alternator or voltage regulator problem

[oynif]

I have wired my EIS tach lead to one of the two output wires coming from the alternator where it connects to the voltage regulator.
The output from the voltage regulator to the the battery is led thru a 20A C/B.
My EIS tach readings started to be extremly erratic and ended up showing 0 as the C/B popped.( all this on ground trying to tune the aerocarb )
How do I find the fault , is there any way to measure for correct function of the two items ?
The easiest part to exchange is the voltage regulator, where do I find a replacement, is it used on another vehicle that would make it easier to find locally ?

Thanks
Kurt Nielsen
Babylakes/Aerovee

[tonyr]

Hi Kurt,

Sounds like you have 2 problems.

Erratic tach reading, which may be a problem with the input from the alternator being too "noisy" electrically. This may be a simple fix by changing the tach input to the other lead and/or installing a resistor in the line. Usually the EIS manufacturer will give guidance on the resistance value. A dynon D180 uses around a 27-33Kohm resistor.


The other issue is the current draw from the regulator,which I'm assuming goes to the battery then tomaster sw/relay to the sub-circuits like avionics lights etc..
This could be a discharged battery, wiring fault, faulty regulator, faulty C/B or some other faulty component in the system.
Also there have been reported problems with LiPo type batteries causing main C/B's to trip if you have one of those. I think there was a post recently where one builder changed out a 20A CB for a 30A CB in a LiPo battery installation.
When the CB trips, the tach loses its power, so that's why I think there are two problems.

You would need to do some voltage measuring and isolation fault finding to narrow down what it might be.
i.e. check battery voltage, no charge, with nothing else turned on. Turn on stuff see what happens to the voltage.
Measure the current draw from the battery and so on.
Fire up the engine to fast idle check the battery voltage, and current draw with nothing turned on.. and so on, a bit of work to narrow down before changing things willy-nilly.

Cheers
Tony

[oynif]

The tach reading was steady and correct shortly before the C/B tripped. Battery was recharged and engine started again with
same indications as before.
When reversing the input wires from the alternator C/B tripped instantly ( engine running ).
I removed the voltage regulator from the aircraft and connected a battery charger to the regulator and a battery and it seemed to Work normally.
The alternator is now the prime suspect, Iwill try to connect a voltmeter( and nothing else ) directly to
the output wires from the alternator, engine running ,
even though I am not sure what it should read.

All inputs welcome
Kurt

[tonyr]

"When reversing the input wires from the alternator C/B tripped instantly ( engine running )."

I'm not surprised that happened.. I would have done it engine off!

Not sure how you used a battery charger to test the regulator as it would expect an AC input to convert to DC for the battery?

The no load voltage from the alternator will be quite high, maybe as high as 40vAC, dropping to maybe 20vAC under load.

I would have thought the aerovee manual would give you some specs to check the alternator against.
There should be a resistance value from alternator lead to lead. Infinite resistance from an alternator lead to engine case or alternator frame.
May even have the ac volts outputs at x rpm? It should also have the volts DC output for the regulator at x rpm.

I would use a megohmmeter or insulation tester to check the windings to frame. A good digital voltmeter to check the internal resistance of the windings, regulator DC output and alternator AC output

Do you have local EAAers that could help out?

PS A guy with a Jabiru engine had a similar issue with the main C\B tripping. He found that his main earth lead to airframe was loose and slightly corroded. A cleanup and re-torque of the earth stud fixed the issue.. might be something else to look at?

[oynif]

The alternator failed because the trigger shaft assembly flat head screws had worked completely loose and fauled the alternator stators.
The ring with the magnets ( installed when recieved in the kit) was also Loose, all screws loose ,but still in place , one screw broken as can be seen in the picture.
The trigger shaft was installed according to the manual with locktite on the screws.

I was fortunate that this happened on ground.


Kurt Nielsen
Aerovee# 296

IMG_2041b.jpg (32.66 KiB) Viewed 4504 times

[kmacht]

Were they 5/8" long patched screws or the non patched 1/2" long screws? There was a service bulletin out for aerovees 2012 and earlier for this exact issue.

Keith
#554

[tonyr]

About all I can say is : "EXPLETIVE" !

So as the screws were progressively backing out they were buggering the windings, so the CB tripped.. until it failed completely
The insulation check would have indicated the shorted windings, may have saved a complete failure but it would have been same cost to fix I expect

[oynif]

Keith
My aerovee is no296 ie 10a alternator and thus not covered by the bulletin.
Kurt