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Alternator Noise

jimluper

By jimluper
in Vintage Mooneys (pre-J models)

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jimluper Contributor

jimluper

Posted
Posted

What brand alternator to buy?

2 years and 4 months ago, I replaced the alternator and regulator in my 1975 E model with a solid state regulator and a "Plane Power" alternator.

Notice I said 2 years and 4 months. That is 4 months out of warranty and the noise (ac ripple) coming out of that thing is something terrible. Called Plane Power and they suggested a capacitor on the output. That didn't work. The whining noise in my headset made me shut down the electric bus after touchdown yesterday.

Now the fact that I have to buy another alternator is just accepted.

However, my question is what brand. I am not sure that I want to put another "Plane Power" alternator back on the bird.

Any suggestions?

Thanks, Jim

DXB Grand Master

DXB

Posted
Posted

This may be a dumb question, but if you have an audio panel with an "isolate" setting, did you try that? Or turning the audio panel off altogether?  Or if that doesnt work, pulling  individual breakers for non-audio components to localize the source?   It could be a ground issue that's not with the alternator itself.  This was a huge problem for me before I redid the crappy audio wiring when redoing my panel.  Even after that, I had interference from my ipad charger that resolved by adding ferrite filters on the cable.

carusoam Grand Master

carusoam

Posted
Posted

I would think there would be a significant number of similar observations if the plane power unit croaked shortly after the warranty expired.  There are many people here that are moving in that direction.  Same thing if you VC is a Zeftronics unit.

I would be wanting to hunt down where the noise is really coming from first prior to swapping out an unworn unit...

A few places have been recently ID'd for unexpected electronic noise and or interference of some sort...

- a JPI instrument, breaking squelch...

- portable things plugged into the cigarette outlet like cell phones and other battery powered devices trying to recharge their batteries....

- wiring and connectors related to alternator...susceptible to breaking and/or corroding in a high vibration environment...

Some ideas I think I remember by reading a lot of threads,

-a-

N201MKTurbo Grand Master

N201MKTurbo

Posted
Posted

I have found that when an alternator starts to whine, it has lost one of its six diodes. This causes a hole in the normally smooth output waveform. There are six diodes each responsible for conducting one half of each of the three phases. 

The regulator will compensate for the loss of output so it appears to be working normally except for the whine. 

The diodes rarely fail themselves, but the vibrations of the engine will cause the solder joints that hold the diodes in place to fracture. I have been able to resolder them in most cases. Most alternator shops will just replace the whole diode assembly, which ironically takes more soldering then just fixing the fractured joint. 

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N201MKTurbo Grand Master

N201MKTurbo

Posted
Posted

I have never disassembled a Plane Power (Nippon Denso) alternator. I just looked at some pictures and it looks like the cover on the back would expose the diode assembly. If not then you usually have to remove the back half of the case. This is easy, just remove the screws holding the case halves together, give it a few love taps with a rubber mallet and it should slide apart. To replace the back half you need to hold the brushes back this is done by pushing them back into their holder and inserting a stiff wire like a piece of coat hanger into the small hole by the brushes. After sliding the case halves back together,  pull the wire out and the brushes will extend and contact the slip rings.

Soldering the diodes or the stator wires takes good soldering skills with big wires. You will need a very powerful soldering iron like a Weller gun or a soldering tip on a burns-o-matic torch.

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N201MKTurbo Grand Master

N201MKTurbo

Posted
Posted

This looks pretty close to the Plane Power alternator. Unlike the Prestolite  alternator, it looks like the diode assembly is not repairable. But it can be replaced without soldering.

If you remove the rectifier assembly and take it to NAPA they can probably match it up.

This is definitely a job for the hangar fairies. It is not legal in any form. Re-soldering a fractured diode is just a repair and would be legal, but replacing a part with and automotive replacement would not. That being said, it would be better then it is now.

https://www.youtube.com/watch?v=CImyX5KuGvQ

If this is the same alternator, it would be worth a try to just remove and replace the same rectifier assembly. It might just be a loose connection on one of the three Phillips screws that connect the stator windings.

 

jetdriven Grand Master

jetdriven

Posted
Posted

The AL-12P70 Plane power uses a proprietary rectifier and it is not possible to find one. The Suzuki Samurai alternator is internally regulated, which is different.  I know this because my rectifier went bad and I spent half a day taking it apart tryin to find one. 

Hartzel, (Kelly) said just buy a new one.  Another good brand bites the dust. 

Fly By Night Contributor

Fly By Night

Posted
Posted

I just finished a troubleshoot and repair of a Plane Power AL 12-P70 alternator on our Mooney.  I spent alot of time troubleshooting a whine which was coming from the alternator which was 2 1/2 years old.  I removed the unit, took it to a local Alternator shop, they put it on an Oscilliscope and noted the AC waveform, ordered and replaced the rectifier which was an 8 diode unit, I installed  the unit and it now works fine with no whine, total cost, 20 dollars for the rectifier and 60 dollars for the labor.  It was a denso unit.  A pretty abysmal MTBF in my opinion.

Fly By Night Contributor

Fly By Night

Posted
Posted

From my receipt, the part is . RECT ND 8 DIODE 60-80A IR/ IF 118mm OD Stator.  I don't see an actual part number nor do I know where it was obtained, but it seems to me that any electrical shop worth its salt should be able to find one.  

By the way, I called Hartzell and told them about my experience and asked if they were interested in receiving the defective Rectifier, but they weren't very interested, so I tossed it.  

Guillaume Collaborator

Guillaume

Posted
Posted (edited)
On 26/12/2015 at 4:24 PM, jimluper said:

What brand alternator to buy?

2 years and 4 months ago, I replaced the alternator and regulator in my 1975 E model with a solid state regulator and a "Plane Power" alternator.

Notice I said 2 years and 4 months. That is 4 months out of warranty and the noise (ac ripple) coming out of that thing is something terrible. Called Plane Power and they suggested a capacitor on the output. That didn't work. The whining noise in my headset made me shut down the electric bus after touchdown yesterday.

Now the fact that I have to buy another alternator is just accepted.

However, my question is what brand. I am not sure that I want to put another "Plane Power" alternator back on the bird.

Any suggestions?

Thanks, Jim

The exact same issue happened to me 9 months ago. See http://mooneyspace.com/topic/14907-beware-of-plane-power-alternator/ ...

Plane-power finally sent me a new AL12P70.

I opened the faulty alternator and found the opened diode.

Edited by Guillaume
  • 5 months later...
jetdriven Grand Master

jetdriven

Posted
Posted (edited)
On 12/27/2015 at 1:10 PM, N201MKTurbo said:

Without taking one apart, this would be my best guess for the replacement.

http://www.maniacelectricmotors.com/100mm-alternator-rectifier-denso-60-80-amp-8mm-post-inr720xhd.html

 

the PP unit has a 6mm output post. I am guessing it is this one, and I think Im gonna order one to see. http://www.aspwholesale.com/rectifier-nd-p1359.html

 

To do a dynamic functional test of the rectifier assembly, put a digital volt-omh-meter on the outpost when the engine is running. Ground the other lead.  Set the DVOM to AC volts and and you are looking for no more than 1 volt AC, preferrably less than .5 or .2 but I have a feeling these units are fairly on the noisy side for aircraft so maybe < 1 VAC is all you'll get.  You can also check the individual diodes with the ohm meter.  continuity in one direction, open circuit in the other.

 

my problem is  constant whine which increases in volume with higher load on the alternator, the pitch seems constant. with enough load, such as all lights on, the stormscope WX-1000 inhibits. pulling the alternaotr field breaker kills the whine and immediately brings back the sotrmscope.  SO I think its AC in the skin, freaking the Stormscope out.  Reading these articles, makes me think its the regulator, however,  because the pitch doesnt change with RPM..  I have the original OECO or electrodelta mechanical voltage regulators.   http://www.eham.net/articles/15113      http://www.avweb.com/news/maint/182896-1.html

 

I did clean the battery terminals, no corrosion and no improvement.  I also have an Aera 500 wiht the flying lead cable plugged into the audio panel, perhaps its a ground loop whine but that doesnt explaint the SS acting up.

Edited by jetdriven
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jetdriven Grand Master

jetdriven

Posted
Posted

It's completely repeatable with pulling the field wire. Resetting it causes the stormscope to inhibit.  It's not P-static.  It's solely related to alternator load.

N601RX Grand Master

N601RX

Posted
Posted

If its related to load and not RPM then it could be from the brushes arcing more under higher field current or coming from the regulator.  If you need a regulator the Plane Power regulator seems to be a very good unit, I've had one for 4 years and its been very stable.

A full bridge 3Phase rectifier with a peak voltage out of 14.1 will have about 1.97VAC P-P riding on it. It will be up to the RC constant of the battery/wiring to filter it from there. With the loss of a single diode the P-P voltage will become around 7VAC.

jetdriven Grand Master

jetdriven

Posted
Posted

Correction, the pitch increases with RPM and the amplitude increases with load.  Which suggests the rectifier.  In 3 days the new one comes in to settle this once and for all. 

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