Don't throw away your Generator!

[moodychief]

I discovered something that I felt other mooniacs need to try before replacing their generator.  I have a '63 C model with a Delco Remy generator and Delco Remy voltage regulator on the firewall.  When I bought my Mooney there was an extensive pre-buy and annual performed on her since she was over 6 months out of annual.  A brand new battery had been installed.  Two months (and 20 hrs) later I was having problem with the battery keeping a charge.  Most of my flights were during the day so any slow battery drain was not noticeable.  The maintenance shop thought it was a bad battery and replaced it under warranty.  Several weeks later I noticed the same problem and took my plane back to the shop.  They tested the generator and said it needed to be replaced.  I didn't have a problem replacing it as it had over 800 hrs on it.

Fast forward to 2010.  My plane went in for an annual and was grounded for three weeks while waiting for exhaust rebuild.  Six weeks after picking it up from the annual I was doing a quick night flight for a VOR check.  When I turned on the landing light I noticed immediately I was running on battery.  As soon as I got to the hangar I put the battery on the charger and was down to 20%.  This meant I had been draining my battery over several flights.  Upon looking at my ammeter I noticed it wasn't zeroing out when the power was off.

Calling on local mechanics, I couldn't find ANYONE with extensive generator experience as they all said it sounded like it needed replaced.  I finally found someone willing to come out and help me troubleshoot even though his generator experience was limited to a Harley Davidson.  During troubleshooting we started at the electrical bus and worked towards the generator.  Everything checked out so it was determined it was the generator.

Not convinced that my generator with 250 hours had gone bad, i asked the mechanic if we could hook a meter to tell if the generator was putting out anything before deciding to replace it.  I also suggested we try to polarize it since we didn't have anything to loose and several labor hours and a generator to gain.  Neither of us knew if you had to flash it while the engine was running or not.  We flashed it without the engine running and started it up.  The meter was showing some voltage but the longer the engine ran the weaker the voltage reading was.  When I gave him a thumbs down, the mechanic carefully made his way to the firewall and flashed the regulator again.  EUREKA!!!!  Immediately the meter jumped to 13.89 volts.  I tried several settings and was even getting 14 volts at 1400 rpm.  I shut it down and restarted to make sure it wasn't a fluke and got the same results.  Went the next day and did extensive run-up with everything turned on and was getting EXCELLENT voltage!

Today I made a 4 hour round trip to Saint Louis and was 10-20 amps on the ammeter the entire trip. 

LESSONS LEARNED:  1)  Old mechanics that know all about generators are hard to find;  2)  Pay attention to what your ammeter reads when no power is going through it; 3) Be involved in the troubleshooting...you may ask a question that results in trying something different that resolves the situation; 4)If you can't find an old, knowledgeable mechanic, find a younger one that is willing to listen and learn with you.  I never would have been able to save my generator without his troubleshooting skills and willingness to approach the front-end of an airplane with the engine running.  5)  Length of time at annual or something done at annual (maybe momentarily disconnecting battery) can depolarize your generator.  Although mine was putting out voltage it was only enough to allow a slow draining of the battery.

Sorry for telling this long story but hopefully it will help at least one Mooniac in saving money and downtime.

 

[piperpainter]

I ditched the generator a year ago and not only did I get a 70Amp alternator I lost 7 or so lbs on my aircraft empty weight. Also I save gas because as I am taxiing or before I shut down I don't have to run it up to above 1400 to get a quick charge. Plane Power is awesome! Good story otherwise!

[moodychief]

Piperpainter,

I have heard great things about alternators.  I'm glad your experiences are positive.

m hangared at a GA airport where there is no long taxi times.  Before shut-down, I usually run 1700 rpms for a couple of minutes with mixture leaned to reduce any chance of carbon build-up on the plugs.  I basically kill two birds with one stone.  When this generator needs replaced I may look at an alternator.  Right now, why spend the money if you don't have to.

 

 

[jpusser]

I have the delco gen with the zeptronics regulator.  I have also had dead battery issues and weak battery.  I also have a problem with the generator breaker poping.  I believe it is because the battery gets low.  While flying the garmin 496 will go into spells of low voltage.  The genetator has receently been rebuilt according to logs.  How do you flash generator.

[thinwing]

Moodychief...I gotta admit than when i read about "flashing"and repolarizing your generator ,I thought this is pure science fiction!!!As a matter of fact I still do...I have never heard of anybody "flashing" their generator/voltage regulator before...can you please explain this all again??Inquiring minds are curious..kpc

[MooneyMitch]

Hi Kelly. 

Lots of info. on the internet regarding "flashing" [polarization] of Generators.    The following explanation seems correct.

Generators need some magnetism to get started. This "residual" magnetism remains in the Field pole pieces even after the engine has stopped.

The next time the generator starts up, the residual magnetism creates a small voltage in the Armature windings.   Not enough to charge the battery, but enough to allow the Field windings to draw current. As the Field current increases, the pole pieces create even more magnetism.  That makes even more voltage in the Armature, and the cycle continues until the
generator is capable of producing maximum output.

What happens though to a generator which has been stored a long time or is freshly built?   The residual magnetism may have decreased to the point where it can no longer get the generator started producing voltage.   In the case of a new generator or one which has been mis-treated, the residual may even be of the wrong direction (North and South poles reversed).

Polarization ["FLASHING"] is a simple process used to restore the Field pole residual magnetism and ensure the magnetic direction is correct.

Regulators do not require flashing or polarization.

Take care. 

[moodychief]

To polarize the generator, take the cover off the voltage regulator.  There are three terminals:  Battery, Generator (or Armature) and field.  To polarize, start the engine and take a jumper wire to touch the Battery and Generator terminals creating a brief spark.  This will polarize the generator.  When we flashed mine, the output went from about 1 volt to 13.89 volts instantaneously.  I did extensive testing with different power settings on the ground before embarking on my trip to St. Louis (from Little Rock) and was seeing from 13.4 to 14.5 volts starting at 1400 rpms.   

[MooneyMitch]

There is no disrespect meant for any previous posts on this subject. 

However, per the Zeftronics web site, the polarize method in their trouble shooting section states that the engine is shut off and the GCU [voltage regulator] is to be disconnected from the generator.  In my opinion, this would be a much safer situation.  This method has worked for me.

Happy Mooney [w/generator] flying!

 

 

[moodychief]

I have the old mechanical Delco Remy voltage regulator.  We tried flashing it before starting the engine with no success.  That is when we decided to try it with the engine running.  I agree about the safety.  That is why I let the A&P do the flashing while I was in the cockpit on the controls.

 

[MooneyMitch]

Ok, in this situation, it would fall under the "whatever works" method.  Glad all is well and you are safe. 

[moodychief]

Mitch,

I forgot to say, I didn't see any disrespect.  I see passionate people putting their minds and experiences together to help others learn their machines.  Sometimes you learn more on these forums than you can get out of local mechanics. (No disrespect if you are a mechanic!)

[MooneyMitch]

Roger that!

[moodychief]

I just finished a trip from Little Rock area to Moultrie Georgia to Savannah Georgia to Moultrie Georgia to Destin Florida back to the Little Rock area accumulating almost 11 hours of flight time and the generator is running fine. 

This puts Jezebel at 15 hours of flight time (and about 1 hour ground run-ups) since we flashed her generator.

[MooneyMitch]

That's the best news!  Congratulations.

[Jerry 5TJ]

I just finished the "eternal annual inspection" and test flew the 65C today.  Hurrah!

The Saga of the Generator:  

The generator seemed a bit loose so I put that on the squawk list for the annual last fall.  Turned out one of the bracket bolts was loose, so I took out the generator to get at the bolt.  With the generator out, I could see both brackets' holes were egg-shaped, so I took the brackets out and had them welded up so I could drill nice round holes again.  When I took the brackets out I could see the bolts were from the auto parts bin and not from Lycoming, so I bought new bolts with the proper drilled-for-safety-wire heads. 

While the generator was out I wanted to change the brushes.  The brushes were REALLY worn, and the brush arms were loose, and the brush springs seemed flabby...so I sent the generator out for remanufacturing.  It came back with new everything including bearings, brushes, brush arms, springs, contacts, newly epoxied and rewound coils and proper FAA paperwork...the rebuilder commented "it looked really old inside."   Gee, nothing in any of the logs about the generator since 1965 so maybe it was "vintage" Mooneybird factory stock?

Once all hung back in the plane and aligned properly, it came on line just fine.  At 1200 rpm (Zeftronics controller) it charges to about 12.6V, and at 1500 rpm it reaches the 14.2 volt regulator control limit. 

So, a $300 generator rebuild and about 16 hours of my labor and it is all better.   I think the moral of this story is -- a good generator and a solid-state controller are darn near as good as the alternator (but heavier). 

 

[jpusser]

Jerry I sent you a PM

[231Pilot]

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[GeorgePerry]

Quote: petterrjx

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[Parker_Woodruff]

Do you really think posting unintelligible stuff like this somehow will profit you?  Are people this dumb?

[Mooneymite]

Quote: Parker_Woodruff

Do you really think posting unintelligible stuff like this somehow will profit you?  Are people this dumb?

[craigsteffen]

On 2/5/2011 at 6:03 PM, Jerry 5TJ said:

Once all hung back in the plane and aligned properly, it came on line just fine.  At 1200 rpm (Zeftronics controller) it charges to about 12.6V, and at 1500 rpm it reaches the 14.2 volt regulator control limit. 

So, a $300 generator rebuild and about 16 hours of my labor and it is all better.   I think the moral of this story is -- a good generator and a solid-state controller are darn near as good as the alternator (but heavier). 

Nice that the rebuilt generator fired right up.  That means that they polarized it after they assembled it.  (I guess they would have had to to test it, so no huge surprise.)

Having just upgraded from generator to alternator, I'll add my two cents.  I agree that a generator plus good modern regulator is mostly equivalent to an alternator, BUT ONLY IF your taxi times are brief and if you DON'T do much takeoff/landing practice with taxi-backs.  I just got tired of deeply discharging my battery and then having the big charging surge upon taking off.  Due to a combination of the generator, and a getting-old battery, and some suboptimial wiring arrangements, I think my avionics bus voltage was getting lower than ideal, causing some flakiness in my Garmin 430.  I replaced the battery last winter, and then now with the alternator swapped in and the wiring arrangements improved, it's rock solid.  The bus voltage basically never drops below 14V, and the battery is charging immediately after engine start, and there isn't any surge of charging when I go to takeoff power because the battery is already completely charged by that point. 

The polarizing discussion is interesting.  I know you can polarize a generator with engine off; I've done it with my vintage VW.  You do get battery voltage to the generator though; I guess you could do that by bridging the right wires at the regulator with the master on.  But thinking about it, there's another connection you have to make; you have the ground the field wires.  So you can probably do it in the airplane, but you have to have *two* wires to do it.  Possibly to polarize in the plane, you have to ground the field terminal and connect the battery line to the generator output line (BRIEFLY).  Obviously to test this you'd have to have a generator that had lost its polarization, in an airpane, and then test this technique.  Perhaps I'll try this with the generator that's been removed.  I'll have to figure out a way to destroy the polarization to test this for sure. 

[Jerry 5TJ]

Thanks for reminding me of fun old times.   The C has moved to new stewardship but still has the generator, I believe.   

My present ride has a generator, too, one rated 28V at 150 amps.   As a backup there’s a 70 amp belt-driven alternator.  

Since this engine idles at 52% rpm getting the generator “on line” during taxi is less of a problem than with an O-360 ticking away at 850 rpm. 

[carusoam]

Great response, Jerry!

-a-

[Yetti]

One day I saw the Grumpy IA out flashing a generator.   Increased my trust level in him that he knows what he is doing.   https://m.aircraftspruce.com/catalog/pdf/zeftronicsinstall.pdf

[moodychief]

Does that have the same 50Amp Generator as the C mode?  If so, I am interested.