Name this electrical problem!

EvilEagle

EvilEagle

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EvilEagle
Airplane just came out of the annual and I noticed it was kinda hard to start occasionally, made some weird sounds but started every time. A couple of weeks ago I was flying to work and I noticed the volt meter was not at it's normal position (pegged at 15), it was about 13 and on the descent. I shut everything off and grabbed the handheld to get to work and back home that day. The A&P replaced the voltage regulator and had the alternator rebuilt.

I was flying to work this week and just happened to be looking right at the volt meter when it jumped from 15 to about 12.5 all at once. It stayed about the same for the rest of that flight. Flew it home the next day and was down to about 9 volts. I replaced the battery today but the volt meter never goes above 12.5. Is the Alternator out again? Voltage regulator? :dunno:
 
EvilEagle said:
Airplane just came out of the annual and I noticed it was kinda hard to start occasionally, made some weird sounds but started every time. A couple of weeks ago I was flying to work and I noticed the volt meter was not at it's normal position (pegged at 15), it was about 13 and on the descent. I shut everything off and grabbed the handheld to get to work and back home that day. The A&P replaced the voltage regulator and had the alternator rebuilt.

I was flying to work this week and just happened to be looking right at the volt meter when it jumped from 15 to about 12.5 all at once. It stayed about the same for the rest of that flight. Flew it home the next day and was down to about 9 volts. I replaced the battery today but the volt meter never goes above 12.5. Is the Alternator out again? Voltage regulator? :dunno:
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Could be a wiring issue, could be a grounding issue. Check all wires to the voltage regulator and alternator, check for corrosion on terminals. Also check switches and circuit breakers.
 
EvilEagle said:
Airplane just came out of the annual and I noticed it was kinda hard to start occasionally, made some weird sounds but started every time. A couple of weeks ago I was flying to work and I noticed the volt meter was not at it's normal position (pegged at 15), it was about 13 and on the descent. I shut everything off and grabbed the handheld to get to work and back home that day. The A&P replaced the voltage regulator and had the alternator rebuilt.

I was flying to work this week and just happened to be looking right at the volt meter when it jumped from 15 to about 12.5 all at once. It stayed about the same for the rest of that flight. Flew it home the next day and was down to about 9 volts. I replaced the battery today but the volt meter never goes above 12.5. Is the Alternator out again? Voltage regulator? :dunno:
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First of all, "pegged at 15" is way to high if that meter is anywhere near accurate. Should be more like 13.8-14 volts. Second your A&Ps approach (start replacing things until the problem goes away) isn't uncommon but often has a low success rate and can lead to serious amounts of wasted money and worse yet, can actually create more problems that it solves. Unfortunately it seems that only about 10% of the A&Ps actually understand electrical issues and know how to troubleshoot them. I strongly recommend you find one of the 10% before going any further.

As to trying to diagnose your problem(s) remotely, that could only be done if we know the make/model/SN and someone with the proper skills also has access to the appropriate diagrams. Even then it would require you (or your tech) to take measurements of the system in various states to produce any useful results.
 
I should have mentioned that my A&P took my alternator to a shop to have it tested, it checked bad and they rebuilt it.

This is all on a Glasair 1 FT with an O-320
 
EvilEagle said:
I should have mentioned that my A&P took my alternator to a shop to have it tested, it checked bad and they rebuilt it.

This is all on a Glasair 1 FT with an O-320
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Well, that adds a whole nuther question that needs to be answered first, what components does your charging system consist of?

As Lance said, diagnosing this over the internet isn't viable, all we can do on this is shoot the same shotgun your mechanic appears to be shooting. You really have to be there with a meter and work your way though the system and see what's not reacting properly and why.

As an aside, if your voltmeter is functioning properly you should have caught this problem before you fried whatever it is you fried. If you see 15 volts on your charging system, you have problems. Your systems static voltage is 13.2 volts, anything above that and you are charging. Lead Acid batteries do best when charged at 13.7-13.8 volts, although up to 14.2 volts is acceptable, though it will reduce the life of your batteries and require more frequent service with water. Most of the rest components in the system don't really like voltages above 14.5-14.8. I would be willing to bet that if you look at the specifications for your system that 15 volts is likely out of nominal range for operations beyond maybe the first few moments on a very low battery. The fact that your gauge "peggs" at 15 should have been an indicator to you that you were beyond nominal spec.

Just because you are in an experimental does not mean that you can do whatever you want. The FAA may give you all the leeway you want, but that holds no sway with the aviation gods. If you spit in the maintenance god's eye he will smite you mightily possibly with an electrical fire. You should not have been operating a "12v" airplane with a voltmeter "pegged at 15v". You have received your first and possibly only warning on this, so quit throwing parts at it and dig deep and find the root cause rather than just a "repair" where you don't know if you addressed the problem or not. This is the kind of stuff that you see in the small percentage of NTSB reports that are actually aircraft failure related.
 
Electrical troubleshooting actually is something I do very well. But as has been stated, it really can't be done over a message board. So I'll just ask some questions instead:

Have you (or your mechanic) checked the voltage with a known-good meter?

Have you checked the condition of the connections to the regulator (including the ground)? A properly-functioning regulator may produce an overvoltage condition if it's not detecting the voltage properly due to a poor connection, possibly caused by corrosion, etc.

Is there an overvoltage relay in the circuit? These will cut off the power to the alternator field in the event of an overvoltage condition, effectively "turning off" the alternator. But they usually are designed to reset once the aircraft is powered down.

Without being there and having diagrams (or knowledge) of the specific electrical system, those are the things I think I would be looking at first.

-Rich
 
Before we can debug, we need to better understand the layout/schematic of the electrical system.

A fairly typical setup would be like the Piper Cherokee's scheme...
http://www.needlescentered.com/images/cherokee180_Electrical.jpg

To me, it sounds like your alternator is tripping offline, leaving only the battery powering the electrical bus.

Unfortunately, there are lots of things that can cause the alternator to trip offline, and many mechanics just replace these items until the problem goes away.

  • Alternator main breaker
  • Field current breaker
  • Field current switch
  • Master bus switch
  • Bad voltage regulator
  • Bad Over Voltage regulator
  • Bad alternator
  • Bad/intermittent wiring between any of the above.
When I first got my Cherokee, it had an intermittent issue with the alternator tripping offline. Usually (but not always), cycling the field current switch would bring it back. Mechanics replaced alternators and voltage regulators without any success.

Eventually, I got involved and took a more systematic approach on the debug. It ended up being a combination of a bad field current breaker (exhibited resistance when pressure was applied to the case) and a intermittent/bad over-voltage regulator that was occasionally tripping offline at too low of a voltage (barely over 14 volts, when it should trip at 15 or 16 volts).

If you can reproduce the problem on the ground, then we should be able to debug the problem and find the bad element(s).

The first thing to do is a get a real voltmeter wired into the aircraft bus so that you can see/watch the bus voltage when the symptom occurs. This will verify that you do in fact have a problem (and not just a bad voltmeter in the plane).

After that, I would try wiring the voltmeter into the field current input to the alternator (at the alternator). You can watch the field voltage and see if it goes to zero or greatly reduces when the symptom occurs. If it does, the problem is somewhere in the field switch, breaker, VR, OVR, circuit and we can debug from there... If the field voltage remains about the same, the problem is likely with the alternator or the connections and breakers from the alternator back to the main bus.
 
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EvilEagle said:
snip of long sad tale... Is the Alternator out again? Voltage regulator? :dunno:
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Don't sweat it. I had a longer, equally sad tale when the alternator drive failed on the Dakota. Took about three weeks and $600 in parts to repair. Only $100 of that $600 was wasted...

Anyway, other folks have dodged around saying ya gotta take a systematic approach but they haven't helped by laying out that approach. Of course they don't know your system so they can't lay out that approach completely.

There are a few simple things to check. The simplest is to check the field wire for continuity and then check that it has voltage when the alternator should be energized. Another simple check is continuity of the load wire between the battery or bus and the alternator.

If the field wire is good and has voltage (prolly > 5 to 7 volts) then the alternator should generate electrons, assuming the alternator is good and grounded. If the alternator generates electrons then its up to the load wire (fat mother from alternator to bus or battery) to get them to the proper destination. There may be some sort of large diode between the load wire and its termination. I've heard those big diodes rarely fail. I know it's tough to get a valid test on one particular diode (happens to be mine) even though it is just fine. It's easy to take the big diode out of the circuit to test the system without it.

On a single, the charging systems are pretty simple. It does take some effort to dig up the schematic (or draw one) and figure out the test points. Then it usually takes an extra body to help test. A VOM is required and it helps to have some nice long jumpers with aligator clips. Be sure you don't accidently ground one of the aligator clips and let all the smoke out of the electrical system. New smoke is always expensive.
 
Thanks everyone for the things to check. (Didn't need the attitude adjustment though).

This electronic system is strange for sure, the day I bought it, the volts showed 15, and for the next year and 240 hours of flying it always said 15. Then these problems started.

My mechanic has the plane now, and he's going to work through it. I'm surprised at how quick guys are to judge both me and the mechanic... He's a thorough and well respected mechanic that has been in the business his whole life (dad was an A&P), and I'm a first time owner learning the ropes. Maybe I'll think twice about future postings... :rolleyes2:
 
EvilEagle said:
Thanks everyone for the things to check. (Didn't need the attitude adjustment though).

This electronic system is strange for sure, the day I bought it, the volts showed 15, and for the next year and 240 hours of flying it always said 15. Then these problems started.

My mechanic has the plane now, and he's going to work through it. I'm surprised at how quick guys are to judge both me and the mechanic... He's a thorough and well respected mechanic that has been in the business his whole life (dad was an A&P), and I'm a first time owner learning the ropes. Maybe I'll think twice about future postings... :rolleyes2:
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Actually, yes you did and from the sounds of it, still do. This isn't your car, you can't just pull over and get away from it when it starts burning.
 
I think it's funny how people talk down to others via the interwebs with no idea of someone's background. The man had a question about his aircraft. I think it is safe to assume he understands the consequences of a troublesome electrical system. I don't think he was looking for a moral lesson on flying aircraft with known malfunctions.
 
AWACSEng said:
I think it's funny how people talk down to others via the interwebs with no idea of someone's background. The man had a question about his aircraft. I think it is safe to assume he understands the consequences of a troublesome electrical system. I don't think he was looking for a moral lesson on flying aircraft with known malfunctions.
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I think you assume far too much, but I leave this conversation with a clear conscience and cede to his Darwinian rights. Flying around in an aircraft for a year with the volt meter pegged at 15 is just plain stupid and assuming that someone would do that understanding the potential consequences, well, that's beyond me. If he and you want to defend that, that is your prerogative, but realize it's defending stupidity, and aviation is unforgiving of stupidity. I don't give a damn about someones background. You come here and tell me a story that says "stupid", well, "stupid" crosses all other delineations of mankind.
 
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Instead of coming up with something witty to reply, I'm just going to see if the mods will lock this thread. Clearly it has gone from a question to an insult session. Awesome work Henning! I'm sure this will encourage others to post questions and seek advice. :rolleyes2:
 
You haven't mentioned what the "weird sounds" were that you heard... can you elaborate on that? Were they coincidental to actions you'd take?

Don't leave the thread; you took action when you saw something out of the ordinary. I don't see you as "stupid". You may just now be learning that 15V is not "normal", but that's what you've always seen, were used to, and may just now be learning isn't normal. Glad to hear you've got a mechanic looking at it before you fly again.
 
TangoWhiskey said:
+1 :thumbsup: :rofl: That's a rule of thumb I can remember!!
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I beg to differ. The "normal" position of the analog differential pressure gauge that's the display for my "Lift Reserve Indicator" is indeed "pegged" (in fact it's pushing so hard against the peg the needle is noticeably curved) when in cruise flight. I guess that's just consistent with the notion that there's an exception to every rule.:D
 
gismo said:
I beg to differ. The "normal" position of the analog differential pressure gauge that's the display for my "Lift Reserve Indicator" is indeed "pegged" (in fact it's pushing so hard against the peg the needle is noticeably curved) when in cruise flight. I guess that's just consistent with the notion that there's an exception to every rule.:D
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I also like to see my fuel indicators pegged! But it doesn't stay that way very long.
 
gismo said:
I beg to differ. The "normal" position of the analog differential pressure gauge that's the display for my "Lift Reserve Indicator" is indeed "pegged" (in fact it's pushing so hard against the peg the needle is noticeably curved) when in cruise flight. I guess that's just consistent with the notion that there's an exception to every rule.:D
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The gauge is insufficient for the job.

Like four red on the PAPI you know your low but it really doesn't tell you that much. At limit or more for normal is a problem.
 
RMCN172RG said:
The gauge is insufficient for the job.
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Actually it's (marginally) sufficient for it's intended function which is to indicate how close you are to the critical angle of attack in situations where that matters. When the gauge is pegged is simply means that you'd have apply enough g force to rip the wings off before you could cause a stall. And since I'm generally not gonna pull that hard, the actual AoA which would tell how many excessive g's you could generate if the wings stayed on, isn't of much concern.
 
EvilEagle said:
Instead of coming up with something witty to reply, I'm just going to see if the mods will lock this thread. Clearly it has gone from a question to an insult session. Awesome work Henning! I'm sure this will encourage others to post questions and seek advice. :rolleyes2:
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Why would it get locked? Just because you don't like what you're hearing doesn't mean it violates the terms and conditions of this board. It's not an insult session unless you perceive it as one. It's honest, maybe too honest for some egos, but all truth. You can either look at it and rationalize your actions and get mad, or you can look at it and realize "s-t, I got lucky" and learn more about the systems that are vital to safe operation and start paying attention to them before they get you and your passenger killed.
 
Just a comment on Henning's explanation.

When a young pre-checkride pilot posted about a training flight that had a questionable element, the young pilot got the message, dug into the topic in question, and came back with an appreciation for the matter. As fellow pilots we really couldn't ask for much more (other than the young pilot's CFI to do a better job).

Now we have a seasoned aviator pushing back on learning an aircraft system. Many of us are in a bit of shock because we take learning our systems quite seriously even if they are simple systems. Okay, some folks have been a bit rough, perhaps 'cause they know the seasoned aviator is trained to a very high standard.

I'm of the opinion that none of this is really personal even though it is very easy to take it that way. A question has been asked and a shotgun blast of replies have questioned an A & P's competence and a pilot's system knowledge. Maybe it's time for the seasoned aviator to say something along the lines of: sheesh, some of those comments left a mark but yup, I need to know more 'bout my ride and it is up to me alone to do that.

Of course maybe this is all just Saturday morning pointless rambling...
 
Or it could be time to offer up suggestions on how to fix the problem and leave the "moral" lessons to the aviation gods, or the FAA, whichever deems it appropriate to intervene.

/SARCASM/ Of course, there are those among us that would NEVER do anything questionable or anything that would cause another person to even raise an eyebrow. After all, we ARE pilots and thus incapable of error. Anyone who should commit error is
just a lesser being./SARCASM/
 
WHEN I bought my double runout Seneca II, Concorde AXC35's was clearly the battery of choice, even in 1998 when it was brand new.

I read the ICAW's and the engineering specs, graphs, had my VR's adjusted to 13.8 on a 58 degree day. That leaves 3% of the capacity unused and vulnerable to sulfation.

So the fix for that was for the battery to sit on a desulfator anytime it's in the hangar- the floating point there is 14.2 at 40 mah.

I do think that Henning is correct that 15V pegged for a year is a boiled battery, maybe even an exploded battery under lots of load. Like Sanchez says about operations, it's amazing what many pilots don't know about systems and it's amazing that we don't have more fatalities therefrom.

Here's a P-Baron that came to grief from failure of the owner to understand electrics....the operator has left aviation.
 

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I think Eagle was justified in asking the question on the board. I also don't think that I would have thought that 15V on the meter was a big deal if it had been that way since I bought it. I'd have even less faith in the meter since its a homebuilt bird.

I guess I don't really get all the bashing that's been going on.

I'd have to say that the pilot education curriculum provides absolutely zero help when it comes to identifying problems. In my training it was basically limited to 2 items: 1) If the prop stops, you have a problem, land immediately; 2) If something doesn't seem right land immediately. However, there was really no discussion of how to decide when something wasn't right.
 
COFlyBoy said:
I guess I don't really get all the bashing that's been going on.
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I do, because I often see it happen, but I think it's counterproductive. If we want people to come forward with stories and questions so we can all learn something we can't jump all over them then expect other people to put themselves in the line of fire with their own questions. There are ways to tell people that they are wrong without trying to make them feel like idiots, especially in public. That's why safety reports are non-punitive. People won't come forward if they think they will be punished. We here on this board can't take certificate action like the FAA or fire people like your boss can, but we can be punitive with some of the public shaming that happens sometimes.
 
COFlyBoy said:
I think Eagle was justified in asking the question on the board. I also don't think that I would have thought that 15V on the meter was a big deal if it had been that way since I bought it. I'd have even less faith in the meter since its a homebuilt bird.

I guess I don't really get all the bashing that's been going on.

I'd have to say that the pilot education curriculum provides absolutely zero help when it comes to identifying problems. In my training it was basically limited to 2 items: 1) If the prop stops, you have a problem, land immediately; 2) If something doesn't seem right land immediately. However, there was really no discussion of how to decide when something wasn't right.
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I'm sorry you had such poor training. I still don't understand how someone can just accept a gauge reading that is outside parameters just because "That's the way it's always been". When things on an airplane aren't right, you fix them. Regardless if it's the gauge or the system, the problem should be rectified.
 
bbchien said:
WHEN I bought my double runout Seneca II, Concorde AXC35's was clearly the battery of choice, even in 1998 when it was brand new.

I read the ICAW's and the engineering specs, graphs, had my VR's adjusted to 13.8 on a 58 degree day. That leaves 3% of the capacity unused and vulnerable to sulfation.

So the fix for that was for the battery to sit on a desulfator anytime it's in the hangar- the floating point there is 14.2 at 40 mah.

I do think that Henning is correct that 15V pegged for a year is a boiled battery, maybe even an exploded battery under lots of load. Like Sanchez says about operations, it's amazing what many pilots don't know about systems and it's amazing that we don't have more fatalities therefrom.

Here's a P-Baron that came to grief from failure of the owner to understand electrics....the operator has left aviation.
Click to expand...

I don't see a problem with this plane........:dunno:
It does look like the owner spend alot of money on those newfangled Q tip props though.. :D:D:D:cheerswine:
 
The OP said the A&P rebuilt the alternator and replaced the voltage regulator. If the regulator was new and not badly out of the spec and the voltmeter still read 15 volts, then the voltmeter is likely out of whack.

As for the continuing failure, there are some small things that can do this. If an overvolt sensor has a loose ground connection it will trip at odd times. If an electronic voltage regulator is present it will be sensitive to any RF that gets into the aircraft's wiring. The sense circuitry inn the VR needs only microamps for its readings and if one of the Com antenna cables has a dirty/loose/corroded shielding ground at either the radio or antenna, RF escapes and generates voltage spikes in the aircraft's systems, and can trip the VR offline. Spent a week chasing that one in a 185. Key the mike, alternator fell offline. Finding the mike/alternator failure correlation was the key to solving the problem.

Dan
 
Henning said:
I'm sorry you had such poor training. I still don't understand how someone can just accept a gauge reading that is outside parameters just because "That's the way it's always been". When things on an airplane aren't right, you fix them. Regardless if it's the gauge or the system, the problem should be rectified.
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I don't think the OP ever suggested that it was outside parameters. My point was that there was probably nothing that suggested that the reading was an issue. He didn't say if the 15V was past a redline.

I just checked the POH for my Cherokee 6 and there is nothing that states what the upper limit is for the voltage. We only have an ammeter though, so there'd be no way to know if it was over charging. In the POH it calls it a 14V system.

The troubleshooting training I got covered everything that is listed in the POH. It did not go into the tribal (read A&P) knowledge required to troubleshoot a minor (and possibly intermittent) issue.
 
COFlyBoy said:
I don't think the OP ever suggested that it was outside parameters. My point was that there was probably nothing that suggested that the reading was an issue. He didn't say if the 15V was past a redline.

I just checked the POH for my Cherokee 6 and there is nothing that states what the upper limit is for the voltage. We only have an ammeter though, so there'd be no way to know if it was over charging. In the POH it calls it a 14V system.

The troubleshooting training I got covered everything that is listed in the POH. It did not go into the tribal (read A&P) knowledge required to troubleshoot a minor (and possibly intermittent) issue.
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That was the point of my first post to rectify the lack of knowledge that 15v is outside of parameters for a 6 cell system. The fact that your CFI did not cover this in the "systems" part of your training only shows that he didn't have this knowledge or assumed you already did. To say this is "A&P" level knowledge is just plain not correct, this operational level knowledge. Because your aircraft does not have a voltmeter does not mean it is unimportant information. Just because there is information that has not been fed to you does not mean it is outside the purview of what you as a pilot should know, especially an owner/pilot. Do you "need" to know it to fly? No, you don't. The more knowledge you have as an owner though, the less cost intensive your ownership experience will be. The more knowledge you have as a pilot, the more likely you will be to catch a problem in its infancy and land on a runway rather than a hillside.

You can defend ignorance in the name of "I wasn't taught that" to your hearts content, doesn't change the results of ignorance any though. Aviation is a heartless mistress.
 
COFlyBoy said:
I don't think the OP ever suggested that it was outside parameters. My point was that there was probably nothing that suggested that the reading was an issue. He didn't say if the 15V was past a redline.
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In the first post he said it was pegged. I still stand by a Pegged meter or a bent needle, except for measuring excess lift, is not normal.

A pegged full gas guage is OK too.
 
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Henning said:
That was the point of my first post to rectify the lack of knowledge that 15v is outside of parameters for a 6 cell system. The fact that your CFI did not cover this in the "systems" part of your training only shows that he didn't have this knowledge or assumed you already did. To say this is "A&P" level knowledge is just plain not correct, this operational level knowledge. Because your aircraft does not have a voltmeter does not mean it is unimportant information. Just because there is information that has not been fed to you does not mean it is outside the purview of what you as a pilot should know, especially an owner/pilot. Do you "need" to know it to fly? No, you don't. The more knowledge you have as an owner though, the less cost intensive your ownership experience will be. The more knowledge you have as a pilot, the more likely you will be to catch a problem in its infancy and land on a runway rather than a hillside.

You can defend ignorance in the name of "I wasn't taught that" to your hearts content, doesn't change the results of ignorance any though. Aviation is a heartless mistress.
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I'm still thinking the OP did it right. He said this doesn't look right and asked about it. Not sure why all the hatin'.

Second, in my first post I said that generally flight training does not cover stuff outside of the POH, and doesn't go into detail on how to troubleshoot issues. Though, in this case the OP does have a million $ flight education (just in a much bigger, faster, louder and more expensive airplane).

Never said I didn't know it, just that I wasn't taught it in flight training. I've got me technical skillz like you wouldn't believe.
 
I think maybe I was interpreting pegged to mean pointing straight at 15V and never moving as opposed to actually sitting on the peg. Don't most VMs go higher than 15V?
 
COFlyBoy said:
I'm still thinking the OP did it right. He said this doesn't look right and asked about it.
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Really? Sounded to me like he had two system failures in short order after watching the gauge read off the scale for as long as he's owned the airplane and is now trying to figure out why it failed the second time.
 
EvilEagle said:
I should have mentioned that my A&P took my alternator to a shop to have it tested, it checked bad and they rebuilt it.
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Let's talk about some stuff here.

1. If the OP had actually been flying with the electrical system at 15 volts for a year or so, he would have gone through a few dozen batteries and a tank car full of water.

2. He was looking at the voltmeter when it "suddenly" jumped from 15 to 12 volts and then down to 9 volts. Electrical systems don't work that way. Defective voltmeters DO work that way.

3. "The alternator tested bad." I hate the word "bad". Does "bad" mean that the paint was scratched? Or that a 60 amp alternator only put out 59.99 amps? Or that one phase was dead? What does "bad" mean and what does "rebuilt" mean? Is a "fixed" alternator "rebuilt" and why should an alternator that has failed get "rebuilt" rather than "fixed"?

4. Why would the A&P replace both alternator and voltage regulator at the same time? THe odds of them both failing simultaneously is about the odds you would get arguing with an umpire. Or your wife.

5. So you replaced the battery, your A&P replaced the alternator and VR. My best guess leaves you about $500 in the hole and with the same problem. :idea:

6. Do yourself a favor and go down to Harbor Freight (or Radio Shack) and splurge $50 on a decent voltmeter and do an hour's troubleshooting instead of doing what the biz calls "shotgunning". Shoot enough parts at the problem and eventually you will hit the defective part ... if you don't break something else in the process.

7. You've got an experimental. That gives you a lot of leeway to do some learning. You've got to have an EAA chapter near you. Somebody in that chapter must know which end of the soldering iron gets hot. Ask that person to show you how to troubleshoot the problem.

Jim
 
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