PA28 BEACON LIGHT FAILURE !!! PLEASE HELP

Discussion in 'Maintenance Bay' started by Davisando, Oct 24, 2020.

  1. Davisando

    Davisando Filing Flight Plan

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    Hello guys. I have a 1979 Piper Archer II and my beacon light went off. I got the A469B (P/N 01-0770044-02) to replace it. Went back to the shop and turns out it didn't work. Mechanic said "box went off". you should get the LED. I've being looking online about the PA-28-181 Archer II beacon light system and found nothing. Can someone please tell me, if I get the LED will it work?, or is there something else not working and would prevent the new "overwhelming" expensive LED not to work. Thank you so much for any help!
     
  2. kgruber

    kgruber En-Route PoA Supporter

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    Have your mechanic fix it.
     
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  3. RyanB

    RyanB Administrator Management Council Member PoA Supporter

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    Not enough information. Did the light burn out or is there a short in the system? A voltage tester should answer those questions. If it’s just isolated to the light assembly, replace with LED.
     
  4. Dan Thomas

    Dan Thomas Final Approach

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    Get the mechanic to check the supply voltage at the box with the beacon turned on. A tired circuit breaker can cause this tye of failure. If he pulls the plug off the box and checks the voltage, it will read just fine, because the breaker's resistance easily passes the few microamps to make the meter read, but not the ten amps or so to fire an incandescent beacon or the two amps to fire a strobe beacon. If the voltage looks good with the box connected, and the thing doesn't work with a new lamp, the box is probably shot.

    Ohm's Law. Ignorance of it causes much money to be spent for no good reason. BTDT.
     
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  5. Davisando

    Davisando Filing Flight Plan

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    Yes, I try to get the mechanic to explain what the problem was, but he didn't. He was busy and troubled for an up landing gear- landing from a client of his. so I felt he wasn't in the mood to deal with me at that moment. So the new bulb is installed and is not working, I will try and do the barker thing to see if it works.
     
  6. WannFly

    WannFly Final Approach PoA Supporter

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    If I recall correctly a new LED becon is $550, if you are choosing to go that route that is.
     
  7. PaulMillner

    PaulMillner Line Up and Wait

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    oh, it's a strobe!

    https://www.skygeek.com/01-0770044-02.html

    Yeah, check the switch, Breaker, the power supply, and the wiring... preferably before spending $200 on a flash tube you may not need... it's not a typical "bulb" that burns out. The suggestion to test under load is a good one! Good luck!

    if you need a new power supply, lots of used ones around these days from folks converting to LED.
     
  8. WannFly

    WannFly Final Approach PoA Supporter

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    If it’s the power supply, the wingtip strobes will be gone too.
     
  9. GRG55

    GRG55 Final Approach Gone West

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    That may be correct on a Piper PA-28, but I would check.
    On my Piper PA-27 the tail strobe has a separate power supply from the wing tip strobes. The system is the OEM from the factory using Whelen components. The tail strobe was an option, which may be why Piper did it that way.
     
  10. Domenick

    Domenick Line Up and Wait

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  11. Dan Thomas

    Dan Thomas Final Approach

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    That manual makes the same mistake so many others do: checking the voltage at the feed wires, which often have to be pulled out of the supply to do so. You don't get a true reading if they're not connected to that box.

    Let's suppose we have a breaker or switch whose old contacts have oxidized (common in old breakers; old switches usually burn). That oxidation is creating a 50-ohm resistance, for instance. The strobe supply needs 2 amps at 12 volts. We can do this two ways: we can divide the voltage by the resistance and see that the breaker willl pass only a quarter of an amp, and the supply won't be happy with that at all, but the meter measuring the voltage needs only a few microamps, or, with my 50-year-old and trusty multimeter, 60 microamps is enough, and it will read pretty good voltage. Or we can divide the voltage by the amps and see that the box has a normal internal resistance of 6 ohms; you can see that adding 50 ohms to it does nothing good for the supply.

    Or we can just connect the box and poke a couple of pins through the insulation on the supply wires and turn the system on and measure the actual voltage the box is getting through that bad breaker (or switch). THAT's where the truth is found.

    So you leave it turned on and crawl under the panel. This is no fun when you're all stiffened up with arthritis like I am. You clip the black lead of your meter to a good ground. You touch the red one to the bus: 12 volts. OK. Touch it now to the hot breaker terminal and see that it's still good, that the screw is bonded to the bus properly. OK. Still good. You touch the red lead to the breaker output terminal: low voltage means a new breaker is in order. If the voltage is still good you touch it to the switch's input from the breaker, the switch's output terminal, and so on and see if there's a voltage drop there. If so, that switch is shot. No voltage drop?? Go back to the tail and measure the voltage between the pin in the wire that was negative when you first checked the voltage there, and the airframe, and see if there's voltage of any sort. If so, you have a bad ground. That can be fun, finding that.

    I used to teach this stuff to my Aircraft Sytems for Pilots students. I don't know how much of it stuck, but evidence tells me that a lot of mechanics didn't get it or it never sank in. Thye start replacing parts until the problem goes away.
     
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  12. Davisando

    Davisando Filing Flight Plan

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    Yea, wingtip strobes do work. One was burned out too, got a new one, installed it and worked fine.
     
  13. Davisando

    Davisando Filing Flight Plan

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    Well.... I already got the "bulb", installed and didn't turn on... thats why I am here now.... Mechanic didn't do a through inspection of the problem and that led me to this position right now. Trying to figure it out
     
  14. 3393RP

    3393RP En-Route

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    I never probe through the insulation on a wire unless it is absolutely necessary. While it's easy to make the argument I'm being ridiculous, breaching the insulation barrier can introduce corrosion, damage the individual wire strands, or weaken the conductor's physical strength.

    I have a few sets of Fluke probes with needle point ends. The hole they leave in wiring insulation is so small that it's very unlikely any damage to the conductor will occur if they are used to puncture the insulation. However, that's just me. I've seen others go so far as using a utility knife to nick open the insulation and then use a standard probe with a tip that's around 1 mm in diameter to measure voltage, current, or ohms in the conductor.

    Of course, I doubt that Dan or any other responsible technician would do that. But it is done by less competent mechanics, and occasionally physical damage may have occurred to a conductor due to friction chafing or pulling the wire into its concealed locations. Because of these possibilities, a good reason may exist to inspect a wire end to end if unexplained anomalies are present in a malfunctioning circuit.
     
    Last edited: Oct 27, 2020
  15. Dan Thomas

    Dan Thomas Final Approach

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    One does what one has to to get the reading one needs. I've used pins to penetrate the insulation. The risk of corrosion in such a place is no bigger than the risk of corrosion where the plug terminals are crimped to the wires. None of these are sealed at all. The only other way to get a reading would be a short adapter harness, with pigtails coming out of it for the meter. It would be plugged in between the airplane's cable and the box. Not too many mechanics are going to make that thing, and it would be very rarely used. I did make alternator/regulator harness with terminals on a chunk of plywood for measuring voltages while running the engine. It helped to isolate charging faults. Even then I used it maybe five times in 25 years.

    Some plugs are open enough at the cable end to push the meter probes into, up against the crimped plug socket.
     
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  16. 3393RP

    3393RP En-Route

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    .

    .

    I should have been more clear. I really wasn't thinking about aviation when I said I never penetrate the insulation on conductors unless really necessary. Over the years, I have worked in many different disciplines that all had complex wiring as a commonality.

    This included large first generation data center UPS systems that used SCRs and TTL logic, multistory commercial HVAC control systems, data and power wiring in very large data centers, and the more mundane, such as the very many boats I've owned over the years.

    In these situations, I have worked in environments where corrosion would manifest itself quickly unless all reasonable precautions were taken. I had this in mind when I made my comments.

    I have read enough of your very informative posts over the years to become quite certain you've never done anything carelessly or halfway just to accomplish a task in less time or with reduced effort, and I didn't mean to imply that.

    I greatly appreciate your contributions to this forum; they have significantly expanded my knowledge of aircraft propulsion, control, and avionics systems. Thank you for that.
     
    Last edited: Oct 28, 2020
  17. Dan Thomas

    Dan Thomas Final Approach

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    Thanks for that.
     
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