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  • Help needed figuring out an electric issues in cessna 150.

    Appreciate the collective help and knowledge from folks on this form. Trying to figure out if I am just having a bad EI gauge or if it is something bigger. I am currently asking around on a good A&P, any suggestions would be greatly appreciated.

    So the problem was noted earlier this summer, but due to work I didn't get it looked at right away. Then after looking at the gauge and thinking through the limited electrical knowledge and processes I know, I made the decision to fly it and get it to its wintering spot in Birchwood (from FBX).

    Aircraft is a 1976 Cessna 150, 12 volt system; alternator/battery. So, starting earlier this summer (July) during local touch and go's at Fairbanks, I noticed my EI VA-1A voltage/amp meter reading high, I believe it was in the 30 volt range, but the high voltage light was not illuminated. One would think so and no circuit breakers (CB) were popped.

    Left for about 3 months and returned (October) and needed to get the aircraft to Birchwood. So preflight check evening before I leave the next morning; Master On/Engine Off volts read 119.8 (impossible), discharge light on. No way a 12 volt battery is kicking out 120 volts. Check breakers, wire connectors (were could, not that I really knew what I was looking for), and checked battery fluid level. All looked fine. So I fired her up. Fired up fine, no issues; Master On/Engine On reading 152.9 volts/ 26.9 amps, No High Voltage Light. Thinking no way, no CB's popped, avionics working fine, no smelling burning wires. Decide to do a few TnG's. As I'm taxing, around 800 rpm, discharge light comes on...hmmm...that's weird, never did that before, idle up to 1000+ rpm, light goes out. Bad connector? Do 6 TnG's, volts and amps drop slowly, but still reading high at the end of an hour flight, not the normal 14-ish it normally reads. All avionics working fine.

    Fly home the next day, alls fine besides the excessively high volts and amps. 2.7 to PABV and a beautiful flight. As I'm going along, watching the volts slowly tick down, less and less, until about 2/3's the way home it's steady at 14.2 and holding.

    Plane sits another 10 days, go to do a flight. Master on/engine off, volts read 180-ish, discharge light on, NO high voltage light. At this point I'm like it's got to be the gauge. Fire her up, all is well, starts fine. Master On/Engine on, still reading 180-ish on the volts, but now the discharge light it still on.....hmmmm, alternator failed??? Let her run for about 7 minutes, no fading of the avionics if I where just running off the battery, but then again probably not long enough.

    So check what fuses are under the panel, all's good, nothing looks burnt, so now I'm pretty much stumped and trying to someone who knows electronics.

    Anything I'm not considering may be the issue.....
    Any suggestions on who to take it to at PABV or the surrounding area....

    Appreciate the feedback and help.

    Thanks






    [IMG]http://tapatalk.imageshack.com/v2/14/10/15/f46e96d7c589c171b5858fe1d9e6dfae.jpg

    [/IMG]


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  • #2
    I would start out with a multimeter checking voltage on the battery, bus bar and anywhere else you can first with just the master switch on and then with the engine running around 1000 - 1200 rpm to see what the system is doing verse what the panel EI volt/Amp gauge indicates .

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    • #3
      Also try moving the ground wire for the gauge to another ground point

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      • #4
        Help needed figuring out an electric issues in cessna 150.

        Will try to get on that tomorrow, guessing any multimeter should work right.

        Retrying a couple of the photo's showing the volts reading on the EI


        Master On/Engine On:



        Master on/engine off:



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        • #5
          If it were possible for the Alternator to put out voltage like 152.9v ever light and every piece of electronics would be fried. The problem is you have a bad voltmeter the 152.9 is probably 15.29v. The 119.8v is 11.98v witch would explain why the discharge light came on.

          You may also need to replace the battery.

          What I don't understand is why in hell you left Fairbanks? Are you nuts!!!!!!

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          • #6
            Here's a link to the manufacturer. You can download the installation manual from here. It includes some troubleshooting tips,meter testing, and diagrams...http://buy-ei.com/portfolio/va-1a-voltammeter/. If it turns out the meter internals are hosed and it's multiplying the readings by a factor of 10 I'd check out the charging system also as 15.29 V is going to slow-cook your battery.

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            • #7
              Given the lack of evidence that anything is wrong with anything but the instrument, I'd call EI tech support. I bet they've heard of it before.

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              • #8
                My EI volt/amp gauge was doing the exact same thing when I bought my 172 earlier this year. Call EI and tell them what's happening. They will give you an RMI number to send in the gauge for repair. For $100 total including shipping I had mine totally rebuilt by EI. They are great to deal with, turn around on my gauge was 10 days including shipping time.

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                • #9
                  MacGyver, sounds plausible, but then why would it tick down a normal 14.2 in flight? Battery was brand new in May, but that doesn't necessarily mean anything.

                  AKC172, yup been reading the pdf trying to figure out why it's doing what it's doing. I'm guessing the gauge is bad based on some of my other observations, so I need to get a multimeter on them to start I suppose.

                  Know anyone to fix or replace it?


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                  • #10
                    Mr Pid and OBJ70,

                    Sounds like I'll be giving them a call soon then. Good to hear (not really but you know what I mean) that someone else experienced the same issue and it was resolved rather quickly and inexpensively.

                    Thanks


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                    • #11
                      Without diving into the FAR's, I assume I'll need an A&P to uninstall & install or observe me doing it and sign it off, correct?


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                      • #12
                        Originally posted by Wldlndfirefghtr View Post
                        MacGyver, sounds plausible, but then why would it tick down a normal 14.2 in flight? Battery was brand new in May, but that doesn't necessarily mean anything.
                        At this moment in time it two early to speculate what is wrong with the meter.

                        If the meter was reading correctly except for the decimal-mall point a bad battery charger or connection could give reading of 11.98v or 15.29v.

                        I should have said is have a Avionic tech check the battery and charging system to make sure there not other problems.

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                        • #13
                          I can't disagree with any of the posts so far, but there are a couple of things you can do, troubleshooting wise, before you call EI or contact an A&P. Make sure the round connector in the back of the meter is tight and make sure that the black wire (ground) that goes to that connector is secure on a good ground point. A bad ground on any electronic device can cause some strange behavior. Ray Block (Ray's Aircraft) in Wasilla does my work...no complaints. I don't know any A&P's at Birchwood. Good luck.

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                          • #14
                            Go talk to Mitch at Precision Plus He is water side midfield. He is usually in on Sat. You can take the gauge out no problem its the sign off for putting it back in that counts. If you fly out of Birchwood Mitch is the guy to know.
                            DENNY

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                            • #15
                              Just want to follow up on my thread. It ended up being the gauge, which was pretty suspect from the symptoms. I appreciate everyone's input, as I double checked with a multimeter before sending it off. It's back in and reading perfectly! Thanks all!


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