Many thanks for helping me out with your tacho sensors. Air Dallas received both units and were also very helpful in testing the units and made a working unit out of the 2. However, Rochester guages who are the manufacturer of the unit refused to supply the “Functional Test Procedure” so no testing for certification could be carried out. Rochester reason was that those details belong to Cirrus and if we need one, we should buy a replacement unit from Cirrus which as you know cost around $700. (By the way Cirrus denied the exclusive use and confirmed that the unit is also used in other aircrafts i.e. Seneca or bonanza).
I had one of the unit taken a part, and shockingly witness the poor quality and cheapness of the unit and the way it was put together. I am not surprised the unit fails after so many hours. In our aircraft it was replaced in late 2011 and the unit has lasted about 400 hours. The main component in the unit is a position sensor made by Honewell and retails around $15 (517SS16).
**I can also tell you I have seen bicycle speedo with better quality and reliability than this Tacho Sensor. **Once again, it proves the point that, some manufacturers perceive the aircraft owners to be nice and generous, whom are generally prepared to pay whatever price they ask for and easy to be taken for a ride.
I hope Cirrus are aware of the various problem with this Tacho Sensor not just the quality and price of the unit. The “percentage power” relies on the output from the Tacho generator, so any false feed results in an incorrect calculation of percentage power and the RPM indication, hence possibility of setting up the engine incorrectly.
I am also hoping Cirrus to consider putting time limit on this unit, so it is changed after so many hours, this is to protect the engine from getting abused in flight. An engine that costs over $40k deserves a more reliable instrumentation, than a 60s piece of s…t. design.
Replacing tachos 3 times in 10 years is much more than a coincident!!!