RPM fluctuations

by Jim Lee in 912 / 914 Technical Questions 4 years ago

The rpm fluctuates from the 4000's up above 5800rpm for a micro second. In other words, the rpm of the engine is not changing, only the rpm indication on the Dynon Skyview, with Dynon lady giving the verbal warning. 921ULS engine. Where is the rpm sender and wire location on the engine, and how do I troubleshoot this?

Thanks!

Re: RPM fluctuations

by Bill Hertzel » 4 years ago

Bill Hertzel

13 1.95k 7.98k

The Rev Counter Trigger Coil (Tachometer Sender) is located within the ignition housing (Generator Assembly).
The White/Grey and Blue/Grey Coil wires exit the ignition housing in the vicinity of the #4 cylinder.
Disconnect and inspect any connections that your installation may have.
A loose wire or poor connection will tend to generate noise that the display interprets as additional pulses causing the high RPM indications.

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

Thank you said by: Jim Lee

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Re: RPM fluctuations

by James Ott » 4 years ago

James Ott

22 334 392

Mine started doing this, so I installed the recommended resistor in the tach wire and it solved the problem. Rotax installation manual, or maybe its the Dynon Skyview installation manual, says you MAY need a resistor and it tells you the recommended ohm value. Its weird because mine worked fine for several years before it started giving erratic rpm readings.

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RPM fluctuations

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