914 needs two tach sources

by Wayne Lohmeyer in 912 / 914 Technical Questions 5 years ago

We have a 914 with a Woodcomp constant speed propeller. The propeller controller needs the engine RPM and draws from the engine RPM source. Installed a EngiBox to the same RPM source and both displays go blank. I'm told that the EngiBox pulls a 100 Ohm load on the RPM line and it appears that the Woodcomp controller can not handle the extra load.

Any successful solutions to a issue like that?

Thanks!

Re: 914 needs two tach sources

by Bill Hertzel » 5 years ago

Bill Hertzel

13 1.95k 7.97k

My first suggestion would be to reverse the leads at one of the gauges.
The tach signal is AC so there really isn't any (+) or (-), it is just two connections and the two instruments may be fighting each other.
This is only a wild shot in the dark but it is worth a try.

If that doesn't work, try installing a 100Ω resistor in series with one, the other or Both of the Gauges.
If that doesn't work, up the values to 220 or 480Ω.
At some point, at least one or both of them should come alive.
Admittedly, this is all Red-Neck engineering. :unsure:

The EngiBox manual admits that their equipment may not play well with the other devices but otherwise just washes their hands of any wrongdoing.

As a famous man once said, "Son, You're on your own!" :ohmy:

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

Thank you said by: Wayne Lohmeyer

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914 needs two tach sources

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