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Alternator Fooled Me

DanH

Legacy Member
Mentor
There I was, flying along, minding my own business, and I get an "EIS VOLTS" warning. Uh oh, losing an alternator.

Pulled the cowl when I got home. Internally regulated Plane Power, so basic diagnosis is simple. If you have bus voltage at the B lead, and bus voltage at the red wire, the problem is internal to the alternator. I had good volts, so off it came.

Quick inspection inside the back cover didn't turn up anything obvious. Pulled the regulator/brush assembly. Brushes look good, commutator is smooth, about 3 ohms through the rotor (field) windings, no short to ground. Hmmm. pull the rectifier screws, stand up the stator connections, and they check good too. Ok, doesn't leave much, so I get a new IC regulator from a buddy and installed it. Back on the airplane it goes....and doesn't charge. Whatttt?

Recheck field power, and the B lead, and make sure it's not an indication problem by cycling the EFIS from main buss to backup battery. All good. Out of time, got a business trip in the AM, so I buy a new, identical 60 amp Plane Power (Hartzell Engine Technologies is right here in Montgomery). I'll get the old one shop-checked and overhauled as necessary, then I'll have a spare.

Out to the airport, bolt on the new alternator, do a run-up....and it doesn't charge either.

Finally I go into Old Car Guy mode. Forehead slap; I've seen this before, and besides, there isn't much left. I walk around to the front, pull out the three prong field/indicator plug, and look real close with a 10X magnifier. Nope, hadn't missed a burned socket, and they all looked clean, but just the same, I squeezed the sockets closed just a bit, and plugged it back in.

Yep, that was it; a runup said I was now blessed with many vigorous electrons.

Problem appears to be unsupported wire where it exits the back of the plug. The little square sockets in the plug are not held tightly by the plug body, so the socket and wire can vibrate around. Eventually wear/debris/corrosion/loss or spring pressure makes the connection(s) intermittent or non-conductive.
 
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Heat and Cold

Those srping contacts are tempered and I've seen them do this, figuring it is from hot and cold cycles. Sometimes they just aren't seated right from the beginning, and the constant vibration causes fretting and dust which only gets worse over time.

I had a customer last month who had replaced an alternator due to intermittent low voltage warnings. I like to troubleshoot 12V wires with an incandescent bulb, as it will show flickering or dimness when connected along the path of the wire. In this case I could make the light flicker by pulling on the main cable. I peeled back the tape wrapped around the crimp at the alternator and sure enough it was a really bad crimp. Placing a new, properly-crimped terminal on the wire did the trick.

They, too, have a spare alternator.

Vic
 
the question is, why did it fail?

Indeed! Disturbing that this isn't the first plug failure. Is it vibration? It must be, as the current certainly is not above normal. But what to do? Will Hartzell now dig into the true root cause and give us a solution?

edit: Aren't the Hartzell guys hometown boys now? Drop by the office!
 
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If I had to guess, I'd venture that Plane Power isn't buying these plugs from Denso, but rather in the auto parts aftermarket.

Maybe, but I just got mine out of the bag and it has tefzel wire, so I don't think the automotive would have that wire. Maybe inferior specification for the terminals?

From the effort they took for the wire, I would assume they would want to cure a termination issue. Seriously, aren't the PP guys now working out of Montgomery?

Edit: Maybe that is the issue - the tefzel wires are stiffer than automotive. Maybe everything else is ok, but the vibration is not acceptable with the stiffer wires. Thoughts?

If so - then potting the entrance might reduce internal motion. I had decided not to do this so the terminals could be removed, but I am rethinking.
 
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Could this have been Rosie's problem? He's in St. Kitts now and planning to fly back into Florida tomorrow. Maybe he'll read this and reply.

This was the cause of the second failure, and I should have 'squeezed' the fast-on connectors! Rosie

PS: We hope to make it from St. Kitts to Great Exuma on Friday, Florida and beyond on Saturday...


P.P.S. Friday afternoon update, prior to this writing at 3:40 pm CDT, from Rosie's Spot Tracker, it appears he has successfully landed at Great Exuma!
 
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I've experienced a couple of instances where I only had alternator output at higher rpm. The first instance was cured by re-seating the round plug (Denso).

The symptom reappeared many months later. A close look at the plug revealed the locking tang on the female spade lug didn't always hold depending on how the wire wiggled.

Bent the tang for more "grab" and better secured the wire bundle.

So far so good.

Don
 
Plane-Power Connector

If I had to guess, I'd venture that Plane Power isn't buying these plugs from Denso, but rather in the auto parts aftermarket.

When I broke the crimp portion off of one of the contacts for my alternator, I decided to search for a source of connector parts for spares. You know, I could not find a similar size and form-factor Denso alternator with that connector, but I did figure out that the connector is made by Sumitomo and I was able to find parts online somewhere...

One thing that I did find and purchase were rubber wire seals that are designed insert into the wire end of the connector. I chose to install these, because I feel that this provides support to the wire and adds some strain relief to the contacts themselves from wire vibrations. I suppose this might also help keep the contact itself from spreading open if this phenomenon is caused by vibration of the wire near the contact.

Skylor
 
From the effort they took for the wire, I would assume they would want to cure a termination issue. Seriously, aren't the PP guys now working out of Montgomery?

Yes, the Plane Power business unit is now at the Selma Hwy facility. I've already spoken to a friend in tech there.

Edit: Maybe that is the issue - the tefzel wires are stiffer than automotive. Maybe everything else is ok, but the vibration is not acceptable with the stiffer wires. Thoughts? If so - then potting the entrance might reduce internal motion. I had decided not to do this so the terminals could be removed, but I am rethinking.

I like the thought well enough to silicone the back of the plug next time the cowl is off.
 
As a minimum PP should use these . .

wire inlet seal from Sumitomo.
Screen%2520Shot%25202015-05-01%2520at%25207.14.29%2520AM.png


And possibly the gold plated terminals instead of the tin.

I have contacted a terminal supplier in Mich to see if they can get these. For all of us with product already, the potting with RTV should do the same. The only question is - if the connector body will move too. Hours shall tell.
 
Had similar issue

I have a 35 amp Denso I bought through VANS on my -4. I had both connectors inside the plug crack in half (female side)at different times, but near the 150 hr. mark.First time I had the ALT warning light and no volts because it was the feed side. The second time, I had no idiot light with engine shut down because the indicator wire failed. My wires are all well run and secure, along with a boot over them. I attribute the failures to vibration and have since filled the plug backs with silicone to see if that helps.
 
wire inlet seal from Sumitomo.
Screen%2520Shot%25202015-05-01%2520at%25207.14.29%2520AM.png


And possibly the gold plated terminals instead of the tin.

I have contacted a terminal supplier in Mich to see if they can get these. For all of us with product already, the potting with RTV should do the same. The only question is - if the connector body will move too. Hours shall tell.

Gold terminals are not the solution. Gold migrates under high current flows, so it usually restricted to non-power applications. As for RTV potting, use 'sensor safe' product, but not generic silicone that uses acetic acid (vinegar smell).

In my too long and not so illustrious career, I would estimate that 75% of the failures that I have seen with herding electrons are related to connections. I call it the 'social media' debugging model... Check your connections first!
 
Butt splice connectors

This is a timely topic for me. I am just about to wire in my PP alternator. Since reliability is the most important factor for me, would it make sense to simply cut off the stock connector and replace it with butt splices? I could engineer in a service loop of wire on the firewall, away from all of the whirling parts near the alternator. What do y'all think?
 
Steve - I think you mean spade lug. I did this for a temporary test rig I built up. Worked fine for the short duration I used it.
 
Dang, I hope PP knows about this. I had an PP alternator issue some time ago that was never fully resolved. It acted like a loose connection. on-off-on-off at random times. It was never suggested to me to look at the connector. Of course I got a replacement, and the brand new one did the same thing!
 
No, I'm really thinking butt splice

Jon,
I am really thinking of a butt splice so there would be nothing to vibrate loose. If I ever have to replace the alternator, I would just cut out the splice and use another one, losing less than inch of wire (hence the service loop). Just a thought.
 
Gold terminals are not the solution. Gold migrates under high current flows, so it usually restricted to non-power applications. As for RTV potting, use 'sensor safe' product, but not generic silicone that uses acetic acid (vinegar smell).

Gold: Yeah, I was not sure about that, I was thinking wear from motion and oxidation. Thanks for the clarification. I am getting a quote and will change to the tin coated terminals.

Potting RTV formulation: Good to point out Vern. I neglected to mention.


Jon,
I am really thinking of a butt splice so there would be nothing to vibrate loose. If I ever have to replace the alternator, I would just cut out the splice and use another one, losing less than inch of wire (hence the service loop). Just a thought.

The PP that I have uses 2.3 mm male spade terminals in the alternator, Steve. Are you talking about eliminating the connector housing and just using the direct to terminal connections? If so then all the wire forces will be transmitted to the spade terminal and it may not be up to it. Best to just just consider potting the connector. I have no facts to say this is a valid fix to eliminate the root cause failure, but it should help.
 
If I was going to eliminate the plug at the regulator, I'd probably clip a heat sink to each pin in turn and solder a wire, then sleeve it with heat shrink, then pot the entire plug cavity. That would allow relocating a plug or splice someplace with limited vibration.

It appears to be what E-Mag does to the socket and pins on the Ford EDIS coil used on a p-mag.
 
Just as another point to consider, if you have a cross over exhaust, that connector is a only a couple inches in front of it on the PP unit. I used a heat shield to help mitigate the heat radiation. Also, I tested the potted regulator with a heat gun to the point of melting the potting. The regulator still functioned fine.
 
Plane Power Alt.

Dan, I probably should've posted this a couple of years ago when it happened. I had a similar failure with my Plane Power alternator. Same thing, flying over mountains in Colorado on my way to Gunnison. I was about 100 miles out when I get a "low Volts" indication. I cycled both the alternator switch and the ALT circuit breaker, no change. So I shut everything off, (dual mags), and continued to KGUC. After un-cowling and checking about everything I could think of, i charged the battery and flew home. (No charging on the way home either.)
Back at the hangar, I traced the field wire from the Split switch (Cessna type), to the terminals in the plug on the back of the alternator. "0" volts. I thought I had found the problem. (Switch). When the new switch came, I installed it and it worked. Problem solved?for about 5 minutes of flying. It quit again :(
Back to the hangar. This time I removed the alternator and sent it to Plane Power to have it checked out.
It came back with a clean bill of health. After installing and starting the engine, it still didn't work.
PHP:
Previously, I had checked the field (red wire) on the plug, and it had battery voltage. I decided to look again. I must be missing something where the wire enters the back of the plug. Then I found it! Where the red wire enters the back of the plug - a small part of the terminal end was protruding out from the back side. I pulled on the wire, and the terminal connector was broken! That was it! 
I called and ordered a new plug, with enough wire on it to go all the way back to the split switch. It now charges normally! Whew!
 
Connection

For the last month I have had the same problem only it was intermittent with the alternator coming and going. Saw this post on Friday, tweaked the connector on Saturday and the problem is solved. Thanks, I never did get to the point of pulling the alternator so once more the Van's Air Force did the leg work for me. Now if I could just find someone to polish the plane.
 
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Follow up: Tweaking the connector didn't work long term. Actually, it didn't work very long at all...maybe 10 hours.

Cut the plug off the harness and dissected it. Here's what the connectors look like when out of plastic housing. You're looking at top and bottom:



I un-bent the terminals to spread them open:



When spread open, here's the "spring" which is expected to maintain contact pressure:



The two contact surfaces of the field connection (face of the spring and the underside of the housing), lighted two different ways for contrast. There is no sign of overheating, just what appears to be fretting:





Sense terminal for contrast, which carries a lot less amperage:



Continued.
 
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The plastic plug itself, with its rubber gasket, appears to be firm in the regulator socket...no relative movement, no way for vibration to cause a problem. The issue appears to be that the above female terminals are simply snapped into the plastic plug, without any additional fixation. I think they are fretting and oxidizing the contact surface. I'm also going to look at "pinch" tonight, the degree to which the spring puts pressure on the contact area. I'm suspicious about the relative dimensions; thickness of the regulator pins vs the socket.

Even if the the contacts were not fretting, the wires need additional support in the plug. The white wire below is the warning light terminal; note that it has almost fatigued to total failure:



The surprising thing is how it fatigued with the wires secured as they were. All the terminal wires were zip-tied together about an inch from the back of the plug, then zip-tied to the B-lead a few inches further away, then the whole bundle was shrink-wrapped and held with an Adel clamp at the engine case split line.

The above terminals are now with a buddy at Plane Power, who will take it up with the engineers.

A new replacement plug did not incorporate any fixation, so I've potted it with a solvent based rubber compound.



Anyone believe dielectric grease in the sockets would be a good addition?
 
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Dan,

Dielectric grease is worthwhile especially since there is a risk of moisture with contacts that do not appear to be gold plated. Good idea - in fact I will call into my local auto parts store today to pick up a tube.
 
I had a similar problem. Checked, then replaced wires to the alternator. Intermittent problem would not go away. Met Bill from B&C at Oshkosh. He told me to replace the alternator plug. I told him I checked that and the wires were fine. He said REPLACE THE PLUG. He actually gave me a new plug. We replaced the plug and no further problems.
 
I had a similar problem. Checked, then replaced wires to the alternator. Intermittent problem would not go away. Met Bill from B&C at Oshkosh. He told me to replace the alternator plug. I told him I checked that and the wires were fine. He said REPLACE THE PLUG. He actually gave me a new plug. We replaced the plug and no further problems.

Was it the same plug, just new? Did it have silicone plugs surrounding the wires where they enter the plug?
 
Plan Power Plug

These could be available at the local auto parts store. I got a couple on-line at www.repairconnector.com Part no. RC1650, $12.99ea.. It comes with a 6" pigtail and three butt connectors. However, the wire is PVC, not Tefzel. Could come in handy in a pinch. I potted mine with grey, sensor-safe RTV.
You can find them other places also. Google "hitachi Nippon denso oval plug".
pp-plug_bag.jpg

pp-plug1.jpg

pp-plug2.jpg
 
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I just called PP to get a replacement plug and was told to order part number 11-1010 from aircraft spruce.. I went there only to find this plug and 3 wires to $105.00. what?...can that really be.?
 
I just called PP to get a replacement plug and was told to order part number 11-1010 from aircraft spruce.. I went there only to find this plug and 3 wires to $105.00. what?...can that really be.?

At which point I would simply giggle and mutter "Wanna bet?" and head to the workshop.
 
This is also a timely thread for me.
I have a PP 60 amp alternator with the idiot light. My ammeter only shows bus amps, not total amps. My PC680 battery is only about 6 months old.
Recently I notice the idiot light showing dimly at about 1200rpm and 14 amps.
At 28 amps the light is full red but the voltage shows 13v.
At 28amps and 2100-2400 rpm the light is on dimly even though the voltage is showing 13.9-14.1
First thought was loose belt, and it was a little loose but I adjusted it to the high end of the range and no change.

It doesn't make sense to me that I show plenty of voltage to be charging the battery and yet have a red light on. How is that idiot light wired exactly?
 
Amps went to ZERO!

Well, First off...Thanks Dan for this post! I didn't think I would have to use it, but on my way to Bowling Greens this week on the way up from FL my ammeter went to ZERO :eek:

It would have been nice if the builder set his VP100 alarm to 13 volts instead of 12! I was sitting fat dumb and happy drinking from my juice box and then my scan looked at the volts going down to 12.4v and surprised me!

I cycled my alternator switch on my VP100 OFF and then back ON with a successful reset. Battery back in charging state and all was good again.

Stopped for fuel in Albany, GA....took off and then an hour from KBWG it goes back to ZERO :eek:

Another successful reset and no other issues.

Once in KBWG I pulled off the cowling, plled the pulled off and then gently squeezed the 3 sockets to be a little tighter. It seemed to feel better when I plugged it back in.

Engine run confirmed good connection. Departed back home 4.5 hours with no issues all flight!

Seems like I will be changing out the plug with a new one to be sure.
 
Well, First off...Thanks Dan for this post! I didn't think I would have to use it, but on my way to Bowling Greens this week on the way up from FL my ammeter went to ZERO :eek:

It would have been nice if the builder set his VP100 alarm to 13 volts instead of 12! I was sitting fat dumb and happy drinking from my juice box and then my scan looked at the volts going down to 12.4v and surprised me!

I cycled my alternator switch on my VP100 OFF and then back ON with a successful reset. Battery back in charging state and all was good again.

Stopped for fuel in Albany, GA....took off and then an hour from KBWG it goes back to ZERO :eek:

Another successful reset and no other issues.

Once in KBWG I pulled off the cowling, plled the pulled off and then gently squeezed the 3 sockets to be a little tighter. It seemed to feel better when I plugged it back in.

Engine run confirmed good connection. Departed back home 4.5 hours with no issues all flight!

Seems like I will be changing out the plug with a new one to be sure.

Good you got back ok.

http://www.driftmotion.com/category-s/1847.htm

Has (separately) the 090 sumitomo terminals, connector housing and small plugs for stain relief in the back holes. This way you can reuse your tefzel wire to the plug. They ship pretty quickly. Genuine Sumitomo too. Yes, for the ND/PP alternator.
 
Solution?

This is also a timely thread for me.
I have a PP 60 amp alternator with the idiot light. My ammeter only shows bus amps, not total amps. My PC680 battery is only about 6 months old.
Recently I notice the idiot light showing dimly at about 1200rpm and 14 amps.
At 28 amps the light is full red but the voltage shows 13v.
At 28amps and 2100-2400 rpm the light is on dimly even though the voltage is showing 13.9-14.1
First thought was loose belt, and it was a little loose but I adjusted it to the high end of the range and no change.

It doesn't make sense to me that I show plenty of voltage to be charging the battery and yet have a red light on. How is that idiot light wired exactly?


Ever find the issue?
 
At PP's suggestion I replaced the voltage regulator unit which includes the brushes. This made no difference to the behaviour of the red light, but there was a change in the way the regulator behaved. It seems more 'dead beat' than the old one. It ramps up the voltage much more slowly and also puts out a lower voltage at low rpm.
I plan to remove the alternator and get it tested. Our local shop was too backed up at the time but I'll give it a go when I have the cowling off next.
I can't fault its performance, but that light should not be flickering.

Did you have a similar problem?
Jim
 
At PP's suggestion I replaced the voltage regulator unit which includes the brushes. This made no difference to the behaviour of the red light, but there was a change in the way the regulator behaved. It seems more 'dead beat' than the old one. It ramps up the voltage much more slowly and also puts out a lower voltage at low rpm.
I plan to remove the alternator and get it tested. Our local shop was too backed up at the time but I'll give it a go when I have the cowling off next.
I can't fault its performance, but that light should not be flickering.

Did you have a similar problem?
Jim

Yeah the other night flying home for Christmas .. it flickered and then stayed on steady with 14.6 volts and 2 amps.. I found a broken ring terminal on the main airplane ground cable engine to airframe and thought that was it .. I replaced that terminal and still have an alternator light on .. tested many things today and still have the light .. I turned every electrical switch on and it still maintains 14.4 volts and 2-3 amps. I'm stumped.
 
Recently, my low voltage light light began to appear frequently, on and off, for the better part of an hour. When I went to the EFIS engine page, the voltage was fluctuating up and down from 12.6V to 12.1. ( the alarm limit 12.0). No matter how long I watched, the voltage never stayed steady, it was constantly up and down across 0.5V spread, almost sinusoidal in pattern. I could see the alarm sound whenever the voltage dropped below 12. Turning on the boost pump dropped the bottom voltage in the fluctuation to 11.9V, then it would stay in alarm until acknowledged nearly.
My voltage is measured at GRT EFIS display #1, and due to the Schottkey diode (AeroElectrics Z-11), always shows less than 13.0 volts.

- Battery voltage checked fine (PC680 only 5 mo's old), as did field voltage at the Plane Power 60A alt, and supply voltage at the B+ terminal.
- Belt tension is fine per torque spec.
- I have tug-tested all wire connections, especially those at the Plane Power plug. No loose connections found.
- Had the alternator tested at a local alternator shop .... they found no problems.

Will now install a new 3-terminal plug a la Dan's discovery. Fingers crossed that takes care of the issue.
 
Recently, my low voltage light light began to appear frequently, on and off, for the better part of an hour. When I went to the EFIS engine page, the voltage was fluctuating up and down from 12.6V to 12.1. ( the alarm limit 12.0). No matter how long I watched, the voltage never stayed steady, it was constantly up and down across 0.5V spread, almost sinusoidal in pattern. I could see the alarm sound whenever the voltage dropped below 12. Turning on the boost pump dropped the bottom voltage in the fluctuation to 11.9V, then it would stay in alarm until acknowledged nearly.
My voltage is measured at GRT EFIS display #1, and due to the Schottkey diode (AeroElectrics Z-11), always shows less than 13.0 volts.

- Battery voltage checked fine (PC680 only 5 mo's old), as did field voltage at the Plane Power 60A alt, and supply voltage at the B+ terminal.
- Belt tension is fine per torque spec.
- I have tug-tested all wire connections, especially those at the Plane Power plug. No loose connections found.
- Had the alternator tested at a local alternator shop .... they found no problems.

Will now install a new 3-terminal plug a la Dan's discovery. Fingers crossed that takes care of the issue.

Set your alarm limit to 13 so you will be notified when the alternator fails. With it set at 12 volts, you are notified that your BATTERY is now at 25% and your safety margin is gone.

If my alternator fails and I see it at 13 volts, my battery will out last my fuel supply.
 
buss connection

Hi Terry

I had a very similar experience and replaced a perfectly good alternator only to find the real problem was a slightly loose screw securing the positive cable connector to the positive buss.

Worth checking.

Mike
 
Update

Put the bird back together and flew for 1.0 today. Charging system worked perfectly .... just like prior to the problem on 4/12. The puzzling part is why it's performing well. Here's the scoop:
- 60A PP alternator bench tested fine at the alternator shop
- I did not replace the Sumitomo 3 contact plug. I looked closely at both the new one I ordered and the one still on the airplane. I could see little benefit to replacing with an identical-in-very-way new plug. The prongs on the alternator were not corroded and looked fine, as did the plug's female sockets. Decided to reassemble and fly; if the problem was still there, THEN I would replace the 3-wire plug.
- tug tested all connections a second time... found nothing
- cleaned both pulleys with MEK to reduce the possibility of slippage
- carefully examined the existing belt ... looked fine
- put it all back together; tightened the alt belt to the same torque as before, 8 ft-lbs.

And today the previous problem was magically gone. That implies it was either a slipping belt or a flaky 3-contact plug (that worked fine when re-inserted). I'm betting it's the latter vs the former. :) Time will tell.
 
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