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  #1  
Old 03-03-2013, 11:31 AM
Bastien's Avatar
Bastien Bastien is offline
 
Join Date: Jun 2010
Location: Vannes, FRANCE
Posts: 149
Question Electrical issue=> I have symptoms but can't find the disease

For the last two flights I am having electrical issues on the transponder and radio noise with the right landing light…

The first time I experienced the transponder failure was last week in flight. The VP-X indicates “SHORT” and so the transponder line was shot down to preserve it.
I did a “RESET” on the transponder breaker through the Dynon skyveiw EMS page. It worked a few seconds and then indicated “SHORT”.

Today I tried to troubleshoot the problem on ground.

*With the battery ON and tranponder ON, everything is working well.
*With the battery ON, transponder ON and engine turning, everything is working well
*With the battery ON, transponder ON engine at idle RPM and alternator ON everything is working well.
*With the battery ON, transponder ON, engine turning over 1400RPM, alternator ON it fails (“SHORT” before it shorts, I read over 15A through the transponder on the VP-X page).
*With battery ON, alternator ON, engine turning without the transponder DB connector plugged in, I have no short circuit…

According to the Dynon, the alternator is working properly.

I removed the cowl and looked for a broken wire or something like that… Nothing
I plugged the “+12V” of my car to the alternator wire and ground to the ground. Start up the car and accelerate…. Nothing, transponder is working properly…

I did not remove the panel yet as it was a bit late in France and the temperature was getting below freezing.

I also have a symptom that is surely linked to the transponder failure. When I switch on the landing light (the right one) with the same conditions as above, I get a RX on the radio with a very high noise in the headset.

Ground problem?
Lose wire crimp?
Other?

I am getting out of ideas..


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Van's RV-8 3040 F-PVRB
Aerosport IO-375 turning WW200RV
Dual Dynon SV1000
SJ Wheel pants/plenum/cowl
Flying since 07/27/12

Van's RV-8 2513 F-PTGV
Lycoming IO-360 B1B
Purchased as a project--Finishing kit

Last edited by Bastien : 03-03-2013 at 11:36 AM.
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  #2  
Old 03-03-2013, 08:16 PM
BobTurner BobTurner is online now
 
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Location: Livermore, CA
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May be two different problems.
My guess is higher vibration at higher powers is causing an intermittent short to show up. I would look very carefully at the power wire from the VPX to the transponder. Look especially where it passes over or near any metal. You're looking for a tiny cut in the insulation which can cause a short; or, at either end, a stray strand of bare copper that can touch where it doesn't belong. You could try to simulate the engine running by powering the transponder on, engine off, and then shake and move the wire a reasonable amount by hand, see if you can induce the short to appear.
Unfortunately one of the most likely places for a stray bare wire to exist is at the transponder connector. It will be difficult to access there.
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  #3  
Old 03-04-2013, 10:12 AM
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Bastien Bastien is offline
 
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Hi Bob,
Thank you very much for your answer. I thought about it but when alternator is OFF whatever the RPM is , transponder is working properly. I tried to simulate the engine running by moving the power wire from the VP-X to the transponder but nothing..
I will try it again when I'll be back at the hangar.

I am really thinking about the alternator.
Is it possible to have a leak of current from the alternator itself ?
If my ground isn't a ground anymore but is +12V, it would explain the radio noise and why my transponder fails isn't it?
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Aerosport IO-375 turning WW200RV
Dual Dynon SV1000
SJ Wheel pants/plenum/cowl
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Van's RV-8 2513 F-PTGV
Lycoming IO-360 B1B
Purchased as a project--Finishing kit

Last edited by Bastien : 03-04-2013 at 10:15 AM.
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  #4  
Old 03-04-2013, 11:05 AM
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rleffler rleffler is offline
 
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I think I'm with Bob on this one.......

The fault should be isolated to the power wiring between the VP/X and the transponder.

Since the build is probably too new to have worn through the wire insulation, the next likely culprit is a bad crimp job in one of the connectors, most likely the one at the transponder. It's real easy to splinter off a couple strands of wire and not notice it when crimping. If one of these strands hits and adjacent pin or wire, you've got a short.

If the alternator was shorted, you would be seeing all kinds of other symptoms (i.e. smoke being released from the wires)

The Vertical Power guys are usually pretty quick to assist if you post to their support site. if the short error is only showing for the transponder pin on the VP/X, the problem has to be on that line.

bob
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  #5  
Old 03-04-2013, 12:16 PM
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Bastien Bastien is offline
 
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Bob,
Thank you for your answer. I visually checked the transponder side crimp yesterday and did not see anything. I will have a closer look at it in few days and inspect the VP-X side.
As recommended, I will write to vertical power support.
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Van's RV-8 2513 F-PTGV
Lycoming IO-360 B1B
Purchased as a project--Finishing kit
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  #6  
Old 03-04-2013, 12:52 PM
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rleffler rleffler is offline
 
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A few items to check........

Visual inspection looking for a stray wire stand is like looking for a needle in a haystack.

With the power off, using a ohm meter from the power pin on the transponder connector, see if there is any continuity to ground.

Another test would be to put the transponder out of the tray or disconnect the connector with the power and ground. What are the systems then? The VP/X should show it as open, not shorted.

I assume that you did visually check the pins in the connector and the tray to make sure that none are bent.

You may also want to consider asking a friend to check. Sometimes these types of issues are too difficult to find and will turn out to be something dumb and simple. People tend to do things consistantly, so you may be overlooking some key detail that a fresh pair of eyes may pick up.

Just suggestions......

bob
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  #7  
Old 03-04-2013, 02:39 PM
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MCA MCA is offline
 
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I'd recommend a fresh set of eyes on the problem as Bob suggests. This is an unusual set of circumstances which should not correlate with each other. So to me anyway the answer is not clear.

There is no correlation between the alternator and transponder circuits internal to the VP-X that would cause a short like you describe. Just to be safe, check that the secondary alternator is set to 'none' in the configurator. This won't cause a short if set incorrectly, but it is one more thing to confirm.

I suspect the problem is in the wiring or maybe the transponder. Put a 5A fuse in line with the male test pins (that came with your wiring harness) and connect that to the battery. Then plug in the male test pin into the transponder terminal in the wiring harness connector. See what happens (does transponder come on?), even wiggle some wires around to see if it causes the fuse to blow.


The noise issue is likely related to how the landing lights are wired. Recommend contacting the light manufacturer for guidance.
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  #8  
Old 03-04-2013, 02:55 PM
BobTurner BobTurner is online now
 
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I agree, most likely two problems. You did not say what type of landing lights you have. HD and high power LED's usually have switching circuits which can generate RF noise. If traditional incandescent lights then that would be unusual.
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  #9  
Old 03-05-2013, 08:04 AM
Grumpy-Hodge Grumpy-Hodge is offline
 
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Default Electrical Issue

Don't forget that the culprit could be internal to the transponder. Could be something loose inside the unit which is stimulated by vibration and causing a high current condition. If you had access to such, I would also put a dummy RF load on the transponder RF connection (antenna) to make certain that the RF output amp stage(s) aren't seeing a bad RF circuit to the antenna and thereby pulling a lot of current until the EMS trips the breaker.

Good luck!
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  #10  
Old 03-05-2013, 08:14 AM
pilot2512 pilot2512 is offline
 
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Just a thought, but you may want to check output of alternator with a meter set to read ac. May have a diode going bad putting out to much ac and the transponder may be more sensitive to it.

Jay
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