Airborne XT trike tach not working

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.

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

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

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.

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.