Alternator

[75_M20F]

Any advice on when to change out the alternator?

Mine is working fine, but it appears to have been on the airplane for a couple decades without service.

Mechanic said brushes have over 50% left and the bearings are still good at last annual.

I just have a "fear" of it failing and leaving me stranded somewhere, so I was considering changing it out.

Thoughts?

 

 

[1964-M20E]

I've never heard of changing an alternator as you describe.  Not that you can't do it but there are things called infant mortality and maintenance induce failure to consider as well in you decision.  I know people will change things like this during a major overhaul.

I know whenever something is changed on my plane, vehicle or anything else I worry more about that part or item initially than I was worried before it broke or was changed.

My opinion is if it's not broke don't fix it.

[MBDiagMan]

Your mechanic gave you your answer: bearings good, brushes, good.  As long as it is still charging correctly as well, there is absolutely no need to change it.  If it is not broke, don't fix it.  On an airplane I would not always say this, but in this case, I believe it is best left alone.

 

my $0.02,

[Oldguy]

Have to agree with everyone else - MIF (maintenance induced failure) and infant mortality are bigger concerns to me than the possibility of a properly running alternator failing.

BUT....if it is really weighing on your mind, go ahead and buy a spare alternator and carry it with you. The biggest problems I have heard entail not finding an alternator when one does fail and being AOG for several days. Most places you land will have some type of mechanic or know how to get one. But I would avoid changing it just to change it.

FWIW

[Yetti]

sleeping dogs

[mooniac15u]

Based on another MS thread I believe the OP is in the middle of a major overhaul.  Not sure if that changes anyone's opinion.

[Jim Peace]

2 hours ago, Mooney_Mike said:

Any advice on when to change out the alternator?

Mine is working fine, but it appears to have been on the airplane for a couple decades without service.

Mechanic said brushes have over 50% left and the bearings are still good at last annual.

I just have a "fear" of it failing and leaving me stranded somewhere, so I was considering changing it out.

Thoughts?

 

 

This all depends on your typical mission.  If you always fly close to home you can take a chance.  If you cross the country a lot like I do then the last thing you want is to be AOG in a foreign land.  Dispatch reliability to me is worth more than saving a few bucks on an alternator that has been installed over two decades ago with no recent mx on it.

If you have a "fear" of it failing that may be the universe telling you that it may be time.  

Weigh the cost difference of doing it now at your home airport vs on the road with all the $$ and logistics involved.......

If it were me it would be replaced with new....or at least sent out for overhaul...........

Edited March 2, 2017 by Jim Peace

[carusoam]

Mike,

do you have the same fear of failure of...

- vacuum pump

- starter

- voltage regulator

- nose wheel

- oil cooler

- fan belt

- battery

There are reasons to change all of these out.  But none of them will make you feel better by changing them out.

If it makes you feel better, go ahead and change it...

if it isn't charging properly, look at what voltage regulator you have. Have it adjusted...?

You are probably not going to find much support for changing out something that isn't worn or broken before its time...

The generator on my 65C wouldn't die. But it got a new belt every decade or so and some brushes when they were worn. Finally, it got swapped out for an OH'd one. What it really needed was a digital voltage regulator....

When flying in IMC, balance the need for for having proven stuff that works with the desire to replace stuff that doesn't need it to be replaced.

what is the voltage it is charging at?  Do you have a panel mounted volt meter?

If you are only flying in VMC the critical nature isn't very big.

If you have fear of no electricity...

1) Consider getting a VR from Zeftronics that has little lights for your panel.  One that lights up when the alternator craps out...

2) Get a new battery with a tested capacity.

3) Bring a second battery along for running your portable nav and com equipment. It will come with a compressor....

Try to determine what the source of your fear is...  

how does that sound?

Best regards,

-a-

 

[75_M20F]

43 minutes ago, carusoam said:

Mike,

do you have the same fear of failure of...

- vacuum pump

- starter

- voltage regulator

- nose wheel

- oil cooler

- fan belt

- battery

There are reasons to change all of these out.  But none of them will make you feel better by changing them out.

If it makes you feel better, go ahead and change it...

if it isn't charging properly, look at what voltage regulator you have. Have it adjusted...?

You are probably not going to find much support for changing out something that isn't worn or broken before its time...

The generator on my 65C wouldn't die. But it got a new belt every decade or so and some brushes when they were worn. Finally, it got swapped out for an OH'd one. What it really needed was a digital voltage regulator....

When flying in IMC, balance the need for for having proven stuff that works with the desire to replace stuff that doesn't need it to be replaced.

what is the voltage it is charging at?  Do you have a panel mounted volt meter?

If you are only flying in VMC the critical nature isn't very big.

If you have fear of no electricity...

1) Consider getting a VR from Zeftronics that has little lights for your panel.  One that lights up when the alternator craps out...

2) Get a new battery with a tested capacity.

3) Bring a second battery along for running your portable nav and com equipment. It will come with a compressor....

Try to determine what the source of your fear is...  

how does that sound?

Best regards,

-a-

 

Well, the vacuum pump did die on me in November while VMC (thank goodness). Got a vacuum light and a flag so it was obvious.

My engine is off the airplane and out for overhaul, so that brought the alternator to my thought process.

I just looked through all the logs. Nothing anywhere concerning the alternator, so it may be OEM.

It was charging fine prior to the engine removal at least.

My mission on the plane is that I will soon use it to commute to work. I will also be flying it out to KRNO this fall. 

How long do these alternators last?

Anyway, thanks for the input.

I like the idea of buying one and just putting in the cargo area to avoid waiting a week for one to be shipped should I need one while out west.

 

 

 

 

 

Edited March 2, 2017 by Mooney_Mike

[carusoam]

Mike, the key thing is how you are going to use it.

When I use things for work, they get maintained to a much different level than the third car in the driveway...

I have no reason to wear tires to the cords on my wife's work vehicle.

everything firewall forward should be reviewed for what the cost of replacement is vs the cost of not being able to use the plane for a day...

if i couldn't use my plane for a month I wouldn't have much of a change.

There are a few of us here that use our planes as their daily transport.  They also have an extra vehicle at the other airport as well.

The focus may be on ultimate reliability, not on what other guys are doing...

dispatch reliability and single engine aircraft reliability and an instrument panel to navigate in low IMC.

it wouldn't make a lot of sense to hold onto something that can hold you back for a few hundred bucks...

What do you think of dual alternators, batteries and anti-ice systems...?

there are newer lighter starters and alternators that make sense.  The original equipment is automotive based and probably goes longer than the motor TBO.

Best regards,

-a-

Edited March 2, 2017 by carusoam

[75_M20F]

Well, if I need anti-ice then I will be driving that day. I don't fly my M20 in "challenging" conditions.

Dual alternators is an interesting idea. I saw where one can replace the vacuum pump with a small backup alternator, it bolts right in the same spot the vacuum pump used to occupy..

For now I will stick with the vacuum pump setup and 1 alternator.

I read on here alternators from Kelly are low quality? Can anyone vouch for that? What brand is best?

 

[ArtVandelay]

Didn't 201er have his alternator die on his way to Cuba just last year?

[Mooneymite]

Once, long ago, I took my Mooney alternator to an alternator shop to have it checked out.  The over-hauler took one look at it and said it was identical in every way to a Ford alternator except for the tag which made it illegal for him to do anything but check it out.  As I recall, at that time a rebuilt Ford alternator was about $40, a new alternator for my Mooney was about $800 + shipping and tax.  

Since then, my second airplane has always been an experimental.

[N201MKTurbo]

I've never had an alternator just quit. I've had the field wire break a few times that made it quit, but that is not an alternator failure. 

They usually fail a little at a time. Things like bad internal connections that reduce the output and make them noisy.

[1964-M20E]

17 minutes ago, Mooneymite said:

Once, long ago, I took my Mooney alternator to an alternator shop to have it checked out.  The over-hauler took one look at it and said it was identical in every way to a Ford alternator except for the tag which made it illegal for him to do anything but check it out.  As I recall, at that time a rebuilt Ford alternator was about $40, a new alternator for my Mooney was about $800 + shipping and tax.  

Since then, my second airplane has always been an experimental.

You should have bought the ford alternator from him and took all the guts and put it into the original Money alternator case.

I ran into similar thing with the generator form my 64 E model I found some brushes and changed them which worked for a while then I went to  Plane Power alternator.

 

 

 

[Mooneymite]

14 minutes ago, 1964-M20E said:

You should have bought the ford alternator from him and took all the guts and put it into the original Money alternator case.

Or tell him (wink, wink), it's off an air-boat.  

That sign off would make pretty entertaining log book reading.  

[DonMuncy]

7 hours ago, Mooneymite said:

Once, long ago, I took my Mooney alternator to an alternator shop to have it checked out.  The over-hauler took one look at it and said it was identical in every way to a Ford alternator except for the tag which made it illegal for him to do anything but check it out.  As I recall, at that time a rebuilt Ford alternator was about $40, a new alternator for my Mooney was about $800 + shipping and tax.  

Since then, my second airplane has always been an experimental.

Did you ask him to show you the tag; so you could point it out to a hangar elf; so he could remove it before taking it to the alternator shop for repair.

[kortopates]

When I had my engine off to address an engine mount issue, I replaced the brushes and bearings in my #1 alternator and cleaned it up inside. My #1 which is gear driven and really hard to get access too when installed on the engine. It was all my own labor anyway and the parts aren't expensive. It has given me many years of trouble free service before and i expect it will again for many more years. But I would never replace a good working alternator with O/H exchange. Its too easy to just replace the wear parts and clean them up. In addition to the unwarranted high expense that seems like unnecessary risk as well. My #2 which is belt driven, and is easily accessible in about 10 min so in that case since its my second one, it can wait till I see a problem. I can still dispatch with one. 

[Mooneymite]

34 minutes ago, DonMuncy said:

Did you ask him to show you the tag; so you could point it out to a hangar elf; so he could remove it before taking it to the alternator shop for repair.

Sad, but my old alternator may be PMA'd in an old, beat up Ford somewhere!  

[cliffy]

I've done mine in the past by doing bearings, brushes and slip ring reconditioning in a lathe (parts from the "official" manufacturer). It lasted until the O/H, 800 hrs later.  Got a new one at O/H 1,000 hrs ago still going strong. It's an old "Motorola". Now, not even being made anymore. Would be forced to change to something else if it fails. I'm VFR now a days so I'll go till it fails. 

[gsxrpilot]

On 3/2/2017 at 8:55 PM, kortopates said:

When I had my engine off to address an engine mount issue, I replaced the brushes and bearings in my #1 alternator and cleaned it up inside. My #1 which is gear driven and really hard to get access too when installed on the engine. It was all my own labor anyway and the parts aren't expensive. It has given me many years of trouble free service before and i expect it will again for many more years. But I would never replace a good working alternator with O/H exchange. Its too easy to just replace the wear parts and clean them up. In addition to the unwarranted high expense that seems like unnecessary risk as well. My #2 which is belt driven, and is easily accessible in about 10 min so in that case since its my second one, it can wait till I see a problem. I can still dispatch with one. 

So in cruise, are you running off #2? I'm thinking that since #1 is much more expensive just to get to, I should not use it any more than necessary. Is there any reason to use #1 unless #2 has quit on me?

[milotron]

I would think that putting electrical load on #1 would not wear it any faster. The wear items are bearings and brushes, both of which will be spinning and wearing under load or not. The brushes may last slightly longer due to arcing/heat load but not significantly I would think.

 

In my opinion, better off having them both on line, sharing the load somewhat, and providing true redundancy without any action required from the operator in case one does fail.

Since reading others comments on the forum, i HAVE started religiously turning on #2 ( the belt driven ) alternator first so the initial charging surge is absorbed by that unit and not the somewhat fragile gear/spline drive on the #1. This is more about the coupling than wear on the alternator itself. Once up to speed the loads should be fairly stable and not shock load the coupling too much.

[kortopates]

1 hour ago, gsxrpilot said:

So in cruise, are you running off #2? I'm thinking that since #1 is much more expensive just to get to, I should not use it any more than necessary. Is there any reason to use #1 unless #2 has quit on me?

They are always both on and I fail #2 during the runup to verify #1 takes the full load, but with both on line #2 is taking 2/3's if not more of the load. As such, over the years my #1 has done very well. Bearings are getting the same wear, but the lesser load has appeared to allow the brushes to wear at a bit lower rate compared to the servicing I have done to my #2. Buts that's a unscientific observation (I didn't do any measuring). 

[Bartman]

Had mine rebuilt two years ago due to popping of the breaker under high power climb.  He replaced the brushes, cleaned it up, and I think the field wire needed some attention which was probably the real problem.  No issues since then. 

If it is 20 years old and it caused me grief I'd rebuild it before letting it fail and end up with one of the Kelly rebuilds. I used to see lots of posts about poor quality rebuilt exchanges, but Not in a couple of years.