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  #1  
Old 11-08-2019, 08:32 PM
lon@carolon.net lon@carolon.net is offline
 
Join Date: Aug 2015
Location: Santa Monica, California
Posts: 86
Default No Joy with Diagnosis of Negative Amps & Declining Volts

My RV12 is equipped with dual Dynon Skyview HDXs ("SVs"). Until recently, the Amps and Volts displayed on the SVs were exactly what they were supposed to be. Now though the SVs display negative Amps -- anywhere from -4 to -12 Amps, depending on how many of the plane's components I've turned on -- and declining Volts.

The plane has a Rotax 912ULS engine, and many planes with that engine have this identical battery charge issue. My mechanic has done all of the things recommended in other threads here on VansAirforce.net
- He secured the connections to the Ducati Rectifier/Regulator.
- He replaced the Rectifier/Regular with a new one, because the old one had blisters on its back.
- He tested the voltage output of the stator and of the new Rectifier Regulator, both of which were what they should be.
- He improved the grounding of the Rectifier/Regulator by sanding the firewall to which it is bolted; and he added a ground wire attached to the battery's negative terminal.
- He changed the Rectifier/Regulator again, in case the first new one was defective right out of the box.
- He charged the plane's Odyssey PC680 battery. And I replaced that battery with a brand new Odyssey PC680 battery.

None of these things helped. The engine starts immediately and runs smoothly. But:

- The Skyviews still display negative Amps and declining Volts.
- Also, both SVs turn on as soon as the Master switch is turned on, but after just a few moments, the co-pilot side SV blinks off and reboots.
- Finally, the digital checklist I added to the SVs no longer stays on, the way it used to. Now, after a short time, the checklist blinks off and is replaced by the moving map (which is the default item for the right half of my displays).

The only change to my Skyview setup that I've made is that shortly before the battery charge problem began, I installed Dynon WiFi Adapters. They worked fine for a couple of flights, and then my iPad Mini began dropping the WiFi signal.

I now wonder whether my problem is with the Dynon Engine Monitoring System, rather than the plane's charging circuit. That is, I wonder whether the failure of the old Rectifier/Regulator -- or something else -- damaged the circuit that senses, reads and displays Amps and Volts, so the SVs now erroneously display negative Amps and declining Volts.

Any thoughts about what my problem might be, or what to do next, would be deeply appreciated. Right now, I'm the stressed owner of a handsome assembly of used airplane parts, without a clue about what I can do to turn those parts back into the wonderful airplane it used to be.
__________________
Lon Sobel
Santa Monica, CA
RV-12, N58CV
VAF Dues Paid

Last edited by lon@carolon.net : 11-08-2019 at 08:58 PM.
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  #2  
Old 11-08-2019, 09:25 PM
NinerBikes NinerBikes is offline
 
Join Date: Dec 2018
Location: Granada Hills
Posts: 305
Default

I'm hazarding a guess here, but I believe you should try and disconnect one of the Dynon HDX screens completely, and just run one screen, and see what you get for Voltage and Amps.

Short of that, ask Dynon what the voltage and current draw is for each HDX unit., and what you have running in the backround.

The HDX, I believe is rated for up to 30V, on a 24V system, so current spikes doing damage is probably highly unlikely. However, the lower the voltage you run, the higher the current or amps you draw. You need at least 22 gauge wire for wiring, per unit. I'd be inclined with the current you are pulling to go use 20 or 18 ga to power the HDX units from the Main circuit, and make sure the wire gauge is heavy enough to cover what's being demanded from the Ducati VR. it's known to only be capable of perhaps 16 amp draw charging rate... Keep in mind, this is a motorcycle voltage regulator, it's not for running Skyview screens, lcds, back lights and cooling fan motors for each unit to keep the computer parts cool.


Can you turn the daytime brightness down on each of the HDX units and see if it draws less current?

Other than that, I am out of ideas. Is the wiring gauge from alternator to voltage regulator to the main buss and to the HDX units an adequate gauge? I know previous posters have stated, at least with the earlier Skyview 1000 Touch that the Rotax alternator couldn't run two panels.

Do you have Auto pilot turned on? Can you de active it or turn it off?

Look at pages 2.2 through 2.5, to calculate your current load. The Auto pilot and servos take a good chunk of juice.

https://dynonavionics.com/public_htm..._v15_2_002.pdf


Worst case, you might have to just settle for only one HDX unit in your bird, or get an additional alternator and Ducati VR to make enough voltage and current to keep up with demand.

Or yank the WiFi adapters?

Last edited by NinerBikes : 11-09-2019 at 01:06 AM.
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  #3  
Old 11-09-2019, 07:40 AM
MMiller MMiller is offline
 
Join Date: Oct 2010
Location: Babylon NY
Posts: 50
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If you have negative amps and declining voltage your system is not charging.

To troubleshoot the system we need to start here. With your meter on DC volts, what is the voltage at;
1) Regulator C pin
2) Regulator R pin
3) Regulator B+ pin
4) Battery positive post
Measure these voltages referenced to ground with the master switch ON and the engine stopped.
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  #4  
Old 11-09-2019, 10:11 AM
NinerBikes NinerBikes is offline
 
Join Date: Dec 2018
Location: Granada Hills
Posts: 305
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Also be sure to check that the spade connectors are tight on the voltage regulator.

They can get loose and need adjustment to "bite" the spade lug properly for continuity. Time and vibration can loosen them up.
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  #5  
Old 11-09-2019, 12:54 PM
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N804RV N804RV is offline
 
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Location: Mount Vernon, Wa
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I had a problem with another homebuilt and needed to figure out whether it was the idiot light or the voltage regulator. I rigged up a temporary digital voltmeter and went flying. I was looking for around 12.3vdc with alt switch off. And around 14.4vdc with the alternator on. Turned out the idiot light was correctly indicating an overvoltage condition with 15.5vdc on the battery bus under high RPMs. And, I had a failing voltage regulator.

Hope this gives you some ideas.
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  #6  
Old 11-09-2019, 02:43 PM
lon@carolon.net lon@carolon.net is offline
 
Join Date: Aug 2015
Location: Santa Monica, California
Posts: 86
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Quote:
Originally Posted by MMiller View Post
If you have negative amps and declining voltage your system is not charging.

To troubleshoot the system we need to start here. With your meter on DC volts, what is the voltage at;
1) Regulator C pin
2) Regulator R pin
3) Regulator B+ pin
4) Battery positive post
Measure these voltages referenced to ground with the master switch ON and the engine stopped.
With the engine off, the electric fuel pump off (i.e., the circuit breaker removed), and the avionics off, I got these readings on the multimeter:

With both Skyviews on and the Skyview showing 11.9 battery volts:
C 1.18 volts
R 11.9 volts
B+ 11.9 volts
Battery 11.94 volts

With only the pilot-side Skyview on (co-pilot-side off) and the Skyview showing 12.00 volts:
C 1.16 volts
R 11.98 volts
B+ 11.99 volts
Battery 12.00 volts

With the engine off, I also measured the resistance between the two yellow wires that plug into the G pins; and, after several moments of bouncing around, the multimeter showed a resistance of 0.2 ohms. There was no reading between each yellow wire and a ground.

With the engine off and the avionics off, the Skyview displayed these readings.
With the electric fuel pump off (i.e., the circuit breaker removed)
-4 amps with only the pilot-side Skyview on,
-5 amps with both Skyviews on,
-6 amps with both Skyviews on and the Dynon WiFi Adapters plugged.
With the electric fuel pump on (circuit breaker plugged in)
-7 amps with two displays on and the WiFi Adapters plugged in.
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Lon Sobel
Santa Monica, CA
RV-12, N58CV
VAF Dues Paid
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  #7  
Old 11-09-2019, 02:45 PM
lon@carolon.net lon@carolon.net is offline
 
Join Date: Aug 2015
Location: Santa Monica, California
Posts: 86
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Quote:
Originally Posted by NinerBikes View Post
Also be sure to check that the spade connectors are tight on the voltage regulator.

They can get loose and need adjustment to "bite" the spade lug properly for continuity. Time and vibration can loosen them up.
I watched my mechanic do this. He added one new connector, and tightened all of them very carefully.
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Lon Sobel
Santa Monica, CA
RV-12, N58CV
VAF Dues Paid
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  #8  
Old 11-09-2019, 02:46 PM
lon@carolon.net lon@carolon.net is offline
 
Join Date: Aug 2015
Location: Santa Monica, California
Posts: 86
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Quote:
Originally Posted by N804RV View Post
I had a problem with another homebuilt and needed to figure out whether it was the idiot light or the voltage regulator. I rigged up a temporary digital voltmeter and went flying. I was looking for around 12.3vdc with alt switch off. And around 14.4vdc with the alternator on. Turned out the idiot light was correctly indicating an overvoltage condition with 15.5vdc on the battery bus under high RPMs. And, I had a failing voltage regulator.

Hope this gives you some ideas.
I too had a failing voltage regulator, but my mechanic replaced it with a new one, and then replaced that one with another new one just in case the first was defective right out of the box.
__________________
Lon Sobel
Santa Monica, CA
RV-12, N58CV
VAF Dues Paid
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  #9  
Old 11-09-2019, 02:54 PM
lon@carolon.net lon@carolon.net is offline
 
Join Date: Aug 2015
Location: Santa Monica, California
Posts: 86
Default

Quote:
Originally Posted by NinerBikes View Post
I'm hazarding a guess here, but I believe you should try and disconnect one of the Dynon HDX screens completely, and just run one screen, and see what you get for Voltage and Amps.

Short of that, ask Dynon what the voltage and current draw is for each HDX unit., and what you have running in the backround.

The HDX, I believe is rated for up to 30V, on a 24V system, so current spikes doing damage is probably highly unlikely. However, the lower the voltage you run, the higher the current or amps you draw. You need at least 22 gauge wire for wiring, per unit. I'd be inclined with the current you are pulling to go use 20 or 18 ga to power the HDX units from the Main circuit, and make sure the wire gauge is heavy enough to cover what's being demanded from the Ducati VR. it's known to only be capable of perhaps 16 amp draw charging rate... Keep in mind, this is a motorcycle voltage regulator, it's not for running Skyview screens, lcds, back lights and cooling fan motors for each unit to keep the computer parts cool.


Can you turn the daytime brightness down on each of the HDX units and see if it draws less current?

Other than that, I am out of ideas. Is the wiring gauge from alternator to voltage regulator to the main buss and to the HDX units an adequate gauge? I know previous posters have stated, at least with the earlier Skyview 1000 Touch that the Rotax alternator couldn't run two panels.

Do you have Auto pilot turned on? Can you de active it or turn it off?

Look at pages 2.2 through 2.5, to calculate your current load. The Auto pilot and servos take a good chunk of juice.

https://dynonavionics.com/public_htm..._v15_2_002.pdf


Worst case, you might have to just settle for only one HDX unit in your bird, or get an additional alternator and Ducati VR to make enough voltage and current to keep up with demand.

Or yank the WiFi adapters?
All of these suggestions are good ones, especially for a newly-built plane that had electrical problems right from the start. However, my plane is a year and half old with 170 Hobbs hours, and it had no electrical problems until a few weeks ago. Also, the negative amp/declining voltage problem came on suddenly. The plane was perfect for a flight from Santa Monica to Torrance (about a half-hour of engine time, including taxi and run-up). The plane was on the ground, in the shade, at Torrance for 3 hours having vinyl tail numbers and an RV-12 vinyl logo applied. I was with the plane the entire time. No one turned it on or fiddled with it in any way. When I started the engine to return to Santa Monica, the engine fired up immediately and without hesitation; but the amps remained negative throughout my taxi and my run-up at 4000 rpm. And that's the way it's been ever since.
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Lon Sobel
Santa Monica, CA
RV-12, N58CV
VAF Dues Paid
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  #10  
Old 11-09-2019, 03:16 PM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,012
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The missing measurement here - the important one - is: What is the buss voltage with the engine running? If it is not over 14 volts then you have a charging system issue. If it is over 14 (but less than 15) volts then you have a display/measurement problem.
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