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  #1  
Old 03-21-2017, 11:36 AM
dg1651 dg1651 is offline
 
Join Date: Feb 2016
Location: Evanston
Posts: 3
Default Amp draw fluctuating!!

OK , I have been reading anything I can find on this forum but to no avail. I have a RV6A with a Vision Microsystems engine monitoring system. During my last flight the Amp draw fluctuated quite a bit. It would go from 30 amps to 40 back to 30 then all the way up to 50 60 and even 65. That is red-line on my amp gauge and I was concerned so I switched the alternator off. (reading these forms maybe not the best thing to do repeatedly as I did) This would usually take a few seconds then the apm draw would indicate 1 or 2 or very low like that. After a few min I would turn the alternator switch back on and it would stay steady for a few min then start going up and down. The volts remained steady at 14.XX I would wait until it got to over 60 amps and turn the alt switch off again. This happened probably 5 times in a 1 hour flight. only once when I had the alt switch off did the amps remain around 30 for a few min with some more fluctuating before finally dropping to nothing. Is this a sign of bad alternator? Where should I start for troubleshooting?
Thanks
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  #2  
Old 03-21-2017, 11:47 AM
BillL BillL is offline
 
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Location: Central IL
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So many things. You may want to buy the Flir adapter for your smart phone.

If it is a short, then surprising it did not blow the ANL fuse, do you have one?

It could be a loose connector/connection downstream of the voltage sense wire and it's resistance drawing higher amps (my favorite)

It could be a device that is acting badly, but would likely blow the breaker/fuse.

It could just be a bad amp meter??

I would run the system off a ground power supply where you can see it's supply amps and then begin trouble shooting.

The FLIR could quickly identify a hot joint or wire or a loose terminal fastener were it is it is hotter than everything else.

If it were mine the Flir would be justified. ($250) I just had an electric garage heater with a loose joint that bumped up the amps from 30 to 45 and smoked a section of wire it still worked just fine. Lucky I found it.

The old adage for a short to ground wire is bypass the fuse and "follow the smoking wire" approach, although not literally. . . . . well maybe. It really works but not recommended for an airplane.
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Op Lims in hand 12-7-17
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  #3  
Old 03-21-2017, 11:49 AM
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Mike S Mike S is online now
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Location: Dayton Airpark, NV A34
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Default Welcome to VAF!

David, welcome aboard the good ship VAF

You may end up chasing this gremlin for a long time-----lots of things could be causing the problem you describe.

First off, look for any loose connections. Make sure all screws or nuts are tight where a ring lug is used to terminate a wire. Make sure all slide on blade connectors are secure, they should not wiggle.

Check all wires that are crimped into any form of connector------butt splice, ring lug, blade etc. Wiggle and pull the wire to be sure it is in the connector securely.

Check all grounds from the battery all the way through the entire system.

Look for any loose wire that could be shorting on the airframe.

Check for both the master and starter contactor to be operating correctly.

You could try another flight and start pulling one breaker at a time to isolate various pieces of equipment and see if the problem can be isolated to a single source-------this would make the search much easier.

Good luck................
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Last edited by Mike S : 03-21-2017 at 11:55 AM.
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  #4  
Old 03-21-2017, 12:41 PM
dg1651 dg1651 is offline
 
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Thank you Bill and Mike for your responses. I will look into a FLIR and in the meanwhile start checking connections.
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  #5  
Old 03-21-2017, 01:02 PM
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Noah Noah is online now
 
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I'd be surprised if this is not an instrumentation issue, since you are not seeing fluctuating voltage along with current. If your current draw was fluctuating this much, I would expect to see at least a couple of tenths of a volt fluctuation. Do you have a shunt or a hall effect sensor for current measurement? If it were me, the first thing I would do is disconnect your current sensor input to your monitor and see what the indication reads when disconnected. Does the current go to 0? Or 100 amps? Then I would rapidly reconnect and disconnect it and see if the indication is similar to what you are seeing in flight. If it is, I would look for a bad connection in your signal line or the ground to that sensor.
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Old 03-21-2017, 01:38 PM
BillL BillL is offline
 
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Quote:
Originally Posted by Noah View Post
I'd be surprised if this is not an instrumentation issue, since you are not seeing fluctuating voltage along with current. If your current draw was fluctuating this much, I would expect to see at least a couple of tenths of a volt fluctuation. Do you have a shunt or a hall effect sensor for current measurement? If it were me, the first thing I would do is disconnect your current sensor input to your monitor and see what the indication reads when disconnected. Does the current go to 0? Or 100 amps? Then I would rapidly reconnect and disconnect it and see if the indication is similar to what you are seeing in flight. If it is, I would look for a bad connection in your signal line or the ground to that sensor.
Good chance too, that was the reason for the GPU with an amp meter.
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  #7  
Old 03-21-2017, 02:03 PM
dg1651 dg1651 is offline
 
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Again thank you for the response. This is my first time really attempting to work on this plane, or any plane, so I am sure alot more reading and googling and patience will be needed. I will see what I can do and will update once I have had a chance to get the cowling off.
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  #8  
Old 03-21-2017, 02:04 PM
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sirlegin sirlegin is online now
 
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I just had exactly the same thing happen to my 9A. Dynon D10 amps were up in the 30's and 40's with 14.2 volts being generated.
I noticed the last couple of times I flew the prop did not spin as fast on startup.
I checked all the fittings, wires etc and checked that there was not a short circuit when everything was off.
Turns out my 3 year old Oddessey PC680 had basically given in. Replaced the battery, I have 2 batteries, the secondary was fine (I use both to start) and everything is back to normal.
Hopefully yours will be as easy to fix.
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  #9  
Old 03-21-2017, 02:31 PM
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Raymo Raymo is online now
 
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A similar issue occurred to a Cessna at the airfield recently. The new PlanePower Alt would randomly put out max amps. It eventually stuck there. Connections, regulator, etc were checked by two mechs and found nothing wrong.

Another mech wiggled the large output wire that connected to the alternator, which had two or three layers of heat shrink. The heat shrink made it feel like a good connection but its removal revealed a broken wire that had just enough contact to cause the amps to jump up and down. A few wire strands were melted into nice shiny little balls (arcing). The regulator would see the weak output as a need to ask for more, which the alternator ready attempted to send.
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  #10  
Old 03-21-2017, 02:58 PM
DennisRhodes DennisRhodes is offline
 
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"help troubleshooting an electrical gremlin" . Search for this thread. Sounds close to problem I had, equipment was a little different but amp fluctuations were same. I also thought alternator and actually installed a new one. But it did the same thing.
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