fbpx

 

Greetings,  I have an older 2007 912 that is running VERY well.  I recently just developed a problem with the tach meter being intermittent. When it starts working steady, it is fine until I increase the RPM to 3500 and above for a period of time then it starts jumping around between a random number to zero,  after a few seconds it goes to zero and stays there for the duration. It does not come back when restarting the control panel or after shutting down.  But when it does come back it stays for awhile when starting engine, days or a week until I fly again.  I cleaned the wiring contacts going into the module box that takes EGT, CHT, Oil Temp sensor outputs (and tach signal) and sends the communication via 2 wires which I'm assuming is a serial data line to my control panel. I am thinking about taking my oscilloscope out to the hangar and just connect the probes to the two tach wires coming from the engine and cranking the engine with the mags grounded/off  My question is this, what kind of voltage should I be seeing here?   I am really hopeful that I don't need to buy a $1500 panel. 

My setup is a using an AMPtronic SKYDAT GX2

thank you for your suggestions  Jim

9547_1_display.jpg (You do not have access to download this file.)
  • Re: Airborne XT trike tach not working

    by » 2 weeks ago


    I would connect your scope and run the engine, that way you can see if the signal disappears. The ignition section of the heavy maintenance manual has samples of the scope traces that you should expect. As the RPM increases so should the frequency of the pulses and their amplitude. If the singal looks good right into the connector on the tacho instrument then I would carefully open up the unit and look for bad solder joints with a magnifier.

    Let us know what you find.


  • Re: Airborne XT trike tach not working

    by » 2 weeks ago


    Kevin, thanks! I was not aware of the scope samples in the heavy manual!😀


  • Re: Airborne XT trike tach not working

    by » one week ago


    Kevin, It finally warmed up enough so I could open my heated community hangar.  I did the scope (ing?) of the signal from the trigger coil and the signal is good and consistent. I also cleaned the contacts in the connector to the interface module will out any change.

    My former instructor gave me an email address to the owner to the company who manufactured these panels so hopefully he is still around to help out.

     I will keep this thread updated as to the progress.

    Thanks again, Kevin for your help,

     

    Jim Stout


  • Re: Airborne XT trike tach not working

    by » one week ago


    If you are handy with the scope, I would open up the panel and follow the signal lines from the connector and see how far the tacho signal gets in the circuit. You may be able to spot a bad joint or failed component. If you open it up, post some pictures of the top & bottom of the PCB, I might be able to give you some other pointers.


  • Re: Airborne XT trike tach not working

    by » 6 days ago


    Most likely you need a resistor in the tach signal line; I believe about 20K, but best to look up old threads on this very problem. Many of us have had to add the resistor; don't know why it works fine for years then suddenly needs it.


You do not have permissions to reply to this topic.