This past weekend I made a couple of short runs to my jabiru 3300. everything went ok but the UMA tachometer (0-3500 electrical) at low rpm was giving erratic readings. I have the DB 9 connector and the wiring was very straightforward, two pins for voltage, one for ground and one for one coil. Am I missing something?, Please anyone with this tach give some input. Thanks in advance.

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G'Day. My dynon does the same goes a bit eratic , cruise is fine, high rpm and low rpm are a little weird .But while the big fan up front keeps going round i dont care


Had similar problem myself, but it was quit a while ago, so can't remember which offending wire it was.

Go back and recheck the wiring schematic & directions -- make sure that everything is wire correctly.

I had one two many wires hooked up -- disconnected it and everything went well afterward.


My Tack drops off to zero when idle speed goes below 800RPM. UMA told me that is normal when using a lighting lead. The only other problem I have is that it is almost impossible to read the hour-meter, the hundredth's and tenth's, the red digits do not show up very well The magnifying lens is worthless. I am considering a separate hour-meter.     Bob Pickens, Troy, Mo.
Try a "Tiny Tach" from Aircraft Spruce. Attach to panel with velcrow tape, then simply wrap the wire lead a few times around a single spack plub lead wire. ..."installation complete". Tiny Tach shows engine rpm digitally when engine running and then show "HOBBS" time when engine shutdown. Cheap, simple and works great. I used one for 10 yrs and never had an issue. Available in 2-stroke & 4-stroke models.

Many thanks to all for your comments.

I agree with Robert on the lousy hour meter, but it will have to do as is. Robert, When you say lighting lead, the tach conects to which of the two leads on the coil, the one going to the switch or to the one going to the distrtibutor?


I will also do what logic and Mack sugests, check the conector  to discard faulty wirings.

best regards,



I connected the "signal input" to one, either, of the wires from the alternator and ahead of the voltage regulator per UMA instructions on "Engine Connections" for a Jabiru engine.        Bob Pickens
I found that connecting to a coil wire did not work well. A alternator wire is better. I suspect using the Jabiru pickup off the flywheel would be the best option. I have not tried that method yet though.


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