alternator? PP is real good with warranty issues, send it in and have it checked out.
 
It has brushes on it that wear out over time. You are supposed to check the length of the brushes and replace if the are a certain size.
 
How many hours do you have on the alternator? I would think that it would not be unreasonable to expect 500 hours on the alternator without maintenance.
 
I had the same problem two weeks ago, It was caused by a bad alternator switch. Try turning off your alt switch on the panel and then turn on the alternator circuit in the vpx and see if it stays running.

Rob Hickman
N402RH RV-10
 
Was it working fine before for a good number of hours and now it is not, or are you troubleshooting a problem from first engine start?

An easy thing to check is to make sure the Sec Alternator is set to none (or to your secondary alternator pinout) in the configurator. If the 'Sec Alt' is set to something incorrectly, say your landing lights, it will turn off the alternator when you turn the lights on.

Also check, as Rob said, that the switch is not bad or loose switch wiring. I've had a bad switch problem too and it is easy to troubleshoot. Just look on your EFIS and it will tell you if the VP-X thinks the switch is on or off. It should match the physical state of your switch. :)
 
Marc,

I don't think it ever worked right, I just never flew long enough to notice until I flew to Florida. I will check the switch as right now that looks the most obvious and easy to test first. Wanted to go today, but it was way to cold..
 
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