Electrical System Troubleshooting Guide

Discussion in 'Maintenance Bay' started by hamer, Jan 8, 2019.

  1. hamer

    hamer Pre-takeoff checklist

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    I'm having some issues with my electrical system, and I'm curious if there is a troubleshooting guide I can follow. I'm looking for step by step, "clamp multimeter here, measure X."

    My battery dies after about 20-30 min in flight. My load is relatively low, 5-8amps (radio and transponder), seems to be either the generator, or voltage regulator that's the issue. Here's my setup:

    Engine: O-290-D
    Generator: Delco Remy 14V/20A
    Voltage Regulator: Unknown, photo attached
    Battery: Gill G-25

    1) How do I measure the voltage/amp output of the generator individually?
    2) How do I measure the voltage/amp output of the voltage regulator?
    3) With nothing on, engine running, my amp meter goes negative with higher RPM, and goes more positive as I turn things on, is it wired incorrectly?
    4) At 2000RPM the amp meter reads ~12.5A, this hints to me that it's either the voltage regulator or generator (should be 20A).
    5) With nothing on, at 2000RPM, volt meter increases to just above 14V

    I've had a lot of people tell me to check this or that, but I don't know exactly where to connect leads and what the measurements should read. Yes I will be getting my A&P involved, but I would like to do my due diligence first.

    Thanks for the help.
     

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  2. Bell206

    Bell206 Line Up and Wait

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    FYI: there are a number of existing threads on POA that cover, in detail, the issues you are experiencing. I've found it's best to start at the easiest point first: verify you have a good battery first and that check is found in the battery manual.
     
  3. hamer

    hamer Pre-takeoff checklist

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    I just got done reading 8-10 threads. Most go about the same way, check this or that without much detail on where the measurements should be made. Just looking for a little more detail/photos.
     
  4. Chip Sylverne

    Chip Sylverne En-Route PoA Supporter

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    Fear is the poison of our lives.
    Google "Lucas generator and control box tests". Best Genny troubleshooting guide I have ever comes across. If you can't find it, send me a pm with a real email addy and I'll send you a .pdf.
     
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  5. weirdjim

    weirdjim En-Route

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    if you don't argue with me, I'll try to help.

    1. Get yourself a Harbor Freight $10 multimeter.
    2. Measure the battery voltage at rest (engine off). Put the black lead to the metal airframe, or if a toothpicks/tissuepaper machine, to the NEGATIVE lead of the battery. Red lead to the POSITIVE lead of the battery. Record voltage. Report back here. (should be +12 volts or a bit higher)
    3. Start the engine. Leave the voltmeter connected as in (2). Run the engine up to about 2K RPM. Record voltage. Report back here. (should be 13.5 volts or a bit higher)

    To be continued.

    Jim
     
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  6. hamer

    hamer Pre-takeoff checklist

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    Jim,

    Thanks for the help, here are the results:

    Master off: 12.30V
    Master on/engine off: 12.21V
    Engine 1000RPM: 12.10V
    Engine 1500RPM: 12.63V
    Engine 2000RPM: 14.58V
     
  7. weirdjim

    weirdjim En-Route

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    Ah, a man after my own heart. I had a C-120 (N2014V) for the first five years of my aircraft ownership years. Nobody told me I couldn't reupholster the airplane or paint it with automotive paint, so I did so. That was some LONG years before I had my A&P (not to mention my IA) and hopefully the statute of limitations has run out. Also, nobody told me you don't take a C-85 120 from San Diego to Boston, so I did. Unfortunately, nobody also told me you don't fly that airplane 8 hours a day without earplugs or headphones, so I was honestly deaf for an hour in the afternoon for four days going and four days coming. HUH? WHAT DID YOU SAY?

    Nice little airplane.

    Now back to it.

    We can worry about the 2K RPM at 14.6 for later. Now start throwing a load on it at 2000 RPM. Radios, lights, whatever else you have. You say your aircraft ammeter shows a NEGATIVE charge when you run the engine up and that negative charge goes DOWN as you load up the aircraft electrical system with loads. If I read that right, your ammeter is in the circuit backwards. Simply take the two leads off of the back of the ammeter and reverse them. The ammeter should show POSITIVE charge when the engine comes up to speed and drop off a bit as the loads are put on.

    Engine RPM 2K, voltage about 14.6 no load. Throw a heavy load on it. Landing lights should work. Take a voltage measurement every minute for five or ten minutes and report back. An approximate ammeter reading (after you fix it) would help.

    Jim
     
  8. Timbeck2

    Timbeck2 Final Approach

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    14.5 sounds a bit too high

    I'm going to shut up and read. This is good stuff Jim
     
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  9. JAWS

    JAWS Line Up and Wait

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    Maybe I missed it, but what make and model of aircraft is experiencing the problem?

    Edit - I did miss it. Please disregard the above DAQ!
     
  10. hamer

    hamer Pre-takeoff checklist

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    This is my first airplane, I love it. This electrical problem has been a little bit of a bummer since I just got the plane and it's grounded me, but going through the troubleshooting and trying to figure things out has been alot of fun. Thanks for sharing your story.

    I didn't have alot of time to do the full test at the airport today, but I did a quick one. I'll do a longer test tomorrow and see if time becomes a factor:

    Engine 1500RPM (everything on except radio ~10A): 12.14V
    Engine 2000RPM (same load as above): 13.15V

    It does appear to be working, but again need to test over time. What worries me is that the battery starts to fail after 20-30min at cruise, where I should have full generator output. It does also happen when I'm going touch and goes, but I spend a lot of time at idle coming down to land.

    I'll make sure I get the ammeter wiring fixed, it's been a little confusing with it backwards.

    Thanks again for the help Jim.

    I never explicitly mentioned it, but it is in my signature :)
     
  11. Lantraxco

    Lantraxco Pre-Flight

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    14.6 sounds fine to me, not outside the limits of sanity. I would double check that the battery is installed and connected with correct polarity, though I should think something would be letting smoke out if the polarity is reversed. lights, starter and believe it or not some generators won't care about polarity. Radios usually do rather aggressively though... don't ask me how I learned that as a teenage gearhead.
     
  12. Dan Thomas

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    I'm wondering if the commutator in the generator is shot. If it wears out-of-round, the brushes start bouncing at higher RPM and the output falls off.

    A battery connected backwards would be toast real quick. And the generator would suffer enormously.
     
  13. Tom-D

    Tom-D Taxi to Parking PoA Supporter

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    When looking at the picture in the first post I see several discrepancies.
    I'd start by replacing the old vibrator voltage regulator, (they have a habit of heating during flight and quitting) and replace it wit a new electronic type.
    next I'd disassemble every electrical connection in the circuit and clean them.
    You've shown us that the charging circuit is working, but when you fly it isn't working long term. To me that is usually a heat caused problem, and those old vibrator regulator are famous for it, speciality when they have dirty connections.
     
  14. weirdjim

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    OK, so we now know that the generator/regulator is doing its job on the ground. Now it is time to do the troubleshooting where the problem is. For this you will either need to buy or make a fused extension cord. You can buy an inline fuse holder from any auto parts store. Fuse size doesn't matter ... I'd use half an amp or so. Or you can make a blade fuse holder out of some .187" faston crimp terminals. SECURELY hook the voltmeter to this FUSED extension cord.

    What we are trying to do is measure the bus voltage in the air while you are flying. The problem is that a C-120 shakes around like a double-jointed hooker on dollar night and we don't want our measuring device to short out and cause a fire. That will solve the problem, but probably not the way you intended. Find somebody on the field that knows what they are talking about and get them to show you how to do it safely.

    What I want to know is whether or not the loss of voltage over flight time is slow --- that is, the voltage slowly drops which indicates a thermal problem or it drops over a short period of time, like less than a second, which indicates a dirty contact SOMEWHERE. Either one is going to be a pain in the @$$ to solve but we have to start somewhere.

    By the way, do you have a shop nearby that specializes in electric motor repair? They will probably be the only place you will be able to get an old generator cleaned up and (if necessary) rebrushed and have the commutator turned if necessary. As to the voltage regulator, Tom is right. Those old buggers are prone to thermal ju-ju. Whether or not said electric motor repair shop has somebody old enough to remember how to fix that old regulator is a question I can't answer. But there ARE modern transistorized regulators that you can use.

    As I vaguely remember the 120, the generator/regulator was made by one of the GM companies, Buick comes quickly to mind. I see you making friends at the local antique car clubs in your future.

    Electrics from Buick, carbs from Marvel, mags from Ford 8/9N tractors ... ah, those were the days.

    Jim
     
  15. Dan Thomas

    Dan Thomas En-Route

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    I've never seen an electronic generator regulator. Lots of electronic alternator regulators, which aren't the same thing at all. In airplanes, generators were abandoned in the the 1960s. Is someone building an electronic regulator for generators now?
     
  16. mondtster

    mondtster Pattern Altitude

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  17. Ray Eaker

    Ray Eaker Pre-takeoff checklist

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  18. weirdjim

    weirdjim En-Route

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    Now I would NEVER recommend an automotive part for an airplane, but I've got this friend Ernie ... that sells regulators for antique vehicles ...
     
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  19. weirdjim

    weirdjim En-Route

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  20. Dan Thomas

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  21. hamer

    hamer Pre-takeoff checklist

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    Thanks everyone for the input. I will do some more debugging and report back with the results.

    That regulator looks nice, however at ~$250 without the C120 on the AML (meaning I'll need a field approval) + whatever I'll have to pay to repair/replace the generator, it's looking like doing an alternator conversion is just the best way to go. The B&C kit is $700 and comes with everything I need and pretty much all the labor involved is the same as repairing the current system. My original choice was to just do the alternator conversion, however the FSDO is closed because of the shutdown and I was hoping to at least get back in the air in the meantime.
     
  22. weirdjim

    weirdjim En-Route

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    Son, you need to sit down with an IA who either has gray or no hair and discuss the fine points of keeping a 70+ year old airplane in the air without making the paperwork weigh more than the airplane. If I am not mistaken, the B&C has a disclaimer that they are meant for experimental aircraft only, unless they have something new I haven't seen yet.

    Jim
     
  23. hamer

    hamer Pre-takeoff checklist

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    I do need to find a good IA, just haven't been in ownership long enough yet. The B&C kit is a pully, but so it my current generator.
     
  24. Let'sgoflying!

    Let'sgoflying! Touchdown! Greaser! PoA Supporter

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    Does this mean we won’t find out what your problem actually was? :(
     
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  25. Tom-D

    Tom-D Taxi to Parking PoA Supporter

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  26. weirdjim

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    Read 21.303 (b)(2) and see if you can find the FAA General Counsel's opinion on this section. It is a godsend for old/antique aircraft.

    Where are you? I see it says socal but that is from the Tehachapis to the Mexican border. Maybe I know a good IA that knows how to maintain older airplanes.

    Jim
     
  27. Tom-D

    Tom-D Taxi to Parking PoA Supporter

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  28. hamer

    hamer Pre-takeoff checklist

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    Link? Google is failing me.

    I am based out of KSNA. I may have found someone today that can help me, but I'm always willing to take more recommendations if you know someone.

    I will read 21.303 tonight and see what I can find.
     
  29. weirdjim

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  30. weirdjim

    weirdjim En-Route

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    Ooooh, the high rent district.

    Jim
     
  31. Chip Sylverne

    Chip Sylverne En-Route PoA Supporter

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    Fear is the poison of our lives.
    • Opening the regulator up, cleaning the contacts, setting the air gaps and adjusting the cut-out ain't rocket surgery. Most of them are set to the thickness of a business card, but specs are available. I'd refer you back to the Genny manual I suggested earlier. If you understand how they work, they are very simple to repair. In most cases, cleaning nd adjustment do it. I've done it on about every tractor I own, Delco and Lucas.
    Just sayin'
     
    Last edited: Jan 9, 2019
  32. hamer

    hamer Pre-takeoff checklist

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  33. hamer

    hamer Pre-takeoff checklist

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    I opened it up last night and it looked brand new inside. I will try to adjust it later this week when I make it back to the airport.
     
  34. Tom-D

    Tom-D Taxi to Parking PoA Supporter

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    that's great, it comes with paper.
     
  35. Chip Sylverne

    Chip Sylverne En-Route PoA Supporter

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    Fear is the poison of our lives.
    Look for crud on the contacts, and on the cutout. If all that's clean like new, then somebody's been chasing his problem. Might then be time to have a look at the brushes, commutator, etc. I hesitate to say this, but you have cleaned all the airframe, engine and battery grounds, RIGHT?
     
  36. Tom-D

    Tom-D Taxi to Parking PoA Supporter

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    NAPA.
     
  37. Chip Sylverne

    Chip Sylverne En-Route PoA Supporter

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    Fear is the poison of our lives.
    And for grins, you might check the condition of the harness and slap an ohm meter on the wire between the field terminal of the regulator and the Genny and do some wiggling to see if there may be a problem there. And see that the regulator itself is well grounded.
     
  38. weirdjim

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    Come on, folks. We are SEWAGGING and RECTORANDOM troubleshooting here. Lets get some data before taking off on a wild goose chase.

    Jim
     
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  39. Dan Thomas

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    Maintenance poker. Each is hoping his opinion is right and will win the hand. It's the best most here can do without actually being there and troubleshooting it ourselves.
     
  40. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser!

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    For once, I am going to have do disagree with you Mr. Thomas.
    The old 40's 50's vintage generators /regulators / starters would work just fine hooked up either way. My first car was a '59 Sunbeam Alpine that, like a lot of English junk, was built with a positive ground system. When I bought it, a previous owner had taken it to Sears and they had installed the battery with a negative ground configuration - like a "normal" car. Everything worked fine - and had been working that way for some time. Even the two speed (off and on) electric windshield wipers worked (there was no radio). I re-did things back to the original positive ground just because it seemed to be the right thing to do.
    Now, a "modern" alternator, or electronic regulator, or radio, or... won't work and you will likely end up with an expensive repair bill. But in any case, that doesn't seem to be the problem with the O.P's aircraft.