High Amps 1977 Turbo Arrow III

Hello all,

I have been experiencing a high amp reading in my plane. This has occurred every time I have flown it. The readings are all over the place. Sometimes normal and other times super high (one time as high as 50). Electronic use is normal with an all Dynon panel. Turning on the landing light will cause a significant rise in the reading. The battery is about one year old.

So far, the problem is a mystery. Any help is greatly appreciated.




  • After recharging the battery the current should definitely level out to match the load.

    Some of the high current items:

    1) Fans such as a cabin fan

    2) Pitot heat

    3) Prop heat

    4) Lighting usually be in the 10 Amp range for Halogen landing lights per light.

    5) Landing gear motor

    This is worth isolating. It could be a false reading but it could also be a poor connection that might overheat even more on you.

    One culprit for retractable gear planes is the emergency gear down valve. If it leaks at all (internal so no external leak) then the gear motor will continuous run trying to keep the gear up. You may not hear it in flight and there is no light for when the pump is on. This type of problem can be intermittent too. One key clue for this is if the high current draw is only in flight (with the gear up) and never on the ground.

    Eric Panning
    1981 Seneca III
    Hillsboro, OR (KHIO)

  • Hi Todd,

    First off, big congratulations on retiring your low-RPM vibration problem!!

    As far as your high-current reading goes, there are three potential root causes that come to mind.

    1. Failure of the current sense causing an artificially high (or intermittent) reading on the current meter. Most of our planes were originally shipped with a panel meter having an internal sense resistor. Sometime in the early 80s it was realized these meters fail OPEN, leaving the pilot with no charging system and a potential in-flight emergency. An AD was issued, replacing the meter with about a foot of #10 wire, across which was connected a generic voltmeter, calibrated in amps. If the ring terminals on the #10 become loose or corroded, the voltage drop will increase (or become intermittent) increasing the reading on the current meter. Same is true for new digital engine monitors, since the avionics shop will install a shunt right where that #10 wire was.
    2. Failure of the voltage regulator, potentially also intermittent. The output voltage of the Arrow's alternator (believe it's an ALX-9525BR, but don't quote me on that...) is held constant by adjusting the field current so that the bus input to the regulator maintains 14.2 volts. When those regulators fail, they usually deliver a continuous 3 amps into the field windings, and since your alternator has a current gain of about 20, you'll get a reading of roughly 60 (3x20) amps on the ammeter. At the same time, the output jumps to about 16.5 volts, which drives most of the 60 amps into your battery, rapidly overcharging it. That's why Lamar included an over voltage relay between the bus and the regulator, to prevent an in-flight battery fire.
    3. Inappropriate current consumption by a malfunctioning appliance. Eric's suggestion of the landing gear is a great example.

    To isolate the cause, recommend finding a way to reproduce the problem on the ground, where troubleshooting is both easier and a whole lot safer. Since you'll need to get above 1800 RPM for the alternator to make 50 amps, please find a place where you won't scratch up that brand-new prop! Suggest using a pair of handheld meters, rather than the panel mount instruments, even if they are new digital units. Home Depot has a Klein Hall-effect current meter that's great for debugging alternators.

    Going down the list, if your hand-held current meter matches the panel meter (showing the 50 amps, etc), then you can rule out cause number one. If the hand-held voltmeter shows your bus is maintaining a solid 14 +/- 1/2 volt, your regulator is fine, and you've now eliminated option two from the list. At that point you can power down individual systems (by switch or by breaker) to see which one eliminates the 50 amps.

    If you absolutely can't reproduce the problem on the ground, suggest recruiting a helper to monitor the meters in flight, while you PIC the test. The remainder of the checklist is unchanged.

    Good luck,


  • Adding to Bob's comments. Do you have voltage and current data from the engine monitor or Dynon? This can be very helpful for troubleshooting.

    Also, what is the system voltage when current is high? If you don't have it on one of the displays then a 12V cigarette lighter plug with a voltage display can be very helpful.

    Target voltage and high current means it is either reading wrong or going somewhere. High voltage and high current means the system is trying to "stuff" it into the battery. Regulator issues as Bob outlined above.

    although you can check every breaker I would check the big loads first.

    For the vibration issue, can you describe again what you found in pre-flight and what they determined was wrong with the prop? How much play was in it? Was it in the plane of rotation, fore/aft, or ? Did they think it was because of the play or track?

    Todd, I seriously think this thread and your determination has driven a key outcome. Lot's of great ideas from everyone on what to look for and your excellent follow up on what was actually found. Your efforts will save fellow pilots $10's of thousands in troubleshooting related expenses as well as all the downtime. Thanks again!

    Eric Panning
    1981 Seneca III
    Hillsboro, OR (KHIO)

  • Thank you for all the amazing suggestions. I will definitely be using info in this thread to troubleshoot the issue. As I have answers I will post here.

    I will be at the airport early next week to start troubleshooting.

    Much appreciated.


  • As for the prop issue. The vibration occurred when rpm's dropped below 900 or so. There was never an issue in flight. The prop was installed in 2008 and had never been serviced. Total time on the prop was around 600 hrs. The head mechanic actually grabbed the prop about in the middle of the blade and pushed and pulled back and forth creating a click sound. As if had a little bit of play.

    Initially when disassembly started, it was noted that there was a red dye oil leak present. I will contact the prop shop next week and get the report on findings prior to the repair. I'll post findings.


  • Update:

    I flew the Arrow today to check on the new prop and the high amp issue. The prop is smooth and the previous vibration issue is much better at idle, climb out and cruise.

    The high amp issue surfaced again and here is what happened. After start up the amps were as high as 50. Shortly after it dropped to around 30. Avionics and strobes were the only systems on. At climb out after the gear up switch was engaged the amp reading went up to 50+ while the gear was coming up. A warning was then announced from the Dynon HDX Skyview. Amps then dropped back down to 30 after.

    About 20 minutes later on my way back, I lowered the gear and the amps went up again. In addition to this a bunch of red x's appeared with a back background across all engine monitoring gauges on the sky view. I also didn't feel the gear coming down. I ended up switching the alternator to off then back on and the x's went away and all gauges reappeared. The gear was down and we landed without incident. One correction regarding the battery, Turns out it was installed June '23.

    So the mystery continues.🤪

  • Todd, were you able to monitor bus voltage throughout the test flight? Bob

  • Unfortunately no.

    One question I haven't figured out is what is an acceptable amp draw for a PA28R-201T With two Dynon HDX Skyviews. And with active landing gear activated and in transition.

    I'm going to troubleshoot tomorrow

    Thanks everyone.

  • That's a beautiful setup you've got.

    The Dynon installation manual provides power consumption specifications in Chapter 2: System Planning. The individual displays are about 2.5 amps each, with the exact rating serial number dependent. With the exception of the AOA heater and the radios in transmit mode, everything else is flea power. Altogether, with the AP running, maybe 10 amps for the entire system.

    The gear pump in my Seneca peaks at 17 amps while cycling on jacks. The inline breaker is rated at 25 amps.

    Once the battery recovers from engine start, and the landing lights and pitot heater are off, figure 10 amps continuous and a max of 30 while the gear runs.

    BTW, I believe the Dynon is continuously storing the status message with bus voltage and current, to its internal hard drive. If you download that file to a USB thumb drive, and read it with excel, you can probably figure out what's going on pretty quickly.

  • Great info! I'll definitely look into the possibility of the Dynon storing info. I checked the specs and with the backup battery the Skyview is 5 amps draw.

  • I still think it is gear related. It is just about the only device in the plane to draw high amps aside from prop and pitot heat.

    Another thing to check is the battery connections as well as the voltage regulator connections. If the regulator sense circuit has resistance then you will get excess current (and high voltages). also look for issues with grounds.

    Eric Panning
    1981 Seneca III
    Hillsboro, OR (KHIO)

  • My mechanic pulled the battery yesterday to bench test it. It was only registering 10.5 volts. He charged it for a few hours and it was back up to a normal range. And of coarse it was quitting time on Friday.

    He is going to check it Monday morning to see if it lost any charge. If not reinstall and run the engine and check readings. He also plans on jacking it to cycle the gear.

    I'll let you know the findings.


  • Ok, that is why the voltage measurement is so important.

    You should not charge this battery - should throw it away. 10.5 is beyond dead - you likely have a shorted cell. The alternator was struggling at max current to try and reach ~ 14 volts but with the shorted cell the battery is fundamentally unable to reach this voltage.

    If a lead acid aircraft battery ever reaches this low of a voltage it should always be replaced. The next failure modes are overheat/explosion, short, or open - all of them catastrophic.

    If you think the battery is ok after charging it should be load tested - I am sure it will fail. Even if the cause of the problem is an alternator issue once a lead acid battery gets this low it is not recoverable.

    Eric Panning
    1981 Seneca III
    Hillsboro, OR (KHIO)

  • You have a digital engine monitor system. While it is very important to monitor the engine and associated parameters (electrical, OAT, GPS position if part of the config.) during flight, the big payoff is data analysis from the recorded information, post flight. Over time, this data will provide you with important trend analysis that could literally save you thousands in engine repair costs by identifying and fixing potential problems early in the game. In your case, the bus voltage is being continuously recorded for each and every flight and you could go back in time to see if and when this electrical issue reared its ugly head.

    There is a website that provides a free service to let you upload your engine data and to permit you to display it in graphical form. We talk about the necessity of preflight inspection to ensure the safety of the planned flight. By the same token, post flight inspection is just as important and the data provided by their service will help keep you safe. Here is a link to the website:


    Also, if the data provided in the analysis points to the source of the problem, then you can avoid the guessing game where you waste time and money ruling out possible causes out one by one.


  • Todd,

    glad you were persistent chasing down the high current reading. Like Eric says, paraphrasing, "An in-flight battery fire could ruin your whole day!"

    It sounds like your A&P is pretty thorough, and will try to figure out if a battery failure was the sole root cause, or if it was secondary to something else happening.

    Speaking of secondary issues, suggest checking your logbooks to see if you are current on the 500 hour alternator clutch inspection. Your alternator is directly coupled to your engine through a rubber-in-sleeve clutch. The clutch will fail either after the rubber ages significantly, or you have a prolonged high-current event during which the clutch transmits its maximum torque for an extended period of time. The consequences of failure are the same as loss of an alternator drive belt, except you can't visually check the clutch as part of the preflight inspection. Continental recently reissued the service bulletin describing the inspection process, which requires removal of the alternator, and measuring the break-free torque with it held in a vice. You might discuss it with your mechanic, although I'll bet he's way ahead of me on this issue!


  • I had a similar problem with my 79 Turbo Arrow IV. After much trouble shooting, an astute mechanic noticed s loose wire touching the external shunt of the gauge behind panel. The wire was to a panel light socket that was no longer used and just dangling. Clipped wire and AMMETER deflection went from full scale to /13 scale deflection. No change in voltages, etc. Not easy to see as I'm not very agile but A & P easily accessed.

  • Thanks for the great info! I am going to try and head to the airport today and pull the data from the Dynon. Not sure if I mentioned the battery was installed new May 2023

  • Cell failures can happen at any time - MORE likely early vs later. What can happen with a failed cell is it provides no current/voltage - only resistance. The charger/alternator cannot tell so all the other cells are overcharged and if AGM you are losing water.

    The same cell failure mode can happen in lithium cells where they are charged in series. The difference is modern lithium cells have miniature battery management systems to shut down the charging to prevent further issues. You would see this as a battery back that only takes a partial charge an fails quickly.

    I would insist on a full capacity test if you are thinking of putting the battery back in. You need it to provide reserve power if the alternator fails and batteries often will continue to start the plane at end of life but have no capacity left to keep the avionics powered beyond minutes.

    If I end up deep discharging a battery I will replace it in the plane and use the old one as a ground power battery with a 12V charger. It is really was at 10.5 V I think it is toast

    Eric Panning
    1981 Seneca III
    Hillsboro, OR (KHIO)

  • I'm pretty sure it was 10.5.

    If the battery is bad, my question is what caused it to go bad.

    Im heading to the airport tomorrow. I'll post after.

    Thanks again everyone.

  • An early failure on a battery (bad cell) is often a manufacturing defect in the battery itself and nothing you have done or could have done to prevent. It can also be caused or accelerated by high vibration... Perhaps a secondary effect from the prop issue?

    A bad cell does fit the symptoms as the alternator would be running hard to try and get it to the right voltage.

    Piper and Cessna should have a built in volt meter from day 1. Your Dynon should display and record this.

    Eric Panning
    1981 Seneca III
    Hillsboro, OR (KHIO)

  • Thanks for the info empannin,

    Sorry for my absence and late reply,

    Here's some new info. I did some testing on the battery. With engine off, I performed an amp draw test. After each reading I added another electrical source.

    Starting voltage. 12.2

    1) Battery switch off. 0 amps

    2) One Skyview on. 8 amps

    3) Two Skyviews and radios on 13 amps

    4) Anti Coll and Landing light (1) 19 amps

    5) Added two wingtip lights. 27 amps

    Volts with all sources on. 12.

    After the test we flew to check it out and the amps were around 25-30 with only the avionics on. Voltage output was around 14.6. After adding the landing lights (3) and cycling the gear, amps went way up, causing the Skyview to give an audible "electrical" warning. I believe the amps were up in the 45-55 range.

    After landing my mechanic thought about lowering the volts at the voltage regulator to see if it would make a difference. He reduced the volts to 13.8. We flew the plane, checked amp draw and low and behold all readings were good. With everything on including landing lights the reading was 26 amps. Cycling the gear pushed it up to around 42 amps then back down to around 27.

    I will have more info later.





  • Hi Todd, do you have halogen bulbs for landing and tip lights? Replacing those will greatly reduce the current draw. Halogen is also voltage sensitive (more volts = more amps).

    13.8 is a better operating point vs 14.6 but 14.6 is still within spec on many planes.

    Any explanation for why the battery went dead? Did they ever load test it?

    For the test with the plane off and max load. You don't have a shorted or failed cell as the battery voltage would have dropped to 10.5V under load.

    Thanks for the updates!


    Eric Panning
    1981 Seneca III
    Hillsboro, OR (KHIO)

  • The Wing tips and the nose landing lights are not led. As for halogen I'm not sure.

    Not sure why it when dead. We did a load test and the results were good. No issues.

    I'll have more later

  • Todd, awesome work on the troubleshooting!!

    Question: Does your TAIII have the earlier charging system design with a separate over voltage relay, or the later design with the over voltage relay incorporated into the voltage regulator?


  • Bob,

    I believe it has the earlier design. I'll find out

  • Bob,

    It is the earlier design. After the adjustment, The high amp issue is resolved.

    Thanks for the help everyone.


  • Hi Todd,

    Thanks for the update. Seeing how you have the earlier charging system design, there's one more test we should do to make sure adjusting the regulator doesn't produce an adverse outcome.

    You'll note the drawing is labeled with Point A (on the bus bar where the circuit breakers originate), and Point B (the input to the regulator). Because your charging system takes its feedback from Point B, Point A on the bus bar will always read slightly higher than the regulator input, with the amount of difference proportional to the amount of current you're drawing from the alternator at any given moment. With all the lights and pitot head running, I'd expect the difference between A and B to be no more than 0.1 volts for a properly operating charging system. The difference should drop to 25 millivolts or less when you shut off all the accessories. I've troubleshot several of these where the difference under full load was as high as 1.5 volts!

    The recommended test is as follows: Connect a pair of voltmeters, one to Point A and one to Point B, and locate them within the pilot's view. Run the engine up to 2000 RPM, and turn on the alternator and all electrical loads - lights, pitot heat, etc. You should see 14.0 to 14.1 on Point A (By the Concorde and Gill specifications for charging their batteries), and a drop of no more than 100 millivolts to Point B. If the drop is greater than 100 millivolts, we should track down the cause. You should also verify the difference between A and B decreases when you remove all the loads. In this case Point A will decrease slightly (but still within the battery charging range of 14.0-14.1), and Point B should hold constant at whatever voltage it read before.


  • Thanks Bob,

    I took a picture of your info on my phone so I can pull it up. When I am able, I'll run this test.

    Thanks again!

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