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  #11  
Old 08-27-2018, 12:30 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
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Plus component tolerance drift in the vpx and/or the transponder. None of us have any way of knowing how close to the edge the vpx was operating for those years.
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  #12  
Old 08-27-2018, 01:42 PM
spatsch spatsch is offline
 
Join Date: Nov 2014
Location: Randolph, NJ
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Quote:
Originally Posted by rv7charlie View Post
Plus component tolerance drift in the vpx and/or the transponder. None of us have any way of knowing how close to the edge the vpx was operating for those years.
OK you convinced me. So I figured I will perform the following tasks in that order when I head back out to the airport:

1. Reproduce the fault and fault behavior -- make sure I didn't overlook something I should have noticed or noticed something that was a coincidence leading me in the wrong direction.
2. Check the Alternator wires and belt tension and general condition. -- easy to do and most people which responded public or private were voting for the alternator.
2. Increase fuse limit from 3 to 5 A on the VP-X. This would be the easiest fix as nothing is really broken... . Components just drifted a bit which is normal.
3. Replace the EarthX with my old battery. I got some private communication that indicates that the EarthX protective circuit could cause issues and it's easy to do as I still have the old battery takes 5min to switch.
4. Replace alternator -- I don't have a spare one so unless I find one I have to spend some $$. That's why I ranked it last even though most people are rooting for that one ... .

Thx

Oliver
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  #13  
Old 08-27-2018, 03:25 PM
rv7charlie rv7charlie is offline
 
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Location: Pocahontas MS
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If your efis has data logging, look at the system voltage track over the period you've been having the overcurrent notices. If the alternator is going out of spec, you should see it in the history, even if the alarm set points are wide enough to hide it in real time.

If it were my system and everything is *functioning* correctly (voltage within limits, xponder works properly), I'd be betting on instrumentation error over any actual defects in the system.

Do you get to set the 'trip point' in that vpx circuit yourself? If so, how about bumping it up to 5 amps & see if you still get the alert.
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  #14  
Old 08-27-2018, 07:21 PM
spatsch spatsch is offline
 
Join Date: Nov 2014
Location: Randolph, NJ
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Quote:
Originally Posted by rv7charlie View Post
If your efis has data logging, look at the system voltage track over the period you've been having the overcurrent notices. If the alternator is going out of spec, you should see it in the history, even if the alarm set points are wide enough to hide it in real time.

If it were my system and everything is *functioning* correctly (voltage within limits, xponder works properly), I'd be betting on instrumentation error over any actual defects in the system.

Do you get to set the 'trip point' in that vpx circuit yourself? If so, how about bumping it up to 5 amps & see if you still get the alert.
OK I owe you a beer or something.

Went to the airport after work. I could reproduce the issue now reliably:

1. Switch alternator off to let battery drain a bit.
2. Switch alternator on -- transponder triggers as short
3. Wait till alternator load < 10A reset transponder everything works

Then I followed you advice and bumped the fuse value to 5A. Tried to trigger the short again on the ground and couldn't. Went flying and tried different things to trigger it and couldn't.

So that does seem to have solved the issue. Still baffled by the fact that it worked flawless for 4 years at a 3A setting... . What's the odds..... .

Oliver
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  #15  
Old 08-27-2018, 07:48 PM
rv7charlie rv7charlie is offline
 
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Glad you could solve it without injecting money. :-)

If you have data history from the efis, I'd still check the system voltage history. If the regulator's set point is drifting upward slightly, that could account for the change in behavior. Again, if the vpx trip point was very close to actual current over the prior years, even a very slight uptick in system voltage (even if well within normal range) could drive current up slightly, causing the current detection to fire.
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