Electric Tacho Problem
in 912 / 914 Technical Questions
11 years ago
Hi, during a ground run yesterday I noticed a problem with my electric tacho (912ULS). When I first switched on the battery master switch before starting, the tacho, instead of going to the zero position, moved up to approx 1500 RPM. When I started the engine the tacho responded by increasing appropriately for the engine RPM, plus this "extra" reading. ie after start, at an (estimated) idle of 2000 rpm the tacho was reading 2000 + 1500 = 3500 RPM. The tacho responded with normal response to throttle movement, just with this extra reading present. As the engine warmed up the error became less and after shut down the tacho reading with the battery switched on was about 400 RPM. All other electrical instruments were completely normal as was the battery voltage and generator function. It's just the tacho thats affected. It's always been perfect up to now.
Do you think this is simply the tacho gone pear shaped (it's not very old though - about 18 months) or might it be something deeper? At this time of year the plane is living in rather cold and damp conditions - I start it up and run it up to 100 deg oil temp each week (if I've not been able to fly it) to keep it in good order. I was wondering if cold/ damp conditions might affect the tacho instrument?
Cheers, Jon
Do you think this is simply the tacho gone pear shaped (it's not very old though - about 18 months) or might it be something deeper? At this time of year the plane is living in rather cold and damp conditions - I start it up and run it up to 100 deg oil temp each week (if I've not been able to fly it) to keep it in good order. I was wondering if cold/ damp conditions might affect the tacho instrument?
Cheers, Jon
