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Tricky Electrical Issue - Need advice

PaulKRV7A

I'm New Here
Fellow RVers,
I have a RV-7A with Titan IOX-360, Plane Power alternator (with internal volt reg), VPX (Vert Power sport) and dual Dynon Skyview Classic. For some time now I've been experiencing fluctuating and high ammeter readings on the Skyview EMS (jump from normal to 90+ Amps) anytime I fly. At first I was quick to land but after replacing the alternator, checking all wiring for loose connections, and replacing the battery (PC 680) I am still having the same issue. This only occurs once the engine is warmed up (happened much less in winter when temps were cooler) so I suspect maybe the voltage reg or one of the shunts is overheating and causing the faulty readings. There has been zero signs of damage due to high amperage on any wires, battery, etc and I even had the old alternator bench tested and both it and the volt reg checked out fine (so now I have a spare...). I am considering making a hole in the front left intake air ramp and running a hose to put air directly onto the voltage regulator to cool it...I have seen others do this but I'm still shooting in the dark and was hoping this sage and experienced group might offer thoughts, experiences to help. TIA! and pictures attached.
 

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It's unlikely that the Plane Power alternator puts out 90A. When it does put out around 60A, the bus voltage will sag close to 13.6V. That's how you know the alternator can't keep up with the demand.
Lithium batteries load the alternator for a short time after startup (a lot more than the Odyssey does) but I haven't seen more than 63A coming from the PP alternator on my airplane.

Check your shunt connections or shunt type setting in your Efis. May just be a configuration issue.

Lenny
 
My Dynon 180 also used a shunt and did same as what you' re describing with amps spiking BUT no voltage swing as one would expect. Turned out the signal wire on the shunt had bad, ie loose connection on a crimp. Signal wire pulled loose on inspection. Replaced connector and all was well. But I also have a spare internal regulated alternator there on the shelf..as result of poor troubleshooting !!!! If it had been a voltage regulator problem and the amps had been real , the voltage would also spike.
 
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My Dynon 180 also used a shunt and did same as what you' re describing with amps spiking BUT no voltage swing as one would expect. Turned out the signal wire on the shunt had bad, ie loose connection on a crimp. Signal wire pulled loose on inspection. Replaced connector and all was well. But I also have a spare internal regulated alternator there on the shelf..as result of poor troubleshooting !!!! If it had been a voltage regulator the voltage would also spike.

+1 on this. A loose connection on the shunt sense wires will give erratic current readings. There should be fusible links or fuses in series with each sense wire, so check those for integrity as well.

V
 
+2

While a bad connection or wire is much higher on the list, a failing shunt could cause this as well. Some use solder for the primary shunt plates and a mfg defect could allow vibration to work the plate loose, increasing resistance.

Larry
 
Welcome to VAF

Paul, welcome aboard the good ship VAF. :D

Gotta agree with above statements, problem is most likely from the sensor, not the alternator.
 
While I would normally agree on it being a sensor issue, I had an identical problem with my PP FS-14B alternator, amps and volts 'hunting' under a light electrical load on an identical system, SkyView Classic, VP-X Sport, but with a lithium battery. Operation immediately after start when charging at higher currents (20A+) was normal. I did find a bit of heat damage (almost arc like) to one of the alternator plug pins but after cleaning that and reinstalling it, couldn't find anything else no matter how hard I looked. In the end, I replaced the alternator with a B&C unit on the vacuum pad and their external voltage regulator, and that has solved the issue.

You can see the issue in this youtube video.
 
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Paul, in addition to the above comments, I'd recommend routing the cooling hose directly into the thin heat shield in the back. It can easily be removed and a hole drilled to accommodate the hose.
 

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Amps reading high

Paul - what does your AMPS widget read in the 30 sec shutdown cycle ?
Maybe we have the same fault if yours also shows a really high Negative amps Like mine , which is impossible in real ops - if so then I’m figuring we both have a bad EMS module.
 
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Almost certain your alternator is not putting out 90A!
Your ammeter is likely to be a voltmeter measuring volts drop across the shunt resistor. As the shunt resistance is low so is the measured voltage. Any poor connection between the shunt and the "ammeter" (voltmeter) will increase the resistance, and so the measured volts drop, which will be displayed as a large increase in output current.
Check the connections between the shunt and the Skyview.
There is also a small possibility of a fault inside the Skyview.
Pete
 
Maybe you could use this as a trouble shooting tool:
Bayite BYT-VAM-033. $19 on Amazon

Even better would be a Fluke type ammeter with Min-Max recording.
DC of course

Paul Reeder
RV-7A Central Ohio
 
Shut down cycle normal

Jake,

Once back on the ground at idle the ammeter tends to provide normal indications and I do not see negative amperage, so you might be experiencing a different issue. I ordered a new shunt, and have checked all crimps for bad connections. I’m hoping the new shunt will fix my issue. I appreciate all the comments and help!

Cheers,
Paul
 
FWIW a shunt is just a "calibrated" hunk of wire. An "ammeter" is just a voltmeter that reads the extremely small voltage (millivolts) across the shunt. A tiny change on the ammeter leads, like corrosion or even just a slightly loose wire, will make huge ammeter swings. If at idle everything is normal, that indicates engine vibration is causing a wire to temporarily disconnect.

If the current reads negative then the culprit is a bad connection somewhere in the wiring to the ammeter not the shunt. It is impossible for negative current to happen in our aircraft. Your panel can not generate current to power your alternator which is what negative current means. If it was a main shunt connection problem then your panel voltage would go crazy and possibly some avionics would shut down/recycle, which isn't happening.

Just my 2 cents.

:cool:
 
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It is impossible for negative current to happen in our aircraft. Your panel can not generate current to power your alternator which is what negative current means. If it was a main shunt connection problem then your panel voltage would go crazy and possibly some avionics would shut down/recycle, which isn't happening.

Just my 2 cents.

:cool:

This only applies if the shunt is installed between the alt and main bus. If the shunt is installed between the battery and the bus, as some builders do, it would not apply. In that case polarity determines the direction of current into or out of the battery. In these installations, negative current points to the alternator ceasing to provide output or at least dropping output below the system load.

I don't believe the OP has told us where his shunt is installed.

Larry
 
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