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Thread: Troubleshooting: No power

  1. #1

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    Troubleshooting: No power

    I was troubleshooting no power to my radio and ICS, but now I have no power at all to my aircraft. My electrical is all in the wing root but the battery is under the seat (electrical will be moved this winter, but it's almost summer flying...).

    I'm not sure if I shorted something out. When I flip the master switch, I don't hear the solenoid and nothing comes on. I checked the voltage on either side of the master solenoid, and it seems fine (12.5ish either side). There is power to the master switch, but I don't know if the switch is working.

    As you can tell, I'm not an electrically minded person so any help is appreciated.

    Thanks

  2. #2
    PerryB's Avatar
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    Check your ground cable where it attaches to the airframe. I'm guessing it attaches to the seat frame. I've had that happen on mine, and everything is completely dead when the ground is lost.
    After Monday and Tuesday, even the calendar says WTF !
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  3. #3
    www.SkupTech.com mike mcs repair's Avatar
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    if you show power 12v at master switch with it ON, then the other wire that it connects to is not going to ground like it should.

    edit: providing you have solenoid, and not fuses for main power buss

    pictures would help

  4. #4

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    IMG_8810.JPGIMG_8813.JPG
    Thanks for the responses. I'll check the grounds.

    Here's some pictures Mike. I know the wing root wiring needs to go.




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  5. #5
    cruiser's Avatar
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    If your reading voltage on both sides of the solenoid, the solenoid is open, assuming your reading across the solenoid.

  6. #6

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    Troubleshooting: No power

    Cruiser- I think you are on to something. With the switch off, I shouldn't get any voltage across the solenoid. With the switch on, thats when I should see power on the side that goes to the starter solenoid. Seems like the contractor is closed to let the power go across to the starter post, but maybe I'm confusing terminology.


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    Last edited by flylow; 05-03-2018 at 05:42 PM.

  7. #7

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    Troubleshooting: No power

    So far, I’ve found a poor connection from the solenoid to the master switch (butt connector coming loose). Still troubleshooting.

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    Last edited by flylow; 05-03-2018 at 06:45 PM.

  8. #8
    Eddie Foy's Avatar
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    Non members have fewer privileges. Are you an A&P?
    "Put out my hand and touched the face of God!"

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    I am a member. At least until May 24


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  10. #10
    cruiser's Avatar
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    I provided info on determining whether the master solenoid is open or closed. If you read voltage across your master solenoid it is open. Your volt meter touching both big connections on the solenoid and you see 12 volts, plus or minus, the solenoid is open. Loosen all of those screws on that electrical panel, apply your favorite anti corrosive remedy and see if things improve. A squirt into each wire terminal and a repress would not hurt either.
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  11. #11
    PerryB's Avatar
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    Also, when you check your main ground (I still think that's your problem), just because it's tight doesn't mean its good. Take it off and scrape/brush it clean. At minimum loosen it a bit, twist it back and forth and then crank it down tight. When mine acted up it was completely tight but had no continuity due to paint and arcing.
    Last edited by PerryB; 05-04-2018 at 02:24 PM.
    After Monday and Tuesday, even the calendar says WTF !
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  12. #12
    hotrod180's Avatar
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    Quote Originally Posted by flylow View Post
    I've figured it out-- your battery cables aren't connected!
    Cessna Skywagon-- accept no substitute!
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  13. #13

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    Is there a fuse between the master and the little terminal on the solenoid that actuates it?
    Mine has pretty wimpy blades that hold the fuse in and they are easily corroded. Occasionally I shine these up with 1000 grit sandpaper.
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  14. #14
    wireweinie's Avatar
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    Should NOT be fuses/breakers anywhere in a master circuit! Can't stress that enough!

    Basic circuit: Battery cable from battery positive to the one big post on master solenoid marked 'battery'. The other big post on master solenoid is connected to the start relay and main bus. Since you have only one small terminal on your master, check to be sure the solenoid is marked 'continuous duty', not 'intermittent duty'. The small terminal is connected to one pole of the master switch and then from the switch to ground.

    When the master switch is turned on, the wire from the small terminal is connected to ground. This allows current to flow from ground, through the closed contacts on the master switch, to the small terminal on the solenoid, through the coil, through an internal jumper to the large terminal connected to the battery positive. The magnetic field developed in the coil will pull the contacts closed connecting the two large terminals.

    If you flip the master switch on and don't have power or hear the solenoid actuate, you need to check the circuit from the small terminal on the solenoid, all the way to ground. Connect the ground lead on a voltmeter to a good airframe ground. I'm assuming that you have a clean solid ground connection from battery to airframe. With the master switch off, there should be 12 volts at the small solenoid terminal. with the master switch on, the volts should go to zero. If they do go to zero, there is a problem with the solenoid. If they don't go to zero there is a bad master switch or a bad ground connection for that switch.

    Web
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  15. #15

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    What weenie said. To make it easy, if there is 12 volts both sides of that solenoid, the ground side is simply open. Your wire has either come disconnected, or there is a lot of corrosion under a ground lug somewhere.

    Think about it - a wire with 12 volts on it cannot be connected to the airframe ground. Period. Put a jumper on it to test, then go clean the ground lugs.

  16. #16

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    IMG_0955.JPG

    Dang...tried to edit but deleted...so here it is again

    1951 Supercub. Fused between battery and master..been there for almost 70 years. I know more about brain surgery than electricity but is this a concern??..wirewienie?


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  17. #17
    wireweinie's Avatar
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    That circuit is a completely different design. The 'master' circuit on the original Cub type aircraft did not use a master solenoid. That master circuit is just one pole of a two pole switch. Pushing the toggle up or down will supply bus power by connecting the bus directly to the battery through the switch and one of the two fuses.

    Yes it's been around for 70 years but I don't think it's a particularly safe design. It's hot all the time (unless the battery is disconnected) and it's parked just a few inches away from the right fuel tank. So it's an owners call to keep using it. I always recommend changing over to a master switch/solenoid circuit if you are doing a rebuild or major repairs.

    Web
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  18. #18
    cruiser's Avatar
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    Flynlow, if you a have a “one wire” solenoid, it should be wired the same as #24107 shown below. The coil is internally energized from the batt connection. The master switch grounds the coil, as shown, to complete the circuit and close the coil. Reconnect your battery as normal. Take a short jumper wire and jumper from th small connection to any convenient ground. The negative battery terminal will work fine. The solenoid should close. If it does not, replace it. If it does, replace the master switch.
    Attached Images Attached Images

  19. #19

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    Good idea. Those toggle switches fail with regularity. I have had the one in your photo fail. Tough to replace, unless the panel can be swung inboard from the wing root.
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  20. #20

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    I have also concerns with the proximity of the switch to fuel tank. Doesnt seem like a huge project to relocate...probably $30 project for s good Texas A&P


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  21. #21
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by flynlow View Post
    I have also concerns with the proximity of the switch to fuel tank. Doesnt seem like a huge project to relocate...probably $30 project for s good Texas A&P


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    yup... have known many that have died in otherwise survivable crashes, from a fire starting up in wing root, because of the sparks/gas... ALL electrical get moved from the wing root in every rebuild I do...

  22. #22

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    Troubleshooting: No power

    Thanks for all the help.

    It is a continuous duty solenoid. You can’t see the other post. I figured out all of my confusion. The master switch doesn’t ground the system. It’s wired differently. The landing light CB is tied to the master switch and to the landing light solenoid. Both of the posts on the master solenoid came to the master switch. And the master switch doesn’t go to a ground. I’m rewiring it like the PA18 schematic.






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    Last edited by flylow; 05-08-2018 at 02:02 AM.
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  23. #23

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    I have experienced this twice now and would like to avoid a third experience. When temps drop to 20F or below I have experienced odd electrical characteristics. I have confirmed viability/continuity of the breaker, single pole single throw switch, battery voltage 13.12VDC and all checks out just fine. When temps are above freezing, no issues ever. So problem I exeperience is when it is real cold and plane sits outside for a few hours. I go to turn master switch on and nothing happens. Master relay does not engage and no power supplied to main bus. Starter push button is somewhat tacky. Only thing I can think of is that the master relay somehow has water/condensation inside and when it freezes it prevents relay from engaging. The remedy is to hand start the engine, go fly with cabin heat on and after 5 minutes of flying or so the electrical system comes alive. So to summarize, no problems ever when temps above freezing. Problem has occurred when temps were well below freezing and cabin area unheated for 2 or more hours. I am going to replace the master relay/solenoid and observe any symptom changes.

  24. #24
    mvivion's Avatar
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    Quote Originally Posted by bjh356 View Post
    I have experienced this twice now and would like to avoid a third experience. When temps drop to 20F or below I have experienced odd electrical characteristics. I have confirmed viability/continuity of the breaker, single pole single throw switch, battery voltage 13.12VDC and all checks out just fine. When temps are above freezing, no issues ever. So problem I exeperience is when it is real cold and plane sits outside for a few hours. I go to turn master switch on and nothing happens. Master relay does not engage and no power supplied to main bus. Starter push button is somewhat tacky. Only thing I can think of is that the master relay somehow has water/condensation inside and when it freezes it prevents relay from engaging. The remedy is to hand start the engine, go fly with cabin heat on and after 5 minutes of flying or so the electrical system comes alive. So to summarize, no problems ever when temps above freezing. Problem has occurred when temps were well below freezing and cabin area unheated for 2 or more hours. I am going to replace the master relay/solenoid and observe any symptom changes.
    Judging from the "Location" noted on your post, moisture in an electrical component seems pretty likely.

    MTV
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  25. #25

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    I live in Unalaska but do most of my flying in SE AK. Unfortunately no place to store a cub in these parts. The recent issue occurred at 4,500 feet MSL outside Juneau with OAT of 0 F.

  26. #26
    www.SkupTech.com mike mcs repair's Avatar
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    yup replace master, has moisture in it.... to verify heat it with a hair dryer

  27. #27
    wireweinie's Avatar
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    Master relay. I've seen this regularly in extreme cold.

    Any idea how old the relay is?

    Web
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  28. #28
    BC12D-4-85's Avatar
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    Click......click click click click...nothing. Hmmm?

    Many years ago local mechanics had a pet fix besides replacement. Some would drill a vent and dry on the hangar's furnace then reseal with glue. Some suggested leaving them unsealed so they could evaporate the insulating moisture. Others said leave the master on while pre-flighting and it'd warm up and work. I used to buy new ones at M&O auto supply and keep a spare. And carried a small jumper cable with clamps just in case it was too cold to fuss with fixing.

    What's the latest on how to deal with it?

    Gary

  29. #29

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    Don't know the age of relay.

  30. #30
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    I had my starter contactor stick last week on a cold day. I assumed moisture in it too or something broke. When it worked again the next day after it got warmer, ice seemed most likely to be the cause. I bought a new starter contactor but haven’t installed it yet. And prophylatically I am putting in a new continuous duty master contactor too.
    "Fast is fine, but accuracy is everything." Wyatt Earp

  31. #31
    skywagon8a's Avatar
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    At least it failed in the open position. How would you like to be drifting across a pond in a 185 with the wind blowing and have the starter relay stick closed after starting? Shut it down, turn off the master, climb up on the nose, take off the top cowl, beat the crap out of the relay with a screw driver, reinstall the cowl, get back in and start the engine before running aground on the downwind shore? Solution, get rid of the crap Cessna relay and replace it with a Cole-Hersey. These are made locally by the way.
    N1PA
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  32. #32
    spinner2's Avatar
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    Quote Originally Posted by skywagon8a View Post
    At least it failed in the open position. How would you like to be drifting across a pond in a 185 with the wind blowing and have the starter relay stick closed after starting? Shut it down, turn off the master, climb up on the nose, take off the top cowl, beat the crap out of the relay with a screw driver, reinstall the cowl, get back in and start the engine before running aground on the downwind shore? Solution, get rid of the crap Cessna relay and replace it with a Cole-Hersey. These are made locally by the way.
    That would not be fun at all. And could be an easy way to loose cowl parts.

    Mine did stick in the closed position. The master switch then became the starter switch.

    I had this happen in a Cessna once too with the original contactor and in the closed position. A friend and I flew into Fish Lake Idaho and when we left it stuck. Same deal; the master became the starter switch. Realizing what happened I turned the master off when it started and flew home without electrical. This wasn’t an ice issue, it was summer time.

    Dealing with it in front of the hangar is much easier.
    "Fast is fine, but accuracy is everything." Wyatt Earp

  33. #33
    skywagon8a's Avatar
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    Or another time when taxing from the dock to a mooring, pulling the mixture and finding the engine still turning with the starter?
    N1PA

  34. #34

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    Sometimes a low voltage (battery) condition can cause contacts inside solenoid to “weld” themselves together and stick when activated.
    Not sure of the physics behind this but I’ve seen it happen a few times.

  35. #35
    wireweinie's Avatar
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    Quote Originally Posted by skywagon8a View Post
    At least it failed in the open position. How would you like to be drifting across a pond in a 185 with the wind blowing and have the starter relay stick closed after starting? Shut it down, turn off the master, climb up on the nose, take off the top cowl, beat the crap out of the relay with a screw driver, reinstall the cowl, get back in and start the engine before running aground on the downwind shore? Solution, get rid of the crap Cessna relay and replace it with a Cole-Hersey. These are made locally by the way.
    This situation is another argument for installing a master relay to replace the original Piper master switch. A stuck start relay can simply be shut off by shutting off the master relay as the master is in series with the start relay. If you have the original Piper master switch, the 'master' is just a switch that provides power to the main bus. The start relay is connected directly to the battery. In that system, with a stuck start relay, there's not much you can do except let the battery go dead and hope you don't burn up the starter.

    Web
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  36. #36
    BC12D-4-85's Avatar
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    I had a starter solenoid stick on a '79 C-185. 24V system with battery in the baggage, starter contactor on the firewall. Taxiing on floats while alone 150 miles out in the Bush in the middle of a lake. Only indication was a pegged ammeter.

    Shut down master switch and stopped starter. Too far to paddle to shore and no way to charge a dead battery. No radio contact with mechanics. Did Skywagon's post #31 after reading owner's manual wiring diagram and following the big wire back from the starter to a relay. Mosquitoes and I beat on assumed faulty component a few times until it unstuck. Carried a spare from then on.

    Gary
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  37. #37

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    This issue seems more common than I realized. I've had it happen both ways. Once, on skis a long way from help, turned the key and nothing, not even a click. I hand propped it to start and get out of there, and found out later about the "hit it with something" method. Another time, fortunately at home, the master became the starter.

  38. #38
    skywagon8a's Avatar
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    This is beginning to sound like the old mechanics joke: "Use a bigger hammer"!
    N1PA

  39. #39
    hotrod180's Avatar
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    Them old mechanics knew their stuff!
    Cessna Skywagon-- accept no substitute!
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  40. #40
    aktango58's Avatar
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    Quote Originally Posted by skywagon8a View Post
    Or another time when taxing from the dock to a mooring, pulling the mixture and finding the engine still turning with the starter?
    Reading your two stories, your 185's value just went down $0.10!

    Bryan, I had far fewer issues once I moved into a hangar. One of the big changes I did make though was to ensure I had the door open and a fan running at least some of the time to blow air through the hangar and plane. The breeze would dry stuff out much better than heat, duh, and keeping/getting the plane dry reduced my failure rate immensely. I spent summers on floats also.

    I like the drill and dry method. Lots of electrical stuff gets fixed sitting on the furnace. Even some solid state stuff seems to improve once you get them dry.
    I don't know where you've been me lad, but I see you won first Prize!
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