Alternator issues pa-28-181

cowman

cowman

Final Approach
Joined
Aug 12, 2012
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Display name:
Cowman
Aircraft is a 78 Piper Archer II

Cliff Notes Version:
Had an alternator failure on my long cross country earlier this year. Turning field switch off then on again would temporarily fix it but it would come back in shorter intervals. Had the voltage regulator replaced and it seemed to have fixed it. Flown another 15-ish flight hours and now annunciator light came on and no charge on ammeter. Turning field off/on no longer fixed it but after landing the light went off and it showed charging. Mechanic replaced brushes in alternator but on test flight the light came on again just after rotation with no charge. Landed and after landing light is off and alternator is charging again. Going to talk to mechanic again tomorrow.


Full Narrative:
Earlier this year on my trip out to CA I had an alternator failure in flight... I didn't notice the annunciatior light(I assume) because I was busy negotiating LAX area traffic, it was bright and sunny out, and the light is pretty dim when there's an actual problem. First sign was when my panel shutdown mid-transmission with ATC. I tried turning the master switch off then on again which resulted in everything coming back up... ammeter shot somewhere over 35(35 is the middle and about where it sits for a minute after startup before dropping). Everything worked fine after that point, I got back in touch with ATC and completed the flight ~45min. As one would expect the ammeter slowly came down to it's normal position about 1/4 of the way up between the 0 and 35 marks. On the ground I tried turning on everything electrical, running the airplane up, etc and could not reproduce the problem.

As there was no mx available where I was, it was a VFR day, and I couldn't reproduce the issue I chose to move on to my next stop. Shortly after leveling off the annunciator light came on and the ammeter dropped to 0. I turned the alternator field switch only off then back on and once more the annunciator turned off and the ammeter showed a charge. A few minutes later again the light comes on and no charge so I reset it.... repeated this several more times with the interval getting shorter each time until it wouldn't reset. I landed short of my destination in Yuma, AZ. After a weekend of messing around culminating in an alternator shop bench testing the alternator and verifying it showed it was outputting full power I limped on into to Chandler, AZ where a shop was able to replace my voltage regulator. After the voltage regulator was replaced the issue seemed to have been solved... I flew all the way home with no issues and made a couple more flights after that again with no issues.

Now, I should mention here that I'd consulted with some Piper owner's groups and they'd suspected an overvoltage protection relay to be the problem and that certainly seemed to match the symptoms... as the battery got all the way charged up the alternator would stop working. On the way to chandler I tested that theory by turning the field off for 5+ minutes before turning it back on and indeed it would stay charging longer if I did that. I couldn't find this overvoltage relay though and was informed by the shop at Chandler that by my model year of Cherokee it had been integrated into a single unit with the voltage regulator- so if this is all correct both things were replaced and as I said it seemed to have been fixed.... at least for the next 10-20 hours of flight time.

So flight before last on the way home my alt light comes on again and ammeter at 0. Here we go again. This time turning the field off/on again doesn't seem to help. I made it home and noticed around the time I landed my alternator was charging again, seeming to be at full output. I talked to my mechanic and he was pretty sure the brushes in the alternator must be worn out so he replaced them.

Just got a chance to do a test flight today- a week later. Airplane started up, taxied out, did a runup, no trouble. Then just after rotation the god forsaken alt light is on again and ammeter at 0. Alt field reset does nothing. Stayed in the pattern, landed, noted after landing the light is off and ammeter shows charging again. Mechanic had gone home for the day so I left a note. Looking for suggestions.
 
I don't recall the exact manufacturer but the new one they put in looked identical to the old one, there was no sticker on the housing but otherwise it looks just like this one.
IMG_4540.jpg
 
The VR and over voltage systems can be checked on the bench. Procedures are in the service manual.
 
Well, after checking all the connections they tried and tried and finally got it to fail on the ground. I'm told it only did it once under high RPM and only the one time but at least someone else saw it and I'm not insane. They say there was still voltage to the field when it quit so the current theory is something wrong in the windings. Remanufactured alternator is on the way.... hope this solves it for good.
 
cowman said:
Well, after checking all the connections they tried and tried and finally got it to fail on the ground. I'm told it only did it once under high RPM and only the one time but at least someone else saw it and I'm not insane. They say there was still voltage to the field when it quit so the current theory is something wrong in the windings. Remanufactured alternator is on the way.... hope this solves it for good.
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Congrats. That’s a nasty one to troubleshoot until the winding wire with the break in it go open and stay open.
 
cowman said:
Remanufactured alternator is on the way.... hope this solves it for good.
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I had exactly the same set of symptoms in the club's PA-28-181 Archer II. Swapping in a new alternator was the cure! -Skip
 
An awful lot of alternators get replaced because their $20 pair of brushes are worn out. A capable mechanic, doing the recommended 500-hour alternator inspection, can remove the alternator, clean and inspect it, replace the brushes if they're getting short, and put everything back together, in about an hour and a half. But, nope. Most of them get flown until the lights go out. If the brushes get really short they come right out and the springs behind them trash the slip rings.

Brush wear, or brush contamination by too much rear bearing grease, is by far the single biggest cause of alternator failure. Broken windings or failed diodes are rare in comparison.
 
cowman said:
Remanufactured alternator is on the way.... hope this solves it for good.
Click to expand...

Moot point now, but the best thing you could have done was get a PlanePower instead of a reman. If it's not on yet, send it back immediately.
 
Unit74 said:
Moot point now, but the best thing you could have done was get a PlanePower instead of a reman. If it's not on yet, send it back immediately.
Click to expand...

The Plane Power alternator has absolutely no magic in it. It uses all the same technology that the OEM alternators use. Brushes and everything, and if it doesn't get inspected at regular intervals it will eventually fail, too.

The biggest problem with remans is that the tech often puts too much grease in that rear bearing. It squeezes out when he assembles the alternator, and it gets on the slip rings and contaminates the brushes, creating a high-resistance sludge that severely limits field current and therefore the alternator's output capacity. I've lost count of how many times I've seen that. It's disgusting that this error persists as long as it has. First saw it around 15 years ago.

Heavy trucks have been using brushless alternators for over 30 years. I wish I knew why auto and aircraft makers can't come up with a small brushless alternator that will fit the application. THAT would be a true improvement.
 
Dan Thomas said:
An awful lot of alternators get replaced because their $20 pair of brushes are worn out. A capable mechanic, doing the recommended 500-hour alternator inspection, can remove the alternator, clean and inspect it, replace the brushes if they're getting short, and put everything back together, in about an hour and a half. But, nope. Most of them get flown until the lights go out. If the brushes get really short they come right out and the springs behind them trash the slip rings.

Brush wear, or brush contamination by too much rear bearing grease, is by far the single biggest cause of alternator failure. Broken windings or failed diodes are rare in comparison.
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And alternator brushes are about the lowest cost replacement part you'll ever find on your airplane.
 
Dan Thomas said:
I wish I knew why auto and aircraft makers can't come up with a small brushless alternator that will fit the application
Click to expand...
On the aircraft side, mainly weight and drive torque requirements. But they are much larger in size since they're basically 2 alternators bolted together. They do use brushless on large aircraft turbofans and several large helicopters but they are driven via the engine gearbox or main transmission where there is "plenty" of room to mount them.
 
Bell206 said:
On the aircraft side, mainly weight and drive torque requirements. But they are much larger in size since they're basically 2 alternators bolted together. They do use brushless on large aircraft turbofans and several large helicopters but they are driven via the engine gearbox or main transmission where there is "plenty" of room to mount them.
Click to expand...

But if Plane Power (who, I am sure, is simply adapting an existing automotive unit) can make an alternator that produces 70 amps in a smaller and lighter package than the 60-amp Ford alternator, I'm sure someone can make a brushless that would be no bigger than the Ford. That field only needs about 4 amps, max, and a tiny stationary winding and matching rotor pickup winding and diodes wouldn't take much more room than the existing slip rings and brushes. There's a bunch of empty space in the back of the alternator now, between the diode plates and rotor.

I wonder if the G forces on the diodes is a limiting factor. Small alternators spin a lot faster than large ones.
 
Dan Thomas said:
I wonder if the G forces on the diodes is a limiting factor.
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I don't think the reason has to do with the internal limitations so much as the physical limitations: drive torque and weight. To make the brushless type fit/supported in the same location on a small aircraft or car as a slip ring/brush type would require extensive modification or design change (read cost) that the market wouldn't support the more expensive alternative. If conventional alts failed on a more regular schedule like vacuum pumps it might give more traction to a brushless version.
 
Dan Thomas said:
The Plane Power alternator has absolutely no magic in it. It uses all the same technology that the OEM alternators use. Brushes and everything, and if it doesn't get inspected at regular intervals it will eventually fail, too.

The biggest problem with remans is that the tech often puts too much grease in that rear bearing. It squeezes out when he assembles the alternator, and it gets on the slip rings and contaminates the brushes, creating a high-resistance sludge that severely limits field current and therefore the alternator's output capacity. I've lost count of how many times I've seen that. It's disgusting that this error persists as long as it has. First saw it around 15 years ago.

Heavy trucks have been using brushless alternators for over 30 years. I wish I knew why auto and aircraft makers can't come up with a small brushless alternator that will fit the application. THAT would be a true improvement.
Click to expand...


Weigh both of them and report back please. In fact, I just, like 2 months ago replaced mine with a Plane Power.
 
Unit74 said:
Weigh both of them and report back please. In fact, I just, like 2 months ago replaced mine with a Plane Power.
Click to expand...

Yes, I know they're lighter. I have installed them. My point was that they're not immune to brush wear, the most common cause of alternator failure.
 
Front-mounted alternators operate in an awful vibration environment in any four cylinder opposed engine (i.e. Lycoming 320s and 360s). The structural strength of the housing and the mounting to the engine case are frequently the life limiting factors.
 
.......and we’re still not fixed. Reman put on, took a test flight. While doing a steep turn the smell of ozone filled the cabin and the field breaker popped.


Yippie.
 
So the word is the voltage regulator I got back in AZ has cooked it’s self and that’s where the burnt wire/ozone smell is coming from. So now we get to try to get ahold of someone to warranty it. Super. Fantastic.
 
A week now trying to get someone on the phone or calling the right people or whatever it takes to get the thing replaced. Zeftronics has now twice promised to contact my mechanic and not done so. Finally got a different person on the phone this morning who seemed more helpful. I gave him the whole narrative and he agreed it sounded like the voltage regulator was defective, said the person who does the RMA numbers was out to lunch and as soon as she got back he'd call. That was about 3 hours ago.... and now I call and just get sent to a voicemail.

In the meantime I still can't fly and I don't even know if or when I'll have a part on the way. I tried to tell the guy I was willing to buy a new one and let them refund me when they got the defective part. At this point I'm pretty much willing to just give up on the warranty and buy a new one.... preferably not from Zeftronics if this is their typical customer support.
 
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