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wrongway john

Well Known Member
Just have basic VFR, and was using Garmin 696, two battery powered headsets, the usual radio, transponder and strobe, I guess that?s it.

Today, my low amp warning kept coming on about every 3-5 minutes. My volts were fine, over 14.2 or so, so it seems alternator is charging okay, but amps would steady to 9-11 or so, then drop down to about 1-3 before climbing back up. It did this about four or five times.

I've flow this plane about 80 hours thus far, and no problems like this before.
Any leads on where to go from here and what to check? Any help always appreciated.
 
How was your voltage during those period of low amp reading?

It could be simply a bad amp meter.
 
Not completely certain, but I believe the volts were still at 14.2 or so when the amps were down, I'll pay more attention on my next flight up.

My amp meter is a part of my VM-1000 glass display.
 
Next time you see the low amps, turn on the landing and taxi lights and watch the voltage. If the amps stay low and the voltage starts to decline it could be an early sign that the voltage regulator is on its way to failing.
 
Where are you sensing the amps?

If it is the battery line only, it is possible, and reasonable, to get low amps when the battery is fully charged...

The voltage reading would be a good indicator.
 
I had the same indication on a MGL unit. It turned out to be a cold solder joint on the Hall effect current pick up. Check all your connections.
 
Fixin' to head back across the street. I'll do Neal's test first, then check the connections next. Gil, I'm not sure, just going off the readings off my glass display. I haven't charged the battery are done anything special to any of it lately. Kept hearing the warning beeps, displaing low amps, and sure enough it was down to just 1-3 or so, then climb back up to 6, 7 or so, then up to 11, where it would slowly start going back down again. I'm going to get some more accurate data with amps and voltage right now. Maybe this will tell me something.

I appreciate all the feedback so far everybody.
 
Got back from a 40 minute flight. Don?t know if these give any new clues, but volts were nearly always consistent at 14.4. When I turned on all of the nav lights, strobe, landing light, it dropped to 14.1, while amps shot up another 10 amps or so. Low amp warning never went off this time, but still dropped down to 4, and with just the basics on, showed all kinds of readings generally from 4-10 amps, while shooting up another 10 amps when pretty much everything was on. Amps seem to be all over the place, naturally they go up when I start turning things on, but if I?m not, should they be jumping around that much?
 
Master switch

I had a similar problem on my Dynon EMS D10.
Turned out to be a bad crimp connector on the avionics master switch.
Mine was a spade type. Yours may be the screw type.
They looked good but re-crimped them anyway and problem fixed.
Best
 
The regulator responds to bus voltage by sending more current to the field winding of the alternator when the bus voltage drops slightly, and backing off when the voltage rises. If the regulator is more sensitive to voltage variance than the Dynon sensor, then it's entirely possible that the bus voltage may be going up/down by 50 millivolts or more and this is enough to trigger the regulator to put out more current back to the battery, but not enough to show up as a 0.1 volt (100 millivolt) difference on the Skyview.

At low amperage system draw (nearly everything turned off) it's very possible for the regulator to see everything "fully charged" on the battery with only a small load and basically be putting out almost nothing, and then as the battery slowly depletes it finally reaches a threshold where it starts putting current to the field - but that threshold is too small for Dynon to see. The result is that you see current variations without voltage variations.
 
Sounds like an amp meter indication problem to me, if the volts are stable and read as you say, the alternator is doing it's job on maintaining bus voltage.
 
az_gila said:
Does your instrument show + and - directions for the amps?
Click to expand...

Not, none of that, Gil, just shows the numbers.

Walt, the amp meter which is in a VM-1000 glass display seems to read like it supposed to when I flip things on and off.

Thanks everyone, you guys have helped me at least eliminate the alternator. One suggested the master switch, and I read from the archives where this turned out to be the problem too. Might be worth a try, but as I was saying, last 40 minute trip up, the low amp warning didn?t go off. I?ll keep an eye on it, and if it comes back again soon, I?ll start with replacing the master switch, and see if that puts a stop to it.
 
It still could be the alternator, assuming the VM1000 is wired correctly, or it could be the regulator telling the alternator to produce less amps too early...

From the VM1000 manual - my adding of bold -

1.8 ELECTRICAL MONITORING SYSTEM OPERATION
VOLTAGE is displayed both graphically and digitally. Full color range marks provide a quick reference for fast analysis of voltage levels. As voltage rises, the graph size increases proportionately.
Additionally your system has a built-in warning system that flashes the graph when system voltage is out of nominal range (either too low or too high) .
AMPERAGE is displayed both graphically and digitally. Full color range marks provide a quick reference for fast analysis of amperage levels. As amperage rises, the graph size increases proportionately.
The digital readout displays amperage at 1 amp resolution. This is useful for troubleshooting.
The amp system functions as an 'alternator load meter' displaying current flow FROM the alternator TO the aircraft electrical system allowing you to see if a load (such as pitot heat) is really drawing current when turned on. You should see an increase on the amp display when you turn on a load, such as pitot heat for example. This tells you that the pitot heater is drawing power and is probably OK. By verifying that voltage remains the same, then it can be assumed that the alternator is supporting the additional load. A very handy feature for in-flight testing / verification of electrical loads and the alternator charging system.
Additionally your system has a built-in warning that flashes the graph and triggers the audio/visual annunciator system (if installed) when the alternator does not produce power for the electrical system. This occurs at low amperage levels of approximately less than 2 amps.
 
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az_gila said:
It still could be the alternator, assuming the VM1000 is wired correctly, or it could be the regulator telling the alternator to produce less amps too early...

[/I]
Click to expand...

If the bus voltage is being maintained, then the alternator is suppling sufficient current (amps) to carry the load.

If the alternator can't carry the load (not producing the required current) then bus voltage will drop (14.1V means the alt is carrying the load).

If I could only have one meter I would have a voltmeter, it provides the "critical" information which is bus voltage.
 
Man, you guys are good. Gil, thanks for digging that out for me, I'll study my VM1000 manual some more. Walt, yes, when everything was on, my voltage dropped to 14.1. Otherwise it stayed mostly at 14.4 when I had a lighter load.

I'm not sure what master switches Van's uses now. Seems like at my last annual, those guys had trouble finding another particular switch that was in that same bank, and said they were an older set. These are the original white ones that were put on in '98, I believe, and I'm fairly sure came from Van's. Anybody know if these are still readily available? I'll send a pic if needed.
 
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